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Past Events

An asterisk (*) indicates an MCC-sponsored event.

Lectures and Talks (59)
MCC Visitors (55)
Conferences, Workshops, and Summer Schools (296)

Lectures and Talks

Wednesday, February 6, 2008 Quantum coherence and energy transfer: Quantum dot arrays and photosynthetic complexes*

Location: 1003 MRL, 11:00 am
Presenter(s): Alan Aspuru-Guzik,Assistant Professor, Department of Chemistry and Chemical Biology, Harvard University
Contact: Amy Young
Description: Our research group is interested in theoretical engineering and design of novel organic and nano-organic photovoltaic devices. In this talk, I will discuss a novel approach to understand the role of quantum coherence in excitonic energy transfer of biological systems. The interplay of quantum coherence and decoherence can be employed to direct energy transfer. I will talk about how to apply these concepts to quantum dot arrays and explore the potential use of these excitonic engineering techniques for solar cells and quantum information.

Thursday, October 18, 2007 Nanoscience and Computer Science in Costa Rica: the National Initiative, Projects and Possible Collaborations*

Location: 201 MRL, 1:00 pm
Presenter(s): Santiago Nunez-Corrales, National Collaboratorium for Advanced Computing and National Center for Advanced Technology Studies
Contact: Jeongnim Kim, jnkim --> uiuc.edu
Description: During the last decade nanotechnology has shown a constant growth in both theory and applications, becoming a leading edge area and a strategic component for economic development. Costa Rica has committed to forge a national space for nanotechnology and nanoscience through CeNAT by strengthening collaborations with local and international partners, building an increasingly strong research facility (LANOTEC, Nanotechnology Laboratory) and developing projects that tackle basic and applied problems within the field. Current projects tie experimental approaches with high performance computing simulations as well as statistical and mathematical modeling of nanoscale events. The four main areas of work are (a) micro and nanoscale devices, (b) surface modification of materials (c) characterization and production of nanostructures (d) integration of a computational simulation and optimization platform for research in nanoscience and nanotechnology. A detailed description of the architecture and goals of the computational platform is given as well as links for collaborations on the intersections with projects developed by MCC at NCSA as the OHMMS package and other points of interest.

Thursday, September 27, 2007 Atomistic theory of the electronic and optical properties of self-assembled quantum dots*

Organization: University of Illinois at Urbana-Champaign
Location: Room 280 MRL Materials Research Lab, 1:00 pm
Contact: Jean-Pierre Leburton, leburton@ceg.uiuc.edu
Description: A multiband microscopic theory of many-exciton complexes in self assembledquantum dots is presented. The single particle states are obtained bythree methods: single-band effective-mass approximation, the multiband kpmethod, and the tight-binding method. The electronic structure calculations are coupled with strain calculations via Bir-Pikus Hamiltonian. The many-body wave functions of N electrons and N valence holes are expanded in the basis of Slater determinants. The Coulomb matrix elements are evaluated using statically screened interaction for the three different sets of single particle states and the correlated N-exciton states are obtained by the configuration interaction method. The results of the single-band effective-mass approximation are successfully compared with those obtained by using the of kp and tight-binding methods. The theory is applied to the study of the electronic structure and optical properties of a single InAs quantum dot grown on InP patterned substrate. The effect of positioning of quantum dots using a nanotemplate on their optical spectra is determined by a comparison with dots on unpatterned substrates, and with experimental results.

Thursday, January 25, 2007 Google’s PageRank and Beyond: The Science of Search Engine Rankings*

Location: Room 126 Graduate School of Library and Information Science, 12:00 pm
Presenter(s): Professor Amy Langville, College of Charleston, South Carolina
Contact: Amy Young, amyoung --> uiuc.edu, (217) 333 - 0512
Description: Amy Langville is co-author of "Google’s PageRank and Beyond: The Science of Search Engine Rankings" (May 2006, Princeton University Press), the first book ever about the science of Web page rankings. The book serves two very different audiences: the curious science reader and the technical computational reader. This brownbag will cover topics of interest to webmasters, and answer such questions as: Why doesn’t your home page appear on the first page of search results, even when you query your own name? How do other Web pages always appear at the top? What creates these rankings? And how? How do search engines make money? How does the Great Firewall of China influence research? Amy is Assistant Professor of Mathematics at the College of Charleston. She studies mathematical algorithms for information retrieval and text and data mining applications. This brownbag is sponsored by the Materials Computation Center, and Women in Computer Science, and CITES (UIUC).

Thursday, January 25, 2007 Algorithms behind search engines*

Location: Room 2405 Siebel Center, 201 North Goodwin Ave., Urbana, 7:00 pm
Presenter(s): Professor Amy Langville, College of Charleston, South Carolina
Contact: Amy Young, amyoung --> uiuc.edu, (217) 333 - 0512
Description: Amy Langville is co-author of "Google’s PageRank and Beyond: The Science of Search Engine Rankings". Amy will present at the Women in Computer Science general meeting on the topic of algorithms behind search engines. This talk is suitable for someone interested in applied math and CS topics, or for someone building their own search engine. This presentation is sponsored by the Materials Computation Center. Women in Computer Science, and CITES (UIUC).

Friday, December 8, 2006 Multiscale modeling of Defect Mechanisms in Materials for Nuclear Energy Applications*

Location: Room 280 MRL, 2:30 pm
Presenter(s): Dr. Chaitanya S. Deo, Los Alamos National Laboratory
Contact: Dallas Trinkle, dtrinkle --> uiuc.edu
Description: The key to developing advanced materials for nuclear applications is in understanding the interplay between the various physical scales present, from atomic level interactions, to microstructural composition and macroscale behavior. Defect mechanisms at the atomic scale determine the microstructure and ultimately, a whole host of macroscopic properties, including radiation resistance, strength, ductility, toughness, thermal conductivity etc. This talk focuses on the mechanics and kinetic properties of point defects (vacancies, interstitials, external atoms, voids) and line defects (dislocations) in materials used for nuclear applications. Computational algorithms and techniques including Monte Carlo, molecular dynamics and linear elasticity are used to connect nanoscale defect mechanisms to their macroscopic manifestations. I examine how defects behave in nuclear fuel (hyperstoichiometric uranium dioxide) and structural materials (iron and ferritic steels) under ambient and radiation damage environments, such as those present in a nuclear reactor. In the case of nuclear fuel, oxygen interstitial migration in hyperstoichiometric UO2 is investigated using kinetic Monte Carlo and accelerated dynamics techniques. Diffusivity of oxygen interstitials is calculated as a function of temperature and non-stoichiometry and compared to experimental data. In the case of structural materials, namely ferritic steels, hierarchical modeling techniques are employed to ultimately predict yield stress dependence on irradiation dose. Irradiation creates damage, in the form of interstitials and vacancies, and may create transmutation gases such as helium and hydrogen. The results of molecular dynamics and Monte Carlo simulations suggest that extrinsic gas atoms such as helium stabilize voids into bubbles that may precipitate fracture of structural materials in radiation environments. The interactions of clusters and bubbles with dislocations influence mechanical properties such as work hardening, flow stress and yield stress under ambient and radiation environments. Results from the MD/KMC simulations are used to parameterize an irradiation hardening model within the framework of a viscoplastic self consistent code (VPSC) which simulates the plastic deformation of polycrystalline aggregates subjected to external strains and stresses. The stress dependence on irradiation dose is calculated and compared to experimental data obtained following high energy radiation damage in T91 (ferritic) steel.

Friday, November 3, 2006 High Pressure Physics of Correlated Materials: Experiment and Theory at LLNL and UCD on Gd and MnO*

Location: 280 MRL, 3:00 pm
Presenter(s): Professor Warren Pickett, University of California - Davis
Contact: Richard Martin
Notes: This is a joint MCC and PGSA Graduate Student Colloquium.

Wednesday, November 1, 2006 Treating Manybody Polarization and Manybody Dispersion in Complex Systems: The Quantum Drude Oscillator Formalism*

Location: 3269 Beckman Institute, 11:00 am
Presenter(s): Dr. Glenn Martyna, IBM TJ Watson Laboratory, Yorktown Heights, New York
Contact: Joyce Lucas, joyce --> ks.uiuc.edu
Description: There are many physical systems where the nonpairwise additive nature of polarization and dispersion interactions becomes very important, in particular, the complex heterogeneous systems of interest in chemistry, biology and physics. For example, the dipole moment of water changes from 1.85 Debye in the gas phase to approximately 3 Debye in the bulk liquid and attains intermediate values at hydrophobic interfaces due to manybody polarization. Similarly, although the bulk properties of hydrophobic fluids can be modeled using a pair potential, this underestimates the surface tension by 30% due to manybody dispersion interactions. In order to model both the full manybody polarization and dispersion interactions in atomic and molecule systems, a system of quanized Drude oscillators is introduced and a O(N) simulation method based on quantum path integrals described. Application to liquid xenon is given.
Notes: This seminar is supported by the Theoretical and Computational Biophysics Group at Beckman Institute and the Materials Computation Center.

Friday, September 15, 2006 Simulation of unconventional electronic phases by Quantum Monte Carlo*

Presenter(s): Sandro Sorella, SISSA/ISAS, Trieste Italy
Contact: Michele Casula, casula --> express.cites.uiuc.edu
Description: We discuss several examples where QMC can describe genuine new phases of matter, that are not described by any weak coupling mean field theory. Examples are d-wave superconductivity in repulsive models, Mott insulating physics and spin liquid behavior in frustrated spin models. In all these cases Quantum Monte Carlo allows to describe faithfully the electron correlation. This is achieved by first optimizing the energy of an highly correlated many-body wave function. The stability of various new phases of matter obtained with the variational approach is then tested by applying the Diffusion Monte Carlo (DMC) projection technique to the exact ground state.[2] Due to very important advances[3] in the energy optimization of strongly correlated variational wave functions, recently it has been possible to perform with this approach a realistic and accurate simulation of aromatic compounds[4], where the major role of the correlation comes from the Resonating Valence Bond character describing the Benzene ring[3,4]. [1] M. Casula, C. Attaccalite and S. Sorella J. Chem. Phys. \bf 121 7110 (2004). [2] see e.g. M. Casula, C. Filippi, and S. Sorella, Phys. Rev. Lett. Phys. Rev. Letters, \bf 95, 100201 (2005), for a recent extension of DMC. [3] S. Sorella, Phys. Rev. B 71, 241103 (2005), see also C. J. Umrigar and C. Filippi PRL 94, 150201 (2005). [4] M. Casula, D. Rocca, and S. Sorella in preparation.
Notes: This talk is jointly sponsored by the Physics Department and the MCC.

Wednesday, September 6, 2006 Determination of intrinsicswitching field distributions inperpendicular recording media*

Location: Room 280 MRL, 10:00 am
Presenter(s): Dr. Andreas Berger, Hitachi Global StorageTechnologies, San Jose Research Center, CA
Contact: Karin Dahmen, dahmen --> uiuc.edu
Description: In perpendicular magnetic recording, one of the most crucialproperties defining the quality of a recording media is the intrinsic switchingfield distribution D(HS) of the media grains [1]. This property, which is mostlyimpacted by the anisotropy field HK and orientation distributions of the media grains, is so important, because it limits the definition of the recordedtransitions in a bit pattern. Thus, it is ultimately responsible for theachievable recording density [2]. Hereby, it is important to realize that it isnot the macroscopic switching field distribution Dm(HS) in a uniformly applied field that is relevant, but the local distribution Dl(HS) of switchingfields in a recording process, which takes place in a narrowly defined fieldgeometry. We have developed a magnetometry method for the experimentalcharacterization of D(HS) in perpendicular media and studied its reliabilityand precision by means of experiments and micromagnetic simulations [3,4].The method is based upon a comparison between the major loop and a set of recoil loops, which start at a certain distance _M away from saturation. Inparticular, we measure the applied field difference _H between the variousrecoil loops and the major loop for identical M-values, i.e. the same averagedemagnetizing fields. By analyzing complete _H(M,_M)-data sets from multiple recoil loops, we gain a refined measure of the entire switching fielddistribution D(HS) [4]. Such detailed knowledge of D(HS) is very important,because key media characteristics are defined by the tails of the switchingfield distribution rather than its center. For instance, it is the high-end tail of D(HS) that contributes most to the overwrite value of recording media andthe overall reliability of repeated recording.

Thursday, March 9, 2006 The role of first principles calculations in multiscale simulations of iron under irradiation*

Location: 280 MRL, 1:00 pm
Presenter(s): Francois Willaime, Service de Recherches de Metallurgie Physique, CEA/Saclay, France
Contact: Pascal Bellon, bellon@uiuc.edu
Description: Changes in microstructure and mechanical properties of materials under or after irradiation are governed by the kinetics of defects produced by irradiation. Performing a predictive simulation of these complex phenomena requires a multi-scale approach, where the atomistic properties of defects are determined by first principles calculations and then used as input data for kinetic simulations covering macroscoping time and length scales. The recent advances obtained in iron will be presented. Efficient DFT-GGA codes, like the SIESTA code based on localised basis sets used in this study, now allow performing almost routinely calculations on systems which are large enough (up to 250 atoms here) to study the structure and migration mechanism of small defect clusters. The properties of interstitial- and vacancy-clusters with up to four defects have thus been determined. At variance with previous predictions based on empirical potentials, we find that interstitial clusters, with up to three interstitials, are made of <110>dumbbells and migrate by a three dimensional mechanism with a migration energy of 0.3-to-0.4 eV and not by fast one dimensional glides. Unexpected results are also found for vacancy-clusters: the tri- and quadri-vacancies are found to have lower migration energies than the mono-vacancy. The defect population evolution upon isochronal annealing after electron irradiation has then been determined by Kinetic Monte Carlo. A very conclusive agreement with experiments is obtained. Other examples of defect-complexes involving carbon (for steels) and helium (for fusion-reactor materials) will be shown. Empirical potentials are still necessary for larger scale atomistic simulations; their improvement by including first-principles results on defect properties in the database of the fit will be described.

Thursday, December 15, 2005 Statistical Physics of Fracture*

Location: 201 MRL, 1:30 pm
Presenter(s): Phani Kumar V.V. Nukala (Computer Science and Mathematics Division, Oak Ridge National Laboratory)
Contact: Eric de Sturler, sturler@cs.uiuc.edu
Description: Using large scale numerical simulations and extensive statistical sampling, we consider the statistical properties of fracture in two- and three-dimensional discrete lattice models, in particular, the random fuse model. Computational modeling of fracture in disordered (heterogeneous) media using discrete lattice models is often limited to small system sizes due to high computational cost involved in re-solving the governing system of equations every time a new lattice bond is broken. For two-dimensional simulations, we use an efficient algorithm based on multiple-rank sparse Cholesky downdating scheme. Based on the proposed algorithm, we present simulation results for large 2D lattice systems (e.g., L 1024). For large-scale 3D discrete lattice simulations, we adopt an iterative scheme using block-circulant preconditioner. Based on these simulations with strong disorder, we analyze important statistical properties of fracture; namely, damage localization and its deviation from percolation behavior, scaling laws for damage density, avalanche precursors, universality of fracture strength distribution, size effect on the mean fracture strength, and finally the scaling of crack surface roughness. Acknowledgments This research is sponsored by the Mathematical, Information and Computational Sciences Division, Office of Advanced Scientific Computing Research, U.S. Department of Energy under contract number DE-AC05-00OR22725 with UT-Battelle, LLC.

Monday, December 12, 2005 Kinetics and thermodynamics of hydrides for reversible hydrogen storage*

Location: 280 MRL, 1:30 pm
Presenter(s): Roland Stumpf, Materials Physics, Sandia National Labs
Contact: Duane D. Johnson, duanej@uiuc.edu
Description: Hydrogen is considered by many as the transportation fuel of the future. Hydrogen storage is maybe the main challenge to make this vision a reality. One way to store hydrogen is in reversible hydrides. These are considered competitive with gasoline if they hold about 10 weight % hydrogen that can be released at about 100 C and re-absorbed within 5 minutes at pressures below 100 bar. I will show how first principles electronic structure theory can aid in discovering new hydrides with high H content and a thermodynamic stability compatible with the quoted temperature and pressure range. The screening of hydrides starts with a choice of a stoichiometry and a set of compatible trial structures from the ICSD crystallographic database. These structures are then relaxed and their temperature dependent free energy is calculated within DFT/GGA and the harmonic approximation. I will discuss what to do when the harmonic approximation fails and how the theoretical results compare with experiment. This approach identifies two promising hydrides, MgB2H8 and CaB2H8. The second part of the talk will cover theoretical and some experimental result suggesting a surface mechanism for Ti activation of H sorption in NaAlH4. The field of using complex simple metal hydrides for hydrogen storage got started ten years ago when it was discovered that small amounts of transition metals, especially Ti, made the H desorption from NaAlH4 reversible. I propose that a H stabilized Ti-Al near surface alloy at the ubiquitous Al phase lowers the barriers for H2 dissociation and recombination, which is the rate limiting step in H2 sorption at NaAlH4.

Wednesday, November 9, 2005 Numerical methods (and some analysis) for material science applications*

Location: 2240 DCL, 3:00 pm
Presenter(s): Dr. Richard B. Lehoucq, Sandia National Laboratories
Contact: Eric de Sturler, sturler@cs.uiuc.edu, (217) 244-6720
Description: My presentation provides an overview of preliminary work in collaboration with the multiscale computational materials methods department at Sandia National Labs. This work includes electronic structure computations, multilevel methods for molecular dynamics and an analysis of atomistic-to-continuum coupling schemes.

Monday, October 24, 2005 Excited states in semiconductors and insulators: ab inito quasiparticle bandstructures of II-VI compounds, group-III-nitrides and high-k dielectrics*

Location: 3110 Engineering Sciences Building, 1:00 pm
Presenter(s): Dr. Patrick Rinke, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
Contact: Kris Delauney, kdelaney --> uiuc.edu
Description: Photo-electron spectroscopy has developed into an invaluable experimental tool for the study of electron excitations in bulk solids and surfaces. The success of photoemission spectroscopy (PES) and its inverse counterpart (IPES) owes much to the interpretation of the photo-electron spectra in terms of single-particle excitations or quasiparticles. For solids Hedins GW approximation, where G refers to the Greens function and W to the dynamically screened Coulomb interaction, has become the method of choice for an ab initio calculation of the quasiparticle energy spectrum. GW is typically applied as a perturbation to density-functional theory (DFT) in the local-density approximation (LDA), however, for systems with semicore d-electrons for instance this approach proves to be problematic if pseudopotentials are used. In this work we therefore combine GW with DFT in the exact-exchange (EXX) approach and present a systematic ab initio study of the electronic structure of selected II-VI compounds and group III nitrides, which are important materials for the optical industry. We show that EXX gives an improved description of the d-electron hybridization compared to the LDA. Moreover, we find that it is essential to use EXX pseudopotentials [1] in order to treat core-valence exchange consistently. In combination with GW we achieve very good agreement with available photoemission data. Since the DFT energies and wavefunctions serve as input for the GW calculation we conclude that for these materials EXX constitutes the better starting point [2]. [1] M. Moukara, M. Staedele, J.A. Majewski, P. Vogl, and A Goerling, J. Phys.: Condens. Matter 12, 6783 (2000). [2] P. Rinke, A. Qteish, J. Neugebauer, C. Freysoldt, and M. Scheffler, New J. Phys. 7, 126 (2005).

Tuesday, August 30, 2005 Current technical issues for vertical quantum dot devices

Location: 3110 ESB, 1:30 pm
Presenter(s): D.G. Austing, NRC, Ottawa, Canada
Contact: J.-P. Leburton
Description: I will explore a number of relevant experimental issues concerning vertical quantum dot structures. These include: 1. Ground and excited states in circular and non-circular single dot mesa structures. 2. 0D-0D resonant tunneling in weakly vertically coupled double quantum dot structures. 3. Triple quantum well structures for possible investigation into super-exchange. 4. Progress report on laterally coupled vertical quantum dots.

Thursday, April 21, 2005 Modeling in the Middle: Design of Competent and Efficient EvolutionaryAlgorithm

Location: 280 Materials Research Laboratory, Urbana, 12:00 pm
Presenter(s): Kumara Sastry, Illinois Genetic Algorithms Laboratory, Department of Materials Science and Engineering UIUC
Description: Genetic and evolutionary algorithms are complex conceptual machines which have been effectively used to solve complex search and optimization problem across a broad spectrum of areas. Traditionally, practitioners have often used ad-hoc methods to develop operators and to set parameters of evolutionary algorithms. On the other hand theoreticians develop exact and accurate models of genetic algorithms which are often opaque and does not avail themselves for scalable aglorithm design. In contrast, an engineering approach of using principles of design decomposition, facetwise and dimensional models is very useful in not only understanding the scalablity, but also in the design of scalable evolutionary algorithms. I’ll illustrate this modelling-in-the-middle approach for predicting the scalability and parameter setting of evolutionary algorithms with particular application to multiscale modeling in materials science and excitation chemistry.

Monday, April 4, 2005 Towards materials specific simulations of high temperature superconductors*

Location: 280 MRL, 12:00 pm
Presenter(s): Paul R. C. Kent / University of Cincinnati
Contact: Richard Martin, rmartin@uiuc.edu
Description: Since the discovery of high temperature superconductivity in the cuprates there has been a constant stream of new experimental and theoretical papers. However, although these materials are entering industrial use, the mechanism of superconductivity in these materials remains elusive. In this talk I shall first give an overview of these materials, and then discuss progress in simulating these "strongly correlated" materials computationally using "LDA+" techniques such a LDA+DCA. Cluster-based theories such as the dynamic cluster approximation (DCA) have recently predicted phase diagrams close to those seen in experiment for the Hubbard model, but require parameters for the underlying Hamiltonian. I will give an overview of the challenges involved in obtaining parameters from density functional theory for these simulations and present results for the parameter dependence of the superconducting transition temperature for realistic models of the cuprates.

Monday-Friday, February 14-25, 2005 36th Spring School 2005: Magnetism goes Nano (Electron Correlation, Spin Transport, Molecular Magnetism)

Location

Juelich, Germany

Contact

Stefan Bluegel, [+49]-2461-61-4249

Register before

Friday, December 3, 2004

Registration cost

320.00 euro

Description

The Forschungszentrum Juelich has a long tradition in organizing these spring schools, which covered over the years a large spectrum of active subjects in condensed matter research. The lecture focus particularly on students and PhD students in physics and related areas, such as chemistry and material science.

There is no conference fee and the book which goes with the lectures is free of charge. Low-cost accomodation has been arranged at the youth hostel in Aachen.

Note: with support of an NSF grant, the MCC offers assistance with travel funds for this event. See http://www.mcc.uiuc.edu/travel for details.

Monday, December 6, 2004 Dielectric Properties of Semiconductors by TDDFT*

Location

3110 ESB, 10:00 am

Presenter(s)

Nobuhiko Akino, Sumitomo Chemical Company

Abstract

Time-dependent density-functional theory (TDDFT) has applied to the dielectric responses of the semiconductors such as C, Ge, Si, and AlGaAs. In our study, the real-space grid representation is used for the electron wavefunctions. In the calculations of the dielectric responses, the real-time approach is employed where we follow the linear responses of the systems under externally applied perturbations in the real time. Both the static and dynamic dielectric functions are calculated. Especially, the static dielectric constants E(0) are good agreement with the experimental values. The effect of components in the compound semiconductor AlGaAs including AlAs and GaAs is also studied and we have found that the static dielectric function reflects the energy band separation.

If time permits, Dr. Akino will also cover "Study of PLED by TDDFT and Device Simulation"

Polymer light emitting diodes (PLEDs) have been of interest for displays and other lighting applications. The low cost and the ease of processing are the advantages of the conjugated polymers over the inorganic materials and the low molecules as the former can be deposited by spin-coating over large area. Moreover, the color tuning and efficiency are considered to be controlled by the manipulation of the molecular structures. These make the conjugated polymers good candidates in the LEDs and other applications.

The simplest PLED consists of the polymer layer sandwiched between the cathode and the anode. The radiative recombination of the injected electrons and holes in the polymer layer results in the emission of light. The emission spectrum is determined by the nature of polymer and the device optimization requires us to understand the fundamental physics of the charge injection, transport, and recombination. Thus, it is essential to study from both the material design and the device optimization to achieve better LEDs.

We have studied the spectra of the polymers by the time dependent density functional theory (TDDFT) in the real space and the real time formulation. Since a real polymer is too large to handle, we have performed the calculations of the oligmers with different length and attempted to extrapolate the properties in the polymer. For the PLED device, we have also performed the device simulation based on the band model, from which we are able to obtain the information such as the carrier density inside the device.

Thursday, December 2, 2004 Finite-Element Method for Large-Scale Ab Initio Electronic-Structure Calculations -- Informal Discussion*

Location: 3110 ESB, 10:00 am
Presenter(s): Dr. John E. Pask, Lawrence Livermore National Laboratory, University of California, Livermore, CA
Contact: Jeongnim Kim

Wednesday, December 1, 2004 Finite-Element Method for Large-Scale Ab Initio Electronic-Structure Calculations*

Location: 5307 Beckman Institute, 2:00 pm
Presenter(s): Dr. John E. Pask, Lawrence Livermore National Laboratory, University of California, Livermore, CA
Contact: Jeongnim Kim
Description: Over the course of the past two decades, density functional theory (DFT) has proven to be an accurate and reliable basis for the understanding and prediction of a wide variety of materials properties from first principles (ab initio). However, the solution of the equations of DFT remains a formidable task and this has limited the range of materials problems which can be investigated by such means. In this talk, I discuss work on a new finite-element based method for large-scale ab initio electronic-structure calculations, with the goal of extending the range of materials systems that can be investigated by such rigorous, quantum mechanical means. The finite-element method is a general approach for the solution of partial differential and integral equations. Like the traditional planewave method which uses a Fourier basis, the finite-element method is a systematically improvable, variational expansion approach. Unlike the planewave method, however, its basis functions are strictly local in real space; and it is from this that the flexibility and scalability of the method derives. We discuss our work on a general finite-element based electronic-structure method, allowing Bloch-periodic, Dirichlet, and Neumann boundary conditions, or any mixture thereof, arbitrary unit cells, and arbitrary sampling of the Brillouin zone. We present applications of the method to non-self-consistent ab initio positron distribution and lifetime calculations for systems of over 5000 atoms, as well as initial self-consistent results.

Wednesday, September 15, 2004 Formulation of the Anisotropic Coarsening Theory (ACT) and applications to the liquid phase sintering of silicon nitride*

Location: 3-110 ESB, 2:30 pm
Presenter(s): Nithaya Chetty University of KwaZulu-Natal, South Africa
Contact: R. M. Martin
Description: We have developed a new coarsening theory that more completely describes grain growth of a system of anisotropic particles by Ostwald ripening compared with the conventional LSW theory. Our model is applied to the coarsening of beta-silicon nitride in a liquid medium, where the anisotropy is due to the properties of the different surfaces of the hexagonal particles. Our model suggests the possiblity of different grain growth mechanisms on the different surfaces that might explain the controversies in the literature on the measurement of the growth exponents of these systems. Numerical experiments are performed to study the evolution of the particle number distribution function under experimental conditions such as diffusion-limited and reaction-limited growth.

Thursday, August 19, 2004 Coupled Electron-Ion Monte Carlo Method and Application to Metallic Hydrogen*

Location: 3-110 ESB, 3:00 pm
Presenter(s): Carlo Pierleoni, Physics Dept., University of L'Aquila, Italy
Contact: David Ceperley
Description: I describe a new Quantum Monte Carlo (QMC) methodology, which couples Path Integral Monte Carlo (PIMC) for finite temperature protons with Quantum Monte Carlo methods for ground state electrons, and I apply it to metallic hydrogen for pressures beyond the molecular dissociation threshold. At variance with previous QMC methods (Restricted-PIMC and Diffusion-QMC) which treat protons and electrons at the same level, our present one is based on the Born-Oppenheimer separation of time scales. This new method, called Coupled Electron-Ion Monte Carlo (CEIMC)[1], is able to fill most of the gap between the Restricted-PIMC and the Diffusion-QMC for metallic hydrogen. Key ingredients of CEIMC for metallic hydrogen are: 1) the use of a recently derived analytic form for the electronic trial wave function including three-body and backflow effects [2]; 2) the implementation of an efficient Reptation QMC algorithm to sample the electronic ground state within the Fixed node approximation; 3) the average of the electronic properties over twisted boundaries to minimize the finite size effects; 4) the use a suitable Trotter breakup of the proton density matrix which minimize the number of protonic time slices in the PIMC.

I will present results for metallic hydrogen in a range of densities and temperatures where molecules are absent and where protons undergo a solid-fluid transition. We report results for the EOS and give a qualitative location of the transition line[3].

In comparison with previous Car-Parrinello Molecular Dynamics (CPMD) results[4], our data exhibit more structure and higher melting temperature of the proton crystal.

[1] D. M. Ceperley, M. Dewing and C. Pierleoni. Lecture Notes in Physics extitBridging Time Scales, Vol 605, pg. 473-499. ed. P. Nielaba et al., Springer-Verlag (2003). (physics/0207006).
[2] M. Holzmann, D.~M. Ceperley, C. Pierleoni and K. Esler, Phys. Rev E extbf68, 046707 (2003).
[3] C. Pierleoni, D.M. Ceperley and M. Holzmann extitCoupled Electron Ion Monte Carlo Calculations of Dense Metallic Hydrogen, Phys. Rev. Lett. accepted (Aug 2004), (physics/0405056).
[4] J.Kohanoff and J.P.Hansen, Phys. Rev. Lett. extbf74, 626 (1995), Phys. Rev. E extbf54, 768 (1996)

Thursday, August 12, 2004 Electronic structure by Slater determinant random walks*

Location: 3-110 ESB, 3:00 pm
Presenter(s): Prof. Shiwei Zhang,Department of Physics College of William and Mary
Contact: David Ceperley, ceperley at uiuc.edu

Monday, April 12, 2004 Critical dynamics in a funnel-shaped landscape: a Landau-type theory of the glass transition*

Location: Room 280 MRL, 12:00 pm
Presenter(s): Professor Bulbul Chakraborty, Brandeis University
Contact: Prof. Paul Goldbart (Physics) or Duane Johnson (MatSE)
Abstract: Glassy dynamics occur in a large variety of systems, such as supercooled liquids, foams and granular matter. They are characterized by an exponentially rapid increase of relaxation times, as a control parameter such as temperature or density in tuned, and by a non-exponential decay of time-dependent correlation functions indicating a broad distribution of timescales. In this talk, I will present an exact solution of a Landau model of an order-disorder transition with activated critical dynamics. The model describes a funnel-shaped topography of the order parameter space in which the number of energy lowering trajectories rapidly diminishes as the ordered ground state is approached. This leads to an asymmetry in the effective transition rates, which results in a non-exponentia lrelaxation of the order-parameter fluctuations and a Vogel-Fulcher-Tammann divergence of the relaxation times,typical of a glass transition. I will discuss a lattice model where this class of critical dynamics is realized and I will argue that the Landau model provides a general framework for studying glassy dynamics in a variety of systems.

Thursday, February 12, 2004 Fast Eigenvalue/Eigenvector Computation for Dense Symmetric Matrices

Location

Room 1003 MRL, 11:00 am

Presenter(s)

Inderjit Dhillon

Contact

Eric De Sturler

Abstract

Computing the eigenvalues/eigenvectors of a dense symmetric matrix is a classical problem and usually proceeds in 3 phases: (i) reduce the matrix to tridiagonal form, (ii) solve the tridiagonal eigenproblem and (iii) back-transform to obtain eigenvectors of the original matrix. In this talk, we present the first O(n^2), numerically stable, embarrassingly parallel algorithm for phase (ii). All previous algorithms for this purpose were O(n^3) in complexity, and in practice, often accounted for 80% of the total time for solving large dense eigenproblems. The new algorithm achieves O(n^2) complexity by avoiding all Gram-Schmidt orthogonalization.

The crucial ingredients of the new algorithm are:

(1) using factored forms to achieve provably high relative accuracy,
(2) using "twisted factorizations" to compute approximate eigenvectors with probably small relative residual norms.
(3) using multiple factored forms to "separate" clustered eigenvalues, thereby automatically obtaining numerically orthogonal approximations to eigenvectors (no Gram-Schmidt). An interesting facet of our work is that high accuracy in intermediate computations leads to a much faster overall algorithm.

Impressive speedups are obtained on matrices from the real-life applications of computational quantum chemistry (PNNL) and finite-element modeling (from Jeff Bennighof). The largest dense problem solved "in-core" on a 256-node parallel computer is of size 128,000 x 128,000 which takes about 8 hours of CPU time. A preliminary version of the sequential software is now included in the LAPACK public-domain library.

The work on the sequential algorithm is joint with Beresford Parlett of UC Berkeley, while the parallel algorithm has been developed jointly with Paolo Bientinesi and Robert van de Geijn of UT Austin.

Tuesday, February 10, 2004 Modeling Elastic and Plastic Deformations in Materials Physics

Location: Room 280 MRL, 12:00 pm
Presenter(s): Ken Elder, Dept. of Physics, Oakland University
Contact: Nigel Goldenfeld
Abstract: The vast majority of naturally occurring or man-made solids are not in equilibrium and contain complex spatial structures on nanometer, micron or millimeter length scales. This is particularly important since these morphologies often determine the mechanical, electrical and optical properties of the material. Elastic and plastic deformations frequently have a significant impact on the nature of the morphologies, but are difficult to incorporate in theoretical treatments. In this talk I would like to discuss a simple method of modeling elastic and plastic deformations in non-equilibrium phenomena. For illustrative purposes a number of applications will be considered including liquid phase epitaxial growth, spinodal decomposition, eutectic solidification, dendritic growth and material hardness.

Monday, February 9, 2004 Control of Exchange Interaction in a Double Dot System*

Location

Room 280 MRL, 2:00 pm

Presenter(s)

M. Stopa, Tarucha Mesoscopic Correlation, Project, ERATO-JST, Atsugi, Japan

Contact

Jean-Pierre Leburton

Abstract

Electron spin in semiconductors has been shown to remain coherent over remarkably long times [1]. This is because direct coupling to the magnetic moment of an electron through, for example, hyperfine interaction or spin-orbit coupling is weak. This makes spin useful for quantum information processing in general and a good qubit candidate for quantum computing in particular [2]. The relative isolation of a spin from its environment, however, makes spinmanipulation and especially single spin measurement very challenging. The Pauli exclusion principle, however, causes the Coulomb interaction between electrons with parallel spins to be generally weaker than between electrons with anti-parallel spins. This exchange effect is the basis of entanglement interactions between spin qubits in quantum computing proposals [2].

In a double quantum dot with one electron on each dot, the anti-ferromagnetic exchange coupling J is equivalent to the splitting between the ground singlet and ground triplet states of the two electron system. In this work, we combine density functional (DF) calculations with exact diagonalization methods to compute the electronic structure of a lateral, GaAs-AlGaAs heterostructure based double quantum dot, thereby incorporating a realistic geometry with a correct treatment of correlation. We use the converged Kohn-Sham eigenstates for spinless electrons as a single particle basis and form all symmetric and anti-symmetric combinations of two-electron states. The Coulomb matrix elements between these states are determined via Poisson's equation which is very efficient in comparison with computation of six dimensional integrals and which automatically includes the effects of screening by the surface metal gates of the double dot. The one-particle energies are carefully corrected for double counting of the Coulomb interaction. Since our single particle basis is composed of states of the double dot, tunnelling need not be included as a perturbation.

The principle result which we emphasize here concerns the evolution of J and the exchange integral V_ex, with magnetic field. We show that V_ex, which arises from the overlap in the barrier between the two localized wave functions, is not monotonic with B. This results from the competition between the lateral (perpendicular to the line between the two dots) compression of the wave functions with B, which increases V_ex, and the contracting influence of B, which reduces the overlap in the barrier. We suggest how the inter-dot gating configuration might be varied, between, say, a long narrow channel and a short wide one to modulate the exchange interaction and its dependence on magnetic field, and also on inter-dot barrier height and dot potential offset.

[1] T. Fujisawa et al., Science 282, 932 (1998)
[2] G. Burkard et al., Phys. Rev. B, 59, 2070 (1999).

Friday, January 16, 2004 An informal discussion: *What is nano?**

Location: Room 280 MRL, 2:00 pm
Presenter(s): Vincent Crespi, Professor of Physics and Materials Science and Engineering, Penn State University
Contact: Richard Martin

Monday, December 8, 2003 Structural Topology Optimization and Applications*

Location: 151 Loomis Laboratory, 4:00 pm
Presenter(s): Emilio C. N. Silva, University of Sao Paulo, Brazil
Contact: H. Paulino Glaucio
Abstract: Topology optimization is a general structural optimization method that combines optimization algorithms with the finite element method. The main applications considered in this presentation are piezoelectric devices which consist of a flexible structure (compliant mechanism) actuated by one or more piezoceramics. The flexible structure must generate different output displacements and forces in different specified points of the domain and directions, for different excited piezoceramics. It acts as a mechanical transform by amplifying and changing the direction of the piezoceramics output displacements. These devices can have a wide range of applications in precision mechanics such as machine tools, lens focus system of photograph machines, microsurgery tools, nanotechnology equipment, cell manipulators, lens positioner for interferometers. microelectromechanical systems (MEMS), etc. By changing the topology of these devices or their components an improvement in their performance characteristics can be obtained. Thus, in this work the potentiality of applying synthesis methods to design these piezoelectric devices is shown using topology optimization. Among the devices it will be presented the design of flextensional actuators, linear piezoelectric motors and multi-flexible micro-manipulators. The examples presented show that the synthesis method is indeed a promising tool to design these devices, showing that their application is still in the beginning and there is much room for further improvements.

Monday, November 10, 2003 Critical thickness for ferroelectricity in barium titanate ultrathin films*

Location: Room 3-110 ESB, 2:00 pm
Presenter(s): Javier Junquera, Department of Physics and Astronomy, Rutgers University
Contact: Richard Martin
Abstract: ABO₃ ferroelectric perovskites are promising candidate materials for Non-volatile Ferroelectric Random Acces Memories (FeRAM). Industry's demand for ultrahigh density information storage imposes the reduction of the cell- sizes and thicknesses of the ferroelectric while some size effect should be expected on the ferroelectricity of the system. Previous first-principles based effectivehamiltonian calculations 1 and full firstt-principles simulations 2 predicted ferroelectric ground states for ABO₃ ultrathin films under zero field boundary conditions and suggested the absence of a critical size. However, in these previous approaches, the role played by the metallic electrodes on the structure and polarization of the system was not explicitely treated but only implicitely included through particular electric and mechanical boundary conditions. Here, we report density-functional first-principles calculations ₃ on a realistic SrRuO₃/BaTiO₃/SrRuO₃ ferroelectric capacitor structure under short-circuit boundary conditions. A critical thickness for ferroelectricity is identified and valued at 24 A (six unit cells of BaTiO₃). A depolarizing electrostatic field. caused by the existence of finite dipoles at the metal/ferroelectric interfaces is responsible for the disapearance of the ferroelectricity. Above the critical thickness, we recover a polarized ground-state, although with a reduced spontaneous polarization with respect to the bulk, in good agreement with experimental results 4. A simple model, based only on the electrostatic of the system, is proposed to explain the evolution of the ferroelectric properties with the film thickness. Our results suggest a lower limit for useful thicknesses of ferroelectric materials in electronic devices.

Friday, November 7, 2003 Computational challenges and solution algorithms in electronic structure calculations*

Location: Room 280 MRL, 10:00 am
Presenter(s): Prof. Yousef Saad, Department of Computer Science and Engineering, University of Minnesota
Contact: Duane Johnson
Abstract: Density Functional Theory (DFT) is a successful technique used to determine the electronic structure of matter which is based on a number of approximations. It converts the original n-particle problem into an effective one-electron system, resulting in a coupled one-electron Schrodinger equation and a Poisson's equation. This coupling is nonlinear and rather co mplex. It involves a charge density rhohich can be computed from the wavefunctions psi, for all occupied states. This gives rise to what may viewed as a non-linear eigenvalue problem which is solved iteratively. The challenge comes from the large number of eigenfunctions to be computed for realistic systems with, say, hundreds or thousands of atoms. We will begin by discussing a parallel implementation of a finite difference approach for this problem and report on some results. We will also explore the fundamental underlying linear algebra which can be viewed as a problem of determining the diagonal of a projector associated with an invariant subspace. Methods that avoid completely the computation of eigenvectors will be briefly discussed. Finally, we will present current work on time-dependent density functional theory with an emphasis on showing some of the resulting big challenges in matrix computations encountered in this application.

Friday, November 7, 2003 Atoms on the Move: Simulating the Properties of Semiconductor Liquids*

Location: Room 280 MRL, 11:00 am
Presenter(s): Prof. James R. Chelikowsky, Institute for the Theory of Advanced Materials in Information Technology Digital Technology Center and Department of Chemical Engineering and Materials Science, University of Minnesota
Contact: Duane Johnson
Abstract: Liquids present special chal lenges in predicting their electronic and structural properties. They contain numerous degrees of freedom and no symmetry. In addition, one can only discuss their properties in terms of statistical averages. I will discuss applications of electronic structure methods using ab initio molecular dynamics to a number of semiconductor liquids. Our simulations are based on quantum forces extracted from a solution of the electronic structure problem at each time step of the simulation. I will illustrat e this method by simulating elemental liquids like Si and Ge, in addition to a number of III-V, II-VI and IV-VI semiconductor liquids such as GaAs, CdTe, and GeTe.

Wednesday, October 29, 2003 Electronic transport in Nanostructures from first principles: a simulation tool*

Presenter(s): Dr. Pablo Ordejon, Institut de Ciència de Materials de Barcelona
Contact: Richard Martin
Abstract: Nanoelectronics is one of the hottest topics in current materials science research. I will describe recent efforts in developing fast and accurate simulation tools for electronic transport in devices at the nanoscale. In particular, I will present a first-principles method, based on Density Functional Theory, for calculating the electronic structure, electronic transport, and forces acting on the atoms, for atomic scale systems connected to semi-infinite electrodes and with an applied voltage bias. The method has been applied to several systems, including nanometer-scale metallic wires, organic molecules and carbon nanotubes.

Friday, October 24, 2003 Deriving Plasticity: Attempts at a Theory for Dislocation Patterning and Work Hardening*

Location: Room 3-110 ESB, 11:00 am
Presenter(s): Jim Sethna, Department of Physics, Cornell University
Contact: Karin Dahmen
Abstract: When you abuse your fork in cutting a tough piece of meat, and it bends irreversibly, plastic deformation has occured. Plastic deformation in crystals arises because of the creation, motion, and tangling of myriads of dislocation lines, forming complex patterns and cellular structures. We're trying to develop a mesoscale field theory for rate-independent plasticity, governing behavior on scales large compared to the dislocations and explaining the emergence of these cellular structures. Largely using symmetry arguments, we've developed a scalar theory that exhibits a yield stress, work hardening, and cell boundary formation. We're now developing a more realistic theory based on the dislocation density tensor. In collaboration with Markus Rauscher, Jean-Phillipe Bouchaud, and Surachate Limkumnerd.

Friday, September 12, 2003 Full Multiple Spawning with QM/MM Methods for Excited States: Direct Photodynamics for Large Chromophores in Proteins and Condensed Phases*

Location: Room 280 MRL, 11:00 am
Presenter(s): Alessandro Toniolo, Dipartimento di Chimica e Chimica Industriale, Universita di Pisa
Contact: Todd Martinez
Abstract: First principles simulations of photodynamics have recently been demonstrated using the ab initio multiple spawning (AIMS) method. The AIMS method uses a multireference wave function ansatz in order to achieve a globally accurate description of the ground and excited state potential energy surfaces and their nonadiabatic couplings. AIMS has been applied to molecules with up to 26 atoms; however, the extreme computational expense poses a serious obstacle to studies of large molecules and complex environments. We use a floating occupation molecular orbital (FOMO)semiempirical configuration interaction (CI) method which ameliorates these difficulties and demonstrate its utility for photoactive protein dynamics. The FOMO-CASCI method has been incorporated in MOPAC, including the possibility of a hybrid quantum mechanical/molecular mechanical (QM/MM) description. Using the QM/MM decomposition, we describe the active part of the system (e.g. achromophore and possibly a small part of the environment) with the FOMO-CASCI method, and the remainder of the system is modeled with a classical force field method. The QM and MM sub-regions are joined by using specific connection atoms. Furthermore, the FOMO-CASCI-QM/MM method has been implemented with direct nonadiabatic dynamics techniques, including both surface hopping and multiple spawning. The new FOMO-CASCI-QM/MM method is applied to the photodynamics of the Green Fluorescent Protein fluorophore in vacuum, aqueous, and protein environments. The results allow us to understand why the fluorophore exhibits its peculiar fluorescence only when embedded in the protein environment.

Friday, August 29, 2003 Simulating the phase behaviour of polydisperse fluids*

Location: Room 280 MRL, 11:00 am
Presenter(s): Nigel Wilding, University of Bath, U.K.
Contact: Erik Luitjen
Abstract: Many complex fluids comprise mixtures of similar rather than identical constituents. Examples are colloidal dispersions in which the particles may exhibit a spread of sizes, shapes or surface charges, and polymers which may have a range of chain lengths. This dependence of particle properties on one or more continuous parameters is termed polydispersity. In this talk I will outline some of the interesting effects polydispersity can have on bulk phase behaviour. I will then focus attention on the computational challenges posed by polydispersity and describe new general simulation algorithms that allow polydisperse fluids to be tackled effectively within a grand or semi-grand canonical ensemble Monte Carlo framework. Simulations results will then be presented for the equation of state of size-disperse hard spheres and the liquid-gas phase behaviour of a size-disperse Lennard-Jones fluid. Finally I will compare my results with new and existing theoretical predictions and show that the proper inclusion of packing effects in theories is crucial for the correct reproduction.

Wednesday, July 2, 2003 New small silicon interstitial clusters*

Location: Room 280 MRL, 2:00 pm
Presenter(s): Kaden Hazzard, Department of Physics, The Ohio State University, http://www.physics.ohio-state.edu/hazzard
Contact: Jeongnim Kim
Abstract: Silicon self-interstitial clusters dramatically enhance boron's diffusion, which is important in the fabrication of silicon devices. By combining long-time, tight-binding molecular dynamics simulations with novel multi-resolution analysis techniques, we predict new stable structures of these silicon interstitial clusters. A new tri-interstitial ground state is discovered, highlighting this approach. Its energy within density-functional theory (DFT) is 400 meV below the previously assumed ground state. Interestingly, this structure provides a link between compact interstitial clusters and experimentally observed extended, planar defects. Two new di-interstitials, two new tri-interstitials, and single-interstitials bound to distorted di-interstitials are also detected from the dynamics and examined with DFT. We augment our understanding of the dynamics uncovered from molecular dynamics with nudged-elastic band and dimer method saddle-point searches. This provides a complete picture of the dynamics of small-interstitial clusters. In particular, the di-interstitial and tri-interstitial are both extremely mobile. However, the new tri-interstitial ground state is quite stable and intermittently stops this rapid diffusion.

Wednesday, June 18, 2003 Theory of the tunneling spectroscopy in buried metallic nanoparticles*

Location: Room 280 MRL, 2:00 pm
Presenter(s): Gustavo A. Narvaez, Department of Physics, The Ohio State University, http://www.physics.ohio-state.edu/gustavo/
Contact: Jeongnim Kim
Abstract: Single quantum level tunneling spectroscopy is a powerful tool to probe the electronic structure of individual metallic nanoparticles. The observed spectra show resonances whose spacing and magnitude depend sensitively on the bias voltage. A microscopic theory for the electron tunneling through buried metallic nanoparticles naturally explains the spacing, and the relative magnitude under bias reversal. This theory begins with a microscopic model for the electronic structure of the nanoparticle and calculates the tunneling spectra using a master equation formalism. Two fundamental aspects combine to predict the observed features: (i) The nonuniform spacing of the electronic levels arising from disorder-induced fluctuations of the electronic wavefunctions, and (ii) the Coulomb blockade energy being large compared to the average level spacing. The theory also predicts that (a) the slopes of the resonances with respect to gate voltage are affected by the local electrostatic environment. The mean slope grows larger for smaller nanoislands and can be twice that predicted for large particles. Measuring these slopes is a direct probe of the magnitude of nanoscale effects. (b) If the intragrain electronic relaxation and bottleneck tunneling time are such as to admit a significant population of non-equilibrium states the density of tunneling resonances may be much greater than observed to date.

Wednesday, May 1, 2002 Fracture patterns and kinetics in deposition of solids*

Location: Room 280 MRL, 2:30 pm
Presenter(s): Boris Yakobson, Rice University
Contact: MCC & Young Huang (ME)
Description
Abstract: Chemical transformation of solids is often complicated by the intricate multiple fragmentation, which is caused by emerging internal mismatch. New surfaces and channels created by such fracture facilitate in turn the chemical transport of the volatile component. For a long time no self-consistent approach to this coupled kinetics-mechanics problem existed. We will present analysis that begins from single crack equilibrium, and through minimization of the free energy describes the ensemble of cracks. This enables one to solve the "selection problem" for the pattern-formation process and to obtain simple equations for the rate of crack network propagation.

Monday, March 25, 2002 Tight-Binding for Real Materials*

Location: Room 280 MRL, 11:00 am
Presenter(s): Mike Mehl, Naval Research Laboratory
Contact: Duane Johnson
Description: Accurate first-principles quantum mechanical calculations for real materials are computationally limited to no more than 100-1000 atoms. At larger scales, atomistic potentials such as the Embedded Atom Method are used, but these methods may miss important physics driven by changes in the electronic structure, e.g., at cracks and defects. Parametrized tight-binding (TB) methods exist between these two extremes. Unlike atomistic potentials, the quantum mechanical behavior of the electrons is maintained, but the computational effort is much less than needed for comparably sized first-principles calculations. This talk describes the NRL Tight-Binding Method (NRL-TB), which maps the results of a limited set of first-principles calculations to a two-center non-orthogonal Slater-Koster TB Hamiltonian. The on-site Hamiltonian parameters are sensitive to the local environment and the hopping parameters are bond-length dependent. The method has been shown to successfully determine elastic constants, phonon frequencies, vacancy formation energies, and surface energies. In addition, TB molecular dynamics simulations are used to study thermal expansion and atomic diffusion. We will discuss applications to spin-polarized systems, non-collinear magnetization, and multi-component systems, including MgB₂.

Wednesday, February 27, 2002 Thermal Activation of Dislocation Motion*

Location: Room 280 MRL, 11:00 am
Presenter(s): Frank Nabarro, Dept. of Physics, University of the Witwatersrand, South Africa
Contact: Carl Altstetter
Description: This talk will explore new developments in the classical theory of thermal activation of dislocations during plastic deformation of metals. In simplest terms, the talk addresses the question of how a dislocation surmounts the Peierls-Nabarro barrier. The expression for the activated motion of dislocations under shear stress is re-examined at high stresses, taking into account non-linear elastic effects in the activated state. Activation of dislocations at low stresses and the implications for the activation volume is also explored. Following stress-assisted thermal activation of the dislocation, the load is redistributed to other sub-critical activation sites, producing a multiplication factor which is stress-dependent and changes the relationship between strain rate and applied stress.

Tuesday, February 26, 2002 Electronic Structure Codes and Methods Development at NERSC*

Location: Room 280 MRL, 3:00 pm
Presenter(s): Andrew Canning, NERSC/Lawrence Berkley Laboratory
Contact: Jeongnim Kim
Description: NERSC (The National Energy Research Scientific Computing Center) is an unclassified national computer facility run for the DOE by the University of California. NERSC has a 3000 processor IBM SP and a 692 processor Cray T3E. After a brief introduction to NERSC I will describe some NERSC activities in materials science code development such as PARATEC a parallel plane-wave DFT code and P-FLAPW a parallel FLAPW code that can simulate transition metal systems containing hundreds of atoms. The parallelization and scaling issues in these codes will be discussed.

Friday, October 12, 2001 Real-space multiscale methods in DFT*

Location

Room 280 MRL, 2:00 pm

Presenter(s)

Thomas Beck, Department of Chemistry, University of Cincinnati

Contact

Duane Johnson

Abstract

This talk will discuss progress in efficient solvers which have as their foundation a representation in real space, either through finite-difference or finite-element formulations. The relationship of real-space approaches to linear-scaling electrostatics and electronic structure methods is first discussed. Then the basic aspects of real-space representations are presented.

Multigrid techniques for solving the discretized problems are covered; these numerical schemes allow for highly efficient solution of the grid-based equations. Applications to problems in electrostatics are discussed, in particular numerical solutions of Poisson and Poisson-Boltzmann equations. Next, methods for solving self-consistent eigenvalue problems in real space are presented; these techniques have been extensively applied to solutions of the Hartree-Fock and Kohn-Sham equations of electronic structure, and to eigenvalue problems arising in semiconductor and polymer physics. Finally, real-space methods have found recent application in computations of optical response and excited states in time-dependent density functional theory, and these computational developments are summarized.

Multiscale solvers are competitive with the most efficient available plane-wave techniques in terms of the number of self-consistency steps required to reach the ground state, and they require less work in each self-consistency update on a uniform grid. Besides excellent efficiencies, the decided advantages of the real-space multiscale approach are: 1) the near-locality of each function update, 2) the ability to handle global eigenfunction constraints and potential updates on coarse levels, and 3) the ability the incorporate adaptive local mesh refinements without loss of optimal multigrid efficiencies.

Monday, November 6, 2000 Cluster growth from a reversible model of diffusion*

Location

Room 280 MRL, 2:00 pm

Presenter(s)

Raissa D'Souza, Bell Laboratories, Murray Hill, NJ

Contact

Karin Dahmen

Abstract

I will discuss a lattice gas model of cluster growth via the diffusive aggregation of particles in a closed system obeying a local, deterministic, microscopically reversible dynamics. This model roughly corresponds to placing the irreversible Diffusion Limited Aggregation model (DLA) in contact with a heat bath. Particles release latent heat when aggregating, while singly connected cluster members can absorb heat and evaporate. The heat bath is initially empty, hence we observe the flow of entropy from the aggregating gas of particles into the heat bath, which is being populated by diffusing heat tokens. Before the population of the heat bath stabilizes, the cluster morphology (quantified by the fractal dimension) is similar to a standard DLA cluster. The cluster then gradually anneals, becoming more tenuous, until reaching configurational equilibrium when the cluster morphology resembles a quenched branched random polymer.

The details of the model will be presented along with an analytic formulation for the macroscopic limit of the model. The subsequent discussion will focus on the transitions in the resulting growth morphology of the clusters and the approach to thermodynamic equilibrium, including prospects for controlling the resulting growth morphology.

Tuesday, September 5, 2000 Van der Waals interacton between atomic cluster of simple metal and metal surface*

Location: Room 280 MRL, 2:00 pm
Presenter(s): Prof. P. V. Panat, Department of Physics, University of Pune, India
Contact: MCC
Abstract: Sandogdher et. al. made a first direct quantitative test of van der Waals interaction between sodium atom and two parallel metal plates separated by about one micron. We make detailed theoretical calculation by modeling this interaction as a self-energy of the atom by virtual emission and re-absorption of surface plasmons of the metal surface. Realizing the success of this model, we calculated the interaction energy between magic number metal cluster and the metal surface. It is shown that interaction energy DE goes as 1/z³and constant of proportionality is a function of w_p and E_F/N^1/3, where w_pis the plasma frequency of the metallic surface, E_Fis the Fermi energy of the metallic cluster and N is the number of atoms in the cluster. Force of attraction between the cluster and the surface as a function of distance is calculated.

Wednesday, August 16, 2000 Universality in two-dimensional quantum magnets*

Location: Room 280 MRL, 2:00 pm
Presenter(s): Matthias Troyer, ITP, Dept. of Physics, ETH-Zurich, Switzerland
Contact: Richard Martin, Tadashi Ogitsu
Abstract: The quantum Monte Carlo loop algorithm has led to a breakthrough in the numeric simulation of quantum magnets. It enables us to perform simulations on lattices with up to millions of quantum spins. This has made possible the accurate investigation of the low temperature universal scaling regime in quantum magnets and the properties of quantum phase transitions. I will give an overview of theoretical and numerical work for the phase diagram of two-dimensional quantum Heisenberg antiferromagnets, emphasizing quantum phase transitions and crossovers as well as applications to quantum magnets and quantum Hall bilayer systems. In contrast to classical phase transitions in the vicinity of quantum phase transitions not only the critical exponents but also critical amplitudes and critical temperatures can be universal.

Tuesday, August 15, 2000 Generic parallel algorithms for lattice models*

Location: Room 2269 Beckman Institute, 2:00 pm
Presenter(s): Matthias Troyer, ITP, Dept. of Physics, ETH-Zurich, Switzerland
Contact: Richard Martin, Tadashi Ogitsu
Abstract: In this talk I will give an overview over the PALM++ project (Parallel Algorithms for Lattice Models). Using object oriented and generic programming techniques in C++ we are now able to do what was thought to be impossible before: developing general implementations of the standard algorithms (classical and quantum Monte Carlo with local and cluster updates, exact diagonalization, series expansion, density matrix renormalization group, classical and quantum transfer matrix methods) that work for a large variety of models and lattices while being as efficient as FORTRAN 77 programs. Object oriented programming techniques allow a very flexible implementation of the application framework and the automatic and transparent parallelization of algorithms like Monte Carlo simulations or series expansions. The run-time polymorphism implied by object orientation adds a performance penalty that is negligible at the framework level. In the inner loops of any actual simulation however the performance penalty exacted by run-time polymorphism is inacceptable. Generic programming is a modern programming technique which solves this problem by shifting the specialization to the specific model to compile-time. Using compile-time polymorphism it is possible for the compiler to optimize the generic algorithm to the spcific model and thus to obtain codes as efficient as a hand-optimized FORTRAN 77 implementation for a specific model. This will make it possible to perform high performance simulations of quantum many body problems without any serious programming - nearly as easy as using Mathematica. E.g. an application of a many body Hamiltionian $[sum_i -t(c^dag_ic_i+1+H.c.) -mu n_i + U n_i(n_i-1)]psi angle$ can now be coded as simple as: t sum(i,(-t*(cdag(i)*c(i+1)+HC)-mu*n(i)+U*n(i)*(n(i)-1))*psi) This has the potential to revolutionize the way computational methods are used in statistical and condensed matter physics.

Monday, June 26, 2000 Time Dependant Density-Functional Theory and Si clusters.*

Location: Room 4169 Beckman Institute, 2:30 pm
Presenter(s): Keith Glassford
Contact: Richard Martin
Abstract: Keith will present some of the new applications MSI has developed for the PC.

Wednesday, June 21, 2000 Time Dependent Density-Functional Theory and Si clusters.*

Location: Room 280 MRL
Presenter(s): Igor Vassiliev
Contact: Richard Martin
Abstract: Igor, a new MCC post-doc, will present some results of TDFT applied to Si clusters.

Tuesday, May 30, 2000 Stability of Si-interstitial complexes: from point to extended defects*

Location: Room 280 MRL
Presenter(s): Jeongnim Kim, Department of Physics, Ohio State University
Contact: Richard Martin
Abstract: Transient enhanced diffusion (TED) in boron-implanted silicon is the limiting factor in controlling dopant profiles for submicron Si-based devices. Interstitial defects in bulk Si generated during implantation have been identified as the sources for boron TED. A class of macroscopical interstitial defects, namely 311 defects, was suggested to emit interstitials that can contribute to the enhancement of boron diffusion under typical implantation conditions. We study the stability and electronic structure of interstitial clusters and interstitial chains by performing tight-binding and first-principle total energy calculations. Accurate parameterization of the defect-formation energy on the number of interstitials and interstitial chains, together with the anisotropy of the interstitial capture radius, enables macroscopic defect-growth simulations.

Monday, March 13, 2000 Parallel supercomputing in science and engineering*

Location

Room 112 Chemistry Annex

Presenter(s)

Ole Nielsen, Center for Atomic-scale Physics (CAMP), Technical University of Denmark

Contact

MCC

Abstract

Computer simulations of complex problems using high-performance computers have evolved to the point where the simulations enable important progress in many areas of science and engineering. The staggering developments in microprocessor technology have impacted also high-performance computing in the last decade. Custom-built vector-processors, which used to be the workhorses of computer centers, have almost everywhere been superseded by parallel microprocessor-based computers.

Today's parallel supercomputers are actually also custom-built because they require high-performance memory subsystems and data-communication networks. They are highly efficient for many types of simulation problems, provided that appropriate parallel algorithms are developed.

An important new trend is the construction of supercomputers by means of lots of mass-produced PCs or workstations. This is known as the "Beowulf" cluster concept. By combining commodity equipment into real parallel supercomputers, many classes of demanding supercomputing problems can be solved extremely cost-effectively.

This talk discusses a number of the technologies that go into building "commodity" supercomputers, both in terms of the computer and networking hardware, and in terms of the software. The role of proprietary software as well as Open Source software freely available on the Internet will be discussed.

An example application utilizing such a supercomputer is the Density-functional electronic structure code developed at CAMP, which among other things employs a new parallel eigensolver algorithm.

Outlooks for parallel supercomputing in the future conclude the talk.

Wednesday, February 23, 2000 Theory of composite-band Wannier states and order-N electronic-structure calculations

Location

Room 280 MRL

Presenter(s)

Takeo Hoshi, Dept. of Applied Physics, University of Tokyo

Contact

Richard Martin

Abstract

Wannier states (WS's) are re-investigated recently in the context of the order-N method, because their locality is essential to the order-N ansatz. A pioneering work by Kohn ('59) shows that, in a one-dimensional single-band case, the tail of WS wavefunctions decays exponentially with a decay parameter proportional to the square root of the bandgap. In three-dimensional composite-band cases, however, their general feature of the locality has not been well investigated.

This talk is devoted to our study of the locality of composite-band WS's; (i) We construct the 'exact' WS's of the valence and conduction band for the diamond-structure solids within tight-binding hamiltonians and analyze their locality by the conventional perturbation theory. (ii) From the localized-orbital order-N formulation, we directly derive the equation for the composite-band WS's, and also derive their localized property, as a general theory.

The results imply that the locality of WS's can be insensitive to the bandgap, which is quite different from that in the single-band case. Ref. cond-mat/9910424

Wednesday, February 23, 2000 Molecule-surface Interactions by Design

Location: Room 112 Chemistry Annex, 4:00 pm
Presenter(s): Andrew Rappe
Contact: MCC
Abstract: The focus of our research is the theoretical modeling of chemical structure and reactivity from first principles. We are interested in performing research which enhances our ability to predict chemistry theoretically and which sheds light on complex systems of interest. To accomplish this, we solve the equations of quantum mechanics on state-of-the-art computers. Comparison of these theoretical predictions with experimental observations provides a stringent test of both our theoretical understanding of the system and the interpretation of the experiment. In addition, we can study systems which are difficult to create or to analyze experimentally. This can provide insight into an entire class of systems, and it can highlight systems which may be fruitful to investigate experimentally.

MCC Visitors

Tuesday-Thursday, February 5-7, 2008 Alan Aspuru-Guzik, Harvard University*

Contact: Amy Young
Description: Professor Aspuru-Guzik will give a talk about a new research direction: quantum coherence and energy transfer. He will also meet with faculty and students in chemistry, physics, and engineering during his visit.

Monday-Friday, September 24-28, 2007 Weidong Sheng, National Research Council, Ottawa, Canada*

Contact: J. P. Leburton, jleburto --> uiuc.edu
Description: Dr. Sheng will give a seminar and meet with quantum dot researchers.

Wednesday-Saturday, August 15 - December 15, 2007 Sashi Satpathy, University of Missouri*

Contact: Richard Martin, Local Organizer
Description: This visit provides a way for the Center to be involved in research on correlated electrons in oxides. Othe research interests of this visitor include spintronic materials and photonics. Professor Satpathy will bring 4 postdocs.

Wednesday-Saturday, January 24-27, 2007 Prof. Amy Langville, College of Charleston, South Carolina, Department of Mathematics*

Organization: College of Charleston, South Carolina
Contact: Amy Young, 217-333-0512
Description: Professor Langville will give two talks: ’Google’s PageRank and Beyond: The Science of Search Engine Rankings’ and ’Algorithms behind search engines’. This visit is sponsored by the Materials Computation Center and Women in Computer Science, UIUC.

Wednesday-Friday, November 1-3, 2006 Dr. Nicola Spaldin, University of California, Santa Barbara, Materials Department *

Contact: Amy Young, amyoung --> uiuc.edu
Description: Dr. Spaldin is a member of the MCC’s Advisory Board, and will attend the annual board meeting and meet with researchers and students one morning.

Wednesday-Friday, November 1-3, 2006 Dr. Warren Pickett, University of California Davis, Department of Physics *

Contact: Amy Young, amyoung --> uiuc.edu
Description: Dr. Pickett is a member of the MCC’s Advisory Board, and will attend the annual board meeting and meet with researchers and students one morning.

Tuesday-Saturday, October 31 - November 4, 2006 Dr. Glenn Martyna, IBM TJ Watson Laboratory, Yorktown Heights, New York *

Contact: Joyce Lucas, joyce --> ks.uiuc.edu
Description: Dr. Martyna is a member of the MCC’s Advisory Board, and will attend the annual board meeting and give a talk about his current research.

Sunday-Tuesday, September 17-19, 2006 Andreas Berge, Hitachi Global Storage Technologies, San Jose, CA*

Contact: K. Dahmen
Notes: Tentative - dates may change slightly

Monday-Friday, September 11-15, 2006 Sandro Sorella, SISSA/ISAS, Trieste Italy*

Contact: Michele Casula, casula --> express.cites.uiuc.edu
Description: During his visit, Dr. Sorella will meet with D. Ceperley, R. Martin, M. Casula and J. Kim and other members of MCC and quantum Monte Carlo methods, in particular for pseudopotentials, correlated wavefunctions and wavefunction optimization. He will give a talk on Sept 12 to MCC and Sept 15 in the Physics Dept.
Notes: This visit is jointly sponsored by the Physics Department and the MCC.

Saturday, August 5, 2006 Haydar Arlsan, Zonguldak Karaelmas Unviersity, Turkey*

Contact: Duane Johnson
Description: Dr. Arslan is a summer school participant and was invited to give a presentation. He prepared a short presentation on his research.

Saturday, August 5, 2006 Bothina Hamad, University of Jordan *

Contact: Duane Johnson
Description: Dr. Hamad is a summer school participant and was invited to give a presentation. This lecture "Education and research in Jordan, challenges and outlooks" will offer MCC staff and summer school participants a view of the research environment at her home institution.

Thursday, August 3, 2006 Huajun Fan, Prarie View A&M University*

Contact: Duane Johnson
Description: Dr. Fan is a summer school participant and was invited to give a presentation. This lecture "Nano-scale modeling with Undergraduates at Prairie View A&M University" will offer MCC staff and summer school participants a view of the research environment at his home institution.

Friday-Wednesday, June 2-7, 2006 Ivo Souza, UC Berkeley*

Contact: David Ceperley

Thursday-Saturday, April 6-8, 2006 Shiwei Zhang, Department of Physics College of William and Mary*

Contact: David Ceperley

Wednesday-Saturday, March 29 - April 8, 2006 Carlo Pierleoni, Physics Dept., University of L’Aquila, Italy*

Contact: David Ceperley

Thursday, March 9, 2006 Francois Willaime, Service de Recherches de Metallurgie Physique. CEA/Saclay*

Location: Room 280 MRL, 10:00 am
Contact: Pascal Bellon, bellon --> uiuc.edu

Monday, December 12, 2005 Roland Stumpf, Materials Physics, Sandia National Labs, Livermore, CA*

Contact: Duane Johnson, duanej --> uiuc.edu
Description: Dr. Stumpf will give a talk on reversible hydrogen storage during his stay.

Sunday-Tuesday, October 23-25, 2005 Dr. Patrick Rinke, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany*

Contact: Kris Delauney, kdelaney --> uiuc.edu
Description: Dr. Rinke will meet with faculty and students during his stay, and give a talk.

Monday-Tuesday, August 29-30, 2005 D.G. Austing, NRC, Ottawa, Canada *

Contact: J. P. Leburton, leburton --> uiuc.edu
Description: Dr. Austing is collaborting with Dr. Leburton on experimental and computational research on quantum dots. Dr. Austing will give a talk during his stay.

Monday-Thursday, April 18-28, 2005 Carlo Pierleoni, Physics Dept., University of L’Aquila, Italy*

Contact: David Ceperley

Sunday-Tuesday, December 5-7, 2004 Nobuhiko Akino, Sumitomo Chemical Co., Ltd.*

Contact: Richard Martin
Description: Dr. Akino will present a lecture about his research during his stay.

Wednesday, December 1, 2004 John E. Pask, Lawrence Livermore National Laboratory, University of California, Livermore, CA*

Contact: Jeongnim Kim
Description: Dr. Pask's visit is co-sponsored with PECM at NCSA.

Sunday-Friday, November 7-12, 2004 Lucia Reining, Laboratoire des Solides Irradis, Centre National de la Recherche*

Contact: Richard Martin and David Ceperley
Description: Dr. Reining will collaborate with R. Martin and D. Ceperely on a book on many-body theory and computation for condensed matter. She will give a seminar and special lectures on methods.

Tuesday-Monday, August 17-23, 2004 Carlo Pierleoni, Physics Dept., University of L'Aquila, Italy*

Contact: David Ceperley

Monday-Sunday, August 9-15, 2004 Prof. Shiwei Zhang, Department of Physics College of William and Mary*

Contact: David Ceperley, ceperley at uiuc.edu

Monday-Thursday, August 2-5, 2004 Frank Pinski, Univ. of Cincinnati*

Contact: Duane D. Johnson

Sunday-Saturday, August 1, 2004 - January 15, 2005 Nithaya Chetty, University of KwaZulu-Natal, South Africa*

Contact: Richard Martin

Sunday-Monday, April 11-12, 2004 Bulbul Chakraborty, Brandeis University*

Contact: Duane Johnson

Monday-Wednesday, March 8-10, 2004 Irene Burghardt, Chemistry Department, ENS Paris*

Contact: Todd Martinez

Wednesday-Friday, February 11-13, 2004 Inderjit Dhillon, Department of Computer Science, University of Texas at Austin*

Contact: Eric de Sturler

Monday, February 9, 2004 M. Stopa, Tarucha Mesoscopic Correlation, Project, ERATO-JST, Atsugi, Japan*

Contact: Richard Martin and Jean-Pierre LeBurton
Notes: 25

Friday, January 23, 2004 Vincent Crespi, Professor of Physics and Materials Science and Engineering, Penn State University*

Contact: Richard Martin
Notes: 2

Monday, December 8, 2003 Emilio C. N. Silva, University of Sao Paulo, Brazil*

Contact: H. Paulino Glaucio

Monday, November 10, 2003 Javier Junquera, Department of Physics and Astronomy, Rutgers University*

Contact: Richard Martin

Friday, November 7, 2003 Prof. Yousef Saad, Department of Computer Science and Engineering, University of Minnesota*

Contact: Duane Johnson

Friday, November 7, 2003 Prof. James R. Chelikowsky, Institute for the Theory of Advanced Materials in Information Technology Digital Technology Center and Department of Chemical Engineering and Materials Science, University of Minnesota*

Contact: Duane Johnson

Wednesday, October 29, 2003 Dr. Pablo Ordejon, Institut de Ciència de Materials de Barcelona*

Contact: Richard Martin

Friday, October 24, 2003 Jim Sethna, Department of Physics, Cornell University*

Contact: Karin Dahmen

Friday, September 12, 2003 Alessandro Toniolo, Dipartimento di Chimica e Chimica Industriale, Universita di Pisa*

Contact: Todd Martinez

Friday, August 29, 2003 Nigel Wilding, University of Bath, U.K.*

Contact: Erik Luitjen

Wednesday, July 2, 2003 Kaden Hazzard, Department of Physics, The Ohio State University, http://www.physics.ohio-state.edu/hazzard*

Contact: Jeongnim Kim

Wednesday, June 18, 2003 Gustavo A. Narvaez, Department of Physics, The Ohio State University, http://www.physics.ohio-state.edu/gustavo/*

Contact: Jeongnim Kim

Thursday-Friday, February 20-21, 2003 John Shumway*

Thursday, January 23, 2003 Jay A. Switzer*

Wednesday, May 1, 2002 Boris Yakobson, Rice University*

Contact: MCC & Young Huang (ME)
Description

Monday, March 25, 2002 Mike Mehl, Naval Research Laboratory*

Contact: Duane Johnson

Wednesday, February 27, 2002 Frank Nabarro, Dept. of Physics, University of the Witwatersrand, South Africa*

Contact: Carl Altstetter

Tuesday, February 26, 2002 Andrew Canning, NERSC/Lawrence Berkley Laboratory*

Contact: Jeongnim Kim

Monday, November 6, 2000 Raissa D'Souza, Bell Laboratories, Murray Hill, NJ*

Location: Room 280 MRL, 2:00 pm
Contact: Karin Dahmen

Tuesday, September 5, 2000 Prof. P. V. Panat, Department of Physics, University of Pune, India*

Contact: MCC

Tuesday-Wednesday, August 15-16, 2000 Matthias Troyer, ITP, Dept. of Physics, ETH-Zurich, Switzerland*

Contact: Richard Martin, Tadashi Ogitsu

Tuesday, May 30, 2000 Jeongnim Kim, Department of Physics, Ohio State University*

Contact: Richard Martin

Monday, March 13, 2000 Ole Nielsen,Center for Atomic-scale Physics (CAMP), Technical University of Denmark*

Contact: Richard Martin

Wednesday, February 23, 2000 Takeo Hoshi, Dept. of Applied Physics,University of Tokyo

Contact: Richard Martin

Wednesday, February 23, 2000 Andrew Rappe

Contact: MCC

Conferences, Workshops, and Summer Schools

Monday-Tuesday, July 21-22, 2008 Molecular Dynamics for Non-Adiabatic Processes

Description: Nanoscale phenomena, spanning multiple disciplines, share a unifying core problem: excitations away from equilibrium that evolve through non-adiabatic processes. Numerous techniques for modelling these have been designed and are undergoing rapid further development, usually within individual disciplines. A meeting is to be held to survey the spectrum of molecular dynamics based methods in order to highlight their strengths and weaknesses and to establish fundamental connections between them.

Monday-Friday, July 14-25, 2008 African School on Electronic Structure Methods and Applications *

Organization: ICTP
Location: African Institute for Mathematical Sciences, Cape Town, South Africa
Contact: smr1979@ictp.it

Monday-Friday, July 7-11, 2008 15th International Conference on Luminescence and Optical Spectroscopy of Condensed Matter

Organization: University of Lyon
Location: Lyon, France
Description: The scope of the conference covers theoretical and experimental aspects of luminescence phenomena in both bulky and nano-crystals of organic and inorganic materials. Insulators, semiconductors, disordered and amorphous materials, clusters and nano-clusters are included. The meeting will include invited lectures, contributed presentations and posters of the following topics: # 1- Nature of luminescence centres, excited-state dynamics, energy transfer, thermo-luminescence, # 2- Excitons, polaritons and collective phenomena, # 3- Optical spectroscopy in molecular and biological systems, # 4- Disordered and amorphous materials,#5- Nanocrystals, quantum-structured materials and micro-cavities, # 6- Single molecule, single-particle and quantum-dot spectroscopy, # 7- Near-field microscopy and spectroscopy, # 8- Transient phenomena and coherent processes; picosecond and femtosecond spectroscopy, # 9- High-density excitation and nonlinear effects in optical processes, # 10- Non-radiative processes and non-equilibrium phonon effects; hot luminescence, # 11- Electric field induced, organic and inorganic electroluminescence, OLED and FED, # 12- New luminescent materials, new synthesis, new methods, new phenomena, and # 13- Applications in technology and related topics. As in the previous ICL Conferences, all accepted manuscripts will be published in a special issue of Journal of Luminescence.

Wednesday-Friday, July 2 - August 1, 2008 Summer School on Multiferroic Materials and Beyond

Organization: International Center for Materials Research at the University of California, Santa Barbara
Location: Santa Barbara, California
Contact: Jennifer Ybarra, ybarra --> icmr.ucsb.edu
Applications due: Tuesday, April 1, 2008
Description: The goal of the school will be to present a comprehensive picture of the state of the art in the field of multiferroic oxides with an emphasis on the theory of the coexistence and mutual interaction of different orders and fundamental aspects of the broken symmetries, the search for new compounds exhibiting magneto-electric coupling and multiferroicity, and the novel physical phenomena that result - for instance, extremely complex magnetic phase diagrams, ferroelectricity induced by magnetic order, the rotation or complete reversal of the ferroelectric polarization in magnetic field, ferromagnetic order induced by electric as well as magnetic fields, and the discovery of new elementary excitations. The summer school is designed to encourage cross-fertilization of ideas among the participants.

Monday-Friday, June 30 - July 18, 2008 2008 Boulder Summer School Strongly Correlated Materials

Location: Boulder, Colorado
Contact: Colin Broholm, Piers Coleman, Allan MacDonald, Ashvin Vishwanath
Description: The 2008 Boulder school presents a leading team of experimental and theoretical condensed matter physicists to lecture on diverse aspects of this burgeoning field of research. The school will focus primarily on pedagogy, seeking to provide students with a firm foundation in the key theoretical and experimental methods, with extensive opportunities for informal and detailed discussion. Topics to be covered include fundamentals of Fermi liquid theory, magnetism and low dimensional materials, organic, oxide and heavy electron materials, diverse methods of spectroscopy and transport measurements and the link with strongly correlated physics of atom traps.

Monday-Friday, June 30 - July 4, 2008 Low-Energy Electrodynamics in Solids 2008

Organization: The University of British Columbia and Simon Fraser University
Location: Four Seasons Resort, Vancouver-Whistler, British Columbia
Applications due: Saturday, March 1, 2008
Description: The University of British Columbia and Simon Fraser University are pleased to host the International Conference on Low-Energy Electrodynamics in Solids 2008 (LEES 08), Vancouver-Whistler, British Columbia, June 30 - July 4, 2008. LEES 08 will be a forum for the interdisciplinary discussion of the low-energy electrodynamics of solids, at both the theoretical and experimental level, with specific emphasis on the electronic and magnetic properties of quantum materials. The conference will be held at the Four Seasons Resort in Whistler village, located 130 km from the city of Vancouver. Whistler will host the 2010 Olympic Winter Games and is a spectacular mountain resort in the summer. Early registration is advised, as participation is limited to about 80 attendees. The registration deadline is March 1, 2008. Please visit the conference website for on-line registration and additional information concerning program and accommodation: www.ampel.ubc.ca/lees08

Friday-Tuesday, June 27 - July 1, 2008 8th Liquid Matter Conference

Location: Lund, Sweden
Applications due: Friday, February 15, 2008
Description: The meeting consists of a series of invited lectures together with contributed oral and poster presentations.

Tuesday-Friday, June 24-27, 2008 12th European Conference on Physics of Magnetism

Location: Poznan, Poland
Abstracts due: Saturday, March 1, 2008
Description: The Conference is meant as an international forum for the presentation and discussion of novel scientific ideas, in a field of broadly understood magnetic phenomena, experimental results and new magnetic materials. A special emphasis will be focused on: 1. Strongly Correlated Electrons and High Temperature Superconductivity 2. Quantum and Classical Spin Systems 3. Magnetic Structure and Dynamics 4. Spin Electronics and Magneto-Transport 5. Nano-structure, Surfaces, and Interfaces 6. Soft and Hard Magnetic Materials 7. Applications

Wednesday-Friday, June 18-20, 2008 Recent Developments in Electronic Structure*

Organization: University of Illinois
Location: Materials Research Laboratory, Urbana, Illinois
Contact: David Ceperley, Local Chair, workshops@mcc.uiuc.edu
Description: The program will consist of invited oral presentations and contributed posters describing new methods for computing previously inaccessible properties, breakthroughs in computational efficiency and accuracy, and novel applications of these approaches to the study of molecules, liquids, and solids.
Notes: This year marks the 20th anniversary of this workshop series.

Monday-Friday, June 16-20, 2008 Theoretical and Computational Chemistry Summer School

Organization: Theoretical and Computational Chemistry Reference Network)
Location: Universitat de Barcelona, Barcelona, Spain
Contact: szafra-->fbg.ub.es
Applications due: Friday, May 30, 2008
Registration cost: 150.00 Euro
Description: The Theoretical and Computational Chemistry Summer School is an initiative of the Catalan Theoretical and Computational Chemistry Reference Network with the intention of creating a tool for the diffusion of the latest developments in the field of chemistry today, with special emphasis on the role played by the different branches of theoretical chemistry in the comprehension and modelling of the phenomena involved. We also believe that it is important to provide a forum for learning about the work being carried out by the different research groups that make up the network. Our purpose is therefore to maintain ―within the specific possibilities of each research subject― an equilibrium between the Network members and external scientists in the teaching team. The international scope of the school, which will be conducted in English, will be further enhanced by the participation of foreign professors.
Notes: MCC is offering travel support for this event.

Sunday-Friday, June 8-13, 2008 2008 Gordon Conference on Physics Research and Education

Organization: Bryant University
Location: Smithfield, Rhode Island, USA
Description: The 2008 Gordon Research Conference on Physics Research and Education, the fifth in this series of conferences, will focus on the expanding and deepening role of computers in physics research and instruction, with particular emphasis on undergraduate education. The purpose of this conference is to survey how computational physics is currently being used, to identify problems where computation helps students understand key physics concepts, and to assess the effectiveness of computational-physics instruction. The conference will highlight current efforts to incorporate computational physics and other computer-based methods (such as simulations and visualizations) into the physics classroom. The format of the conference - which will include invited plenary sessions, contributed poster presentations, and generous amounts of unscheduled time for informal discussions - is specially designed to promote dialogue and cross-fertilization of ideas between educators and researchers at the forefront of their fields, including researchers in physics education. College and university faculty, research associates (postdocs), computational-physics textbook authors, curriculum and educational software developers, and graduate and undergraduate students are invited to participate.

Saturday-Sunday, June 7-1, 2008 XXXVII International School on the Physics of Semiconducting Compounds Jaszowiec 2008

Location: Ustron-Jaszowiec, Poland
Applications due: Friday, March 14, 2008
Registration cost: 480.00 USD
Notes: MCC is offering travel support for this event.

Tuesday-Friday, June 3-6, 2008 Chaotic Modeling and Simulation International Conference (CHAOS2008)

Location: Chania, Crete, Greece
Description: The general topics and the special sessions proposed for the Conference (Chaos2008) include but are not limited to: Chaos and Nonlinear Dynamics, Stochastic Chaos, Chemical Chaos, Data Analysis and Chaos, Hydrodynamics, Turbulence and Plasmas, Optics and Chaos, Chaotic Oscillations and Circuits, Chaos in Climate Dynamics, Geophysical Flows, Biology and Chaos, Neurophysiology and Chaos, Hamiltonian systems, Chaos in Astronomy and Astrophysics, Chaos and Solitons, Micro- and Nano- Electro-Mechanical Systems, Neural Networks and Chaos, Ecology and Economy.

Monday-Friday, May 26 - June 6, 2008 SUSSP 2008 on High Pressure Physics

Organization: University of Edinburgh
Location: Sabhal Mòr Ostaig Gaelic College, Isle of Skye, Island of Skye, Scotland
Contact: Malcolm McMahon
Applications due: Saturday, March 1, 2008
Registration cost: 750.00 BPS
Notes: MCC is offering travel support for this event.

Friday-Wednesday, May 23-28, 2008 Topological & Geometric Graph Theory

Location: Paris, France
Contact: Patrice Ossona de Mendez, pom@ehess.fr

Monday-Friday, May 12-16, 2008 Modern Concepts for Creating and Analyzing Surfaces and Nanoscale Materials

Location: Hotel Eden Roc, Costa Brava, Girona, Spain
Contact: Kristen Fichthorn, Matthias Scheffler, fichthorn -- > psu.edu; scheffler --> fhi-berlin.mpg.de
Applications due: Friday, February 29, 2008
Registration cost: 620.00 euro
Notes: MCC is offering travel support for this event.

Monday-Friday, May 12-16, 2008 Workshop on Modern Concepts for Creating and Analyzing Surface and Nanoscale Materials

Location: Hotel Eden Roc, Girona, Spain
Contact: Kristen Fichthorn, fichthorn-->psu.edu
Registration cost: 620.00 euro
Description: This is a Marie Curie Training Workshop. It is ideally suited for young researchers (graduate students, postdocs, junior faculty) from physics, chemistry, and materials scie

News & Events

Jobs

Past Events

Lectures and Talks

Wednesday, February 6, 2008 Quantum coherence and energy transfer: Quantum dot arrays and photosynthetic complexes*

Thursday, October 18, 2007 Nanoscience and Computer Science in Costa Rica: the National Initiative, Projects and Possible Collaborations*

Thursday, September 27, 2007 Atomistic theory of the electronic and optical properties of self-assembled quantum dots*

Thursday, January 25, 2007 Google’s PageRank and Beyond: The Science of Search Engine Rankings*

Thursday, January 25, 2007 Algorithms behind search engines*

Friday, December 8, 2006 Multiscale modeling of Defect Mechanisms in Materials for Nuclear Energy Applications*

Friday, November 3, 2006 High Pressure Physics of Correlated Materials: Experiment and Theory at LLNL and UCD on Gd and MnO*

Wednesday, November 1, 2006 Treating Manybody Polarization and Manybody Dispersion in Complex Systems: The Quantum Drude Oscillator Formalism*

Friday, September 15, 2006 Simulation of unconventional electronic phases by Quantum Monte Carlo*

Wednesday, September 6, 2006 Determination of intrinsicswitching field distributions inperpendicular recording media*

Thursday, March 9, 2006 The role of first principles calculations in multiscale simulations of iron under irradiation*

Thursday, December 15, 2005 Statistical Physics of Fracture*

Monday, December 12, 2005 Kinetics and thermodynamics of hydrides for reversible hydrogen storage*

Wednesday, November 9, 2005 Numerical methods (and some analysis) for material science applications*

Monday, October 24, 2005 Excited states in semiconductors and insulators: ab inito quasiparticle bandstructures of II-VI compounds, group-III-nitrides and high-k dielectrics*

Tuesday, August 30, 2005 Current technical issues for vertical quantum dot devices

Thursday, April 21, 2005 Modeling in the Middle: Design of Competent and Efficient EvolutionaryAlgorithm

Monday, April 4, 2005 Towards materials specific simulations of high temperature superconductors*

Monday-Friday, February 14-25, 2005 36th Spring School 2005: Magnetism goes Nano (Electron Correlation, Spin Transport, Molecular Magnetism)

Monday, December 6, 2004 Dielectric Properties of Semiconductors by TDDFT*

Thursday, December 2, 2004 Finite-Element Method for Large-Scale Ab Initio Electronic-Structure Calculations -- Informal Discussion*

Wednesday, December 1, 2004 Finite-Element Method for Large-Scale Ab Initio Electronic-Structure Calculations*

Wednesday, September 15, 2004 Formulation of the Anisotropic Coarsening Theory (ACT) and applications to the liquid phase sintering of silicon nitride*

Thursday, August 19, 2004 Coupled Electron-Ion Monte Carlo Method and Application to Metallic Hydrogen*

Thursday, August 12, 2004 Electronic structure by Slater determinant random walks*

Monday, April 12, 2004 Critical dynamics in a funnel-shaped landscape: a Landau-type theory of the glass transition*

Thursday, February 12, 2004 Fast Eigenvalue/Eigenvector Computation for Dense Symmetric Matrices

Tuesday, February 10, 2004 Modeling Elastic and Plastic Deformations in Materials Physics

Monday, February 9, 2004 Control of Exchange Interaction in a Double Dot System*

Friday, January 16, 2004 An informal discussion: What is nano?*

Monday, December 8, 2003 Structural Topology Optimization and Applications*

Monday, November 10, 2003 Critical thickness for ferroelectricity in barium titanate ultrathin films*

Friday, November 7, 2003 Computational challenges and solution algorithms in electronic structure calculations*

Friday, November 7, 2003 Atoms on the Move: Simulating the Properties of Semiconductor Liquids*

Wednesday, October 29, 2003 Electronic transport in Nanostructures from first principles: a simulation tool*

Friday, October 24, 2003 Deriving Plasticity: Attempts at a Theory for Dislocation Patterning and Work Hardening*

Friday, September 12, 2003 Full Multiple Spawning with QM/MM Methods for Excited States: Direct Photodynamics for Large Chromophores in Proteins and Condensed Phases*

Friday, August 29, 2003 Simulating the phase behaviour of polydisperse fluids*

Wednesday, July 2, 2003 New small silicon interstitial clusters*

Wednesday, June 18, 2003 Theory of the tunneling spectroscopy in buried metallic nanoparticles*

Wednesday, May 1, 2002 Fracture patterns and kinetics in deposition of solids*

Monday, March 25, 2002 Tight-Binding for Real Materials*

Wednesday, February 27, 2002 Thermal Activation of Dislocation Motion*

Tuesday, February 26, 2002 Electronic Structure Codes and Methods Development at NERSC*

Friday, October 12, 2001 Real-space multiscale methods in DFT*

Monday, November 6, 2000 Cluster growth from a reversible model of diffusion*

Tuesday, September 5, 2000 Van der Waals interacton between atomic cluster of simple metal and metal surface*

Wednesday, August 16, 2000 Universality in two-dimensional quantum magnets*

Tuesday, August 15, 2000 Generic parallel algorithms for lattice models*

Monday, June 26, 2000 Time Dependant Density-Functional Theory and Si clusters.*

Wednesday, June 21, 2000 Time Dependent Density-Functional Theory and Si clusters.*

Tuesday, May 30, 2000 Stability of Si-interstitial complexes: from point to extended defects*

Monday, March 13, 2000 Parallel supercomputing in science and engineering*

Wednesday, February 23, 2000 Theory of composite-band Wannier states and order-N electronic-structure calculations

Wednesday, February 23, 2000 Molecule-surface Interactions by Design

MCC Visitors

Tuesday-Thursday, February 5-7, 2008 Alan Aspuru-Guzik, Harvard University*

Monday-Friday, September 24-28, 2007 Weidong Sheng, National Research Council, Ottawa, Canada*

Wednesday-Saturday, August 15 - December 15, 2007 Sashi Satpathy, University of Missouri*

Wednesday-Saturday, January 24-27, 2007 Prof. Amy Langville, College of Charleston, South Carolina, Department of Mathematics*

Wednesday-Friday, November 1-3, 2006 Dr. Nicola Spaldin, University of California, Santa Barbara, Materials Department *

Wednesday-Friday, November 1-3, 2006 Dr. Warren Pickett, University of California Davis, Department of Physics *

Tuesday-Saturday, October 31 - November 4, 2006 Dr. Glenn Martyna, IBM TJ Watson Laboratory, Yorktown Heights, New York *

Sunday-Tuesday, September 17-19, 2006 Andreas Berge, Hitachi Global Storage Technologies, San Jose, CA*

Monday-Friday, September 11-15, 2006 Sandro Sorella, SISSA/ISAS, Trieste Italy*

Saturday, August 5, 2006 Haydar Arlsan, Zonguldak Karaelmas Unviersity, Turkey*

Saturday, August 5, 2006 Bothina Hamad, University of Jordan *

Thursday, August 3, 2006 Huajun Fan, Prarie View A&M University*

Friday-Wednesday, June 2-7, 2006 Ivo Souza, UC Berkeley*

Thursday-Saturday, April 6-8, 2006 Shiwei Zhang, Department of Physics College of William and Mary*

Wednesday-Saturday, March 29 - April 8, 2006 Carlo Pierleoni, Physics Dept., University of L’Aquila, Italy*

Thursday, March 9, 2006 Francois Willaime, Service de Recherches de Metallurgie Physique. CEA/Saclay*

Monday, December 12, 2005 Roland Stumpf, Materials Physics, Sandia National Labs, Livermore, CA*

Sunday-Tuesday, October 23-25, 2005 Dr. Patrick Rinke, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany*

Monday-Tuesday, August 29-30, 2005 D.G. Austing, NRC, Ottawa, Canada *

Monday-Thursday, April 18-28, 2005 Carlo Pierleoni, Physics Dept., University of L’Aquila, Italy*

Friday, January 16, 2004 An informal discussion: *What is nano?**