ABINIT, PAW input variables:

List and description.

This document lists and provides the description of the name (keywords) of the input variables for runs based on the Projector Augmented Waves methodology, to be used in the main input file of the abinis code.

The new user is advised to read first the new user's guide, before reading the present file. It will be easier to discover the present file with the help of the tutorial.

When the user is sufficiently familiarized with ABINIT, the reading of the ~ABINIT/Infos/tuning file might be useful. For response-function calculations using abinis, the complementary file ~ABINIT/Infos/respfn_help is needed.

Copyright (C) 1998-2004 ABINIT group (DCA, XG, RC)
This file is distributed under the terms of the GNU General Public License, see ~ABINIT/Infos/copyright or http://www.gnu.org/copyleft/gpl.txt .
For the initials of contributors, see ~ABINIT/Infos/contributors .
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Files that describe other input variables:

Content of the file : alphabetical list of PAW input variables.


A.
B. bxctmindg  
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
M.
N. ngfftdg  
O.
P. pawecutdg   pawlcutd   pawmixtyp   pawnphi   pawntheta   pawnzlm   pawsphmix   pawvlbox   pawxcdev  
Q.
R.
S.
T.
U.
V.
W.
X.
Y.
Z.



bxctmndg
Mnemonics: BoX CuT-off MINimum for the Double Grid (PAW)
Characteristic:
Variable type: real parameter
Default value: 2.0

Needed only when usepaw=1.
The box cut-off ratio is the ratio between the wavefunction plane wave sphere radius, and the radius of the sphere that can be inserted in the FFT box, in reciprocal space.
In order for the density to be exact, this ratio should be near two. If one uses a smaller ratio, one will gain speed, at the expense of accuracy. In case of pure ground state calculation (e.g. for the determination of geometries), this is sensible. However, the wavefunctions that are obtained CANNOT be used for starting response function calculation.



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ngfftdg
Mnemonics: Number of Grid points for Fast Fourier Transform : Double Grid
Characteristic:
Variable type: integer array ngfftdg(3)
Default : 0 0 0 (so, automatic selection of optimal values)

Needed only when usepaw=1.
This variable as the same meaning as ngfft (gives the size of fast fourier transform (fft) grid in three dimensions) but concerns the "double grid" only used for PAW calculations.



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pawecutdg
Mnemonics: PAW - Energy CUToff for the Double Grid
Characteristic: ENERGY
Variable type: real parameter
Default : 1.25 times ecut

Needed only when usepaw=1.
Define the energy cut-off for the fine FFT grid (that allow to transfer data from the normal, coarse, FFT grid to the spherical grid around each atom).
pawecutdg must be larger or equal to ecut. If equal to it, then no fine grid is used. The results are not very accurate, but the computations proceed quite fast.
The default value is sometimes a bit too low, but does not slow down the computation. The choice made for this variable DOES have a bearing on the numerical accuracy of the results, and, as such, should be the object of a convergence study. The convergence test might be made on the total energy or derived quantities, like forces, but also on the two values of the "Compensation charge inside spheres", a quantity written in the log file.



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pawlcutd
Mnemonics: PAW - 1+L angular momentum used to CUT the development in moments of the Densitites
Characteristic:
Variable type: integer parameter
The default is 10

Needed only when usepaw=1.
The expansion of the densities in angular momenta is performed up to l=pawlcutd-1.
The choice made for this variable DOES have a bearing on the numerical accuracy of the results, and, as such, should be the object of a convergence study. The convergence test might be made on the total energy or derived quantities, like forces, but also on the two values of the "Compensation charge inside spheres", a quantity written in the log file.



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pawmixtyp
Mnemonics: PAW - MIXing TYPe during electronic iterations
Characteristic:
Variable type: integer parameter
The default value is 1

Needed only when usepaw=1.
The choice made for this variable determine how the spherical part of the density is mixed during electronic iterations.




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pawnphi
Mnemonics: PAW - Number of PHI angles used to discretize the sphere around each atom.
Characteristic:
Variable type: integer parameter
The default is 13

Needed only when usepaw=1.
Number of phi angles (longitude) used to discretize the data on the atomic spheres. This discretization is completely defined by pawnphi and pawntheta.



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pawntheta
Mnemonics: PAW - Number of THETA angles used to discretize the sphere around each atom.
Characteristic:
Variable type: integer parameter
The default is 12

Needed only when usepaw=1.
Number of theta angles (latitude) used to discretize the data on the atomic spheres. This discretization is completely defined by pawntheta and pawnphi.



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pawnzlm
Mnemonics: PAW - only compute Non-Zero LM-moments of spherical density
Characteristic:
Variable type: integer parameter
Default value: 1

Needed only when usepaw=1.
Concerns the computation of the spherical density (named rho_1 - rho_tild_1).
If set to 0, all lm-moments of the spherical density are computed at each electronic iteration br> If set to 1, only non-zero lm-moments of the spherical density are computed at each electronic iteration (they are all computed at first iteration then only the non-zero ; thus the first iteration is more cpu expensive)



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pawsphmix
Mnemonics: PAW - SPHerical part MIXing factor
Characteristic:
Variable type: real parameter
Default value: 0.6

Needed only when usepaw=1, and pawmixtyp > 0.
Mixing factor for the spherical part of total PAW energy. Quantities are mixed according to the following simple mixing: Xnew = (1-pawsphmix * Xold) + Xpredicted .



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pawvlbox
Mnemonics: PAW - compute VLoc potential in the whole fft BOX
Characteristic:
Variable type: integer parameter
Default value: 0

Needed only when usepaw=1.
If set to 0, the local potential is computed only in a sphere contained in the FFT box (and set to zero outaide this sphere)
If set to 1, the local potential is computed in the whole FFT box - usefull for testing purpose only
Choice 0 is sufficient in most cases



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pawxcdev
Mnemonics: PAW - choice for eXchange-Correlation DEVeloppment (spherical part)
Characteristic:
Variable type: integer parameter
Default value: 1

Needed only when usepaw=1.

Be careful: GGA requires pawxcdev > 0



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Goto : ABINIT home Page | Welcome | Suggested acknowledgments | List of input variables | Tutorial home page | Bibliography
Help files : New user's guide | Abinis (main) | Abinis (respfn) | Mrgddb | Anaddb | AIM (Bader) | Cut3D