How to build PAW atomic data for ABINIT
using AtomPAW generator
Current
version of AtomPAW2Abinit :v3.3.0
-
Available for Abinit
v5.4.3+
See this note for use with previous versions of
Abinit
To obtain PAW atomic
data for ABINIT we proceed in two steps:
- We first use the AtomPAW
atomic data generator to obtain a set of projectors and basis functions.
- Then we
transform these data into a "pseudopotential file" for ABINIT.
Many
thanks to N.
Holzwarth for the fruitful collaboration and for having given us
the opportunity to take part in AtomPAW project.
1. What you need:
2. Preliminary steps:
-
- Download the AtomPAW
package (at least version 2.2). You can download the
official version.
See this note for use of AtomPAW with previous
versions of ABINIT.
- Take
a look at the user's guide for AtomPAW.
Get it here.
- Compile AtomPAW
using a Fortran 90 compiler. You can use make.inc
file(s) included in the package.
To compile AtomPAW, just copy make.xxx
to make.inc
and type make atompaw.
You will need to link the Lapack v3
package.
At this stage you have an executable named "atompaw".
- Download AtomPAW2Abinit package. You can find
it here (fully compatible with ABINIT v6.1.0+, partly compatible with ABINIT v5.4.3+).
See this note for use of AtomPAW with
versions 4.6.x-6.0.x of ABINIT.
Here
AtomPAW2Abinit for Abinit v4.3.x-v.4.5.x (buggy! only for tests).
- Compile AtomPAW2Abinit using a Fortran 90
compiler. You have to modify the Makefile
included in the package to match your compiler.
At this stage you have an executable named "atompaw2abinit".
3. Generating a PAW "pseudopotential file" for ABINIT:
- Create
a work directory ; use it for all that follows.
- Edit the input file for AtomPAW. You can find an example here (Oxygen). Input file syntax is explained in
the user's guide.
- In the
following example:
- Chemical species is named X.
Corresponding input file is named X.input.
Short explanation of the content of this input file
- Run
AtomPAW: atompaw < X.input
AtomPAW generates several files; only one is used for Abinit psp
generation; others are useful to check the accuracy and
transferability of the atomic data (see below).
- Run
AtomPAW2Abinit: atompaw2abinit
The
program asks you for two file names:
Atomic data
file: X.atomicdata
(in this example)
Psp file for Abinit: Name of your choice
Then
the program asks for the following input:
- Do you want to include compensation charge density in eXchange-Correlation terms ? (no=recommended for Abinit 6.1.0+)
Before Abinit version 6.1.x, only choice "YES" is usuable... But this choice can produce innacurate PAW datasets under some (rare) circumstances.
Note that this question only appears when AtomPAW v2.3 or higher has been used (otherwise compensation density is automatically included in XC terms).
- Do we use «Real Space Optimisation» to
improve the behaviour of non-local projectors ?
Real Space Optimisation improve
the development of non-local projectors by "smoothing" their
development over large G vectors (introducing a "controlled" error). It
has been proposed by King-Smith and al. (see [4] below).
The
scheme is governed by 3 parameters: Gmax (=2·Ecut**2), Gamma and
Wl ; the user has to give these parameters when AtomPAW2Abinit asks for
them. The efficiency of Real Space Optimization strongly depends on the
non-local projectors produced by AtomPAW (it can sometimes be detrimental); only experienced users should use it.
- Should the
atomic data be transferred to a (reduced) logarithmic grid ? (yes=recommended)
Only
required when AtomPAW atomic data are given on a regular radial grid. In
that case, the regular grid can sometimes be very large which can be
CPU consuming when running ABINIT. Transferring all data into a smaller
logarithmic grid (except non-local projectors for technical reasons)
can avoid this. The logarithmic grid is defined by:
r(i>1)=a.exp[b.(i-2)] and r(1)=0 ; The user has to give the size of
the grid and the «logarithmic step» (b in the above formula).
End: the "pseudopotential file" for ABINIT has been created.
4. How to check the validity of PAW atomic data ?
Iteratively
check the following quantities before accepting a given set of
projectors and basis functions:
1- The PAW logarithmic
derivatives for each atom should agree with the all-electron values
within the energy range of interest. See files logderiv.i
2- The core electron density ncore should be sufficiently small
for r>rc. See file
density
3- The plane-wave cut-offs needed to converge the calculation
(which can be determined with the help of the Fourier-space functions
Fnili(q)), should be consistent with the computer resources available
for the solid state calculations. See files tprod.i
4- For the material of interest, several solid state
calculations should give reasonable results.
-
| We strongly advise users to follow the
guidelines given by the user's guide (see
"Advice for use" chapter); it can be considered as an AtomPAW tutorial |
5. References:
[2]
Complete
projector functions for the projector augmented wave (PAW) method of
electronic structure calculations,
N. A. W. Holzwarth, G. E.
Matthews, A. R. Tackett and R. B. Dunning, Phys. Rev. B 57,
11827-11830 (1998).
[4] Real-space implementation
of nonlocal pseudopotentials for 1st-principle total-energy
calculations,
R.D. King-Smith, M.C. Payne and J.S. Lin, Phys.
Rev. B
44, 13063 (1991)
[5]
Implementation of the projector augmented-wave method in the ABINIT
code: Application to the study of iron under pressure,
M. Torrent,
F. Jollet, F. Bottin, G. Zerah and X. Gonze, Comput. Mater. Sci.
42, 337 (2008)
6. Examples of AtomPAW atomic data for ABINIT:
You
can find a lot of input files on the AtomPAW web site (the periodic table
is here).
-
7. Contacts:
In case of problem or questions
contact the authors.
Marc Torrent
François Jollet
Département de Physique Théorique et Appliquée
CEA, DAM, DIF
F-91127 Arpajon
France
Last modification : may 07th 2010