How to build PAW atomic data for Abinit using USPP generator

Current version of USpp2Abinit :v2.4.0

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 as follows:
- We patch D. Vanderbilt's USPP package in order to make it generate PAW atomic data in Abinit's format (in addition to ultrasoft pseudopotentials).
- "Patched" USPP is directly useable to produce PAW atomic data from normal USPP input files.

Many thanks to D. Vanderbilt for having given us the opportunity to use USPP package.

1. What you need:

USPP ultrasoft pseudopotentials generator (version 7.3.6 or higher)
This code is written in Fortran 77
USpp2Abinit add-on tu USPP
This code is written in Fortran 90
A Linux/Unix workstation with (at least) following tools:
Fortran 90 compiler with F77 libraries, sed stream editor, make utility.

We suppose for the following that the reader is familiar with the use of USPP package.
If not, first take at look at the complete user's guide written for it.

2. Preliminary steps: patching USPP

Download USPP package. You can find it here. Be sure to download version 7.3.6 or higher (including some modif. for Abinit).
Extract USPP (in some /uspp-xyzdirectory)

Download USpp2Abinit 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 USpp2Abinit with versions 4.6.x-6.0.x of ABINIT.
Here USpp2Abinit for Abinit v4.3.x-v.4.5.x (buggy !, only for tests).

Extract Uspp2Abinit into USPP directory (in /uspp-xyz/USpp2Abinit.vx.y.z directory).
Note that you also get a new /uspp-xyz/utils-uspp directory

Go into /uspp-xyz/Uspp2Abinit.vx.y.z directory and edit Makefile file; modify it according to your machine specifications.
Into /uspp-xyz/Uspp2Abinit.vx.y.z directory,

Type: make
It compiles a patched version of USPP (with Abinit PAW add-ons) and creates runatom.x in /uspp-xyz/USpp2Abinit.vx.y.zdirectory
Type : make install
It installs "patched" runatom.x into /uspp-xyz/Bin directory

Optional:Type : make clean it cleans up /uspp-xyz/Uspp2Abinit.vx.y.z directory
or : make clean_all it cleans up /uspp-xyz/Uspp2Abinit.vx.y.z and /uspp-xyz/Source directories

At this stage you get a patched version of USPP package; you can use it like original USPP.

3. Generating a PAW "pseudopotential file" for Abinit:

Simply use USPP as if you wanted to generate an ultrasoft pseudopotential !

Go into /uspp-xyz/Work directory; browse down sub-directories, selecting chemical specie and density functional (LDA, GGA).
Type make clean; make
If you encounter some error during execution, look for an error message in the ??_ae.out or ??_ps.out file; if the error message is not explicit enough, look at Doc/TUTORIAL (most of the problems are referenced inside).

And you get a X.abinit.paw file (X=generic name) directly useable by Abinit !
Additional options:

A file named uspp2abinit.dat can be added in the working directory to pass arguments to the USpp2Abinit converter.
Here, an example of this file, with details on the different keywords.

Note: if you want to use Abinit prior version 5.2 (especially v4.6.x), you HAVE TO use the COMPAT46 keyword in uspp2abinit.dat file.

Note for experienced users:
If you want to use "Real Space Optimisation" to improve the behaviour of non-local projectors, you have to use specific keywords in uspp2abinit.dat file.

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 in uspp2abinit.dat file.
The efficiency of Real Space Optimization strongly depends on the non-local projectors produced by USPP (it can be sometimes unuseful); only experienced users should use it...

4. Additional remarks:

You can as a first step use input files (*.adat files) distributed by D. Vanderbilt on his web site.
But we recommend to make additional tests before using those input files. PAW formalism is a bit different from US pseudopotentials one and can induce a different behaviour of atomic data.
The choice of a density functionalis limited by functionals included in USPP package and in Abinit.
To be used a density functional model must be incorporated into both packages.
Only four functionals are programmed in USPP and Abinit together: Ceperley-Adler (LDA), Wigner (LDA), Hedin-Lundqvist (LDA), Perdew-Burke-Ernzerhof 96 (GGA)
In order to check the validity of atomic data produced by USPP, a simple test is the comparison of the logarithmic derivatives of wave functions (exact ones compared to pseudo ones).
A simple PYTHON script pltlogd is provided within USpp2Abinit package in /uspp-xyz/utils-uspp directory to plot these derivatives. It uses the ??.logd file produced by USPP.
Just type: pltlogd file.logd l, where l is an angular momentum (0, 1, 2, or 3).

5. References:

[1] Soft Self-Consistent Pseudopotentials in a Generalized Eigenvalue Formalism,
D. Vanderbilt, Phys. Rev. B 41 (Rapid Communications), 7892 (1990)

[2] Implementation of Ultra-Soft Pseudopotentials in Ab-initio Molecular Dynamics,
K. Laasonen, R. Car, C. Lee, D. Vasnderbilt, Phys. Rev. B 43 (Rapid Communications), 6796 (1991)

[3] From ultrasoft pseudopotentials to the projector augmented-wave method,
G. Kresse, D. Joubert, Phys. Rev. B 59, 1758 (1999)

[4] Real-space implementation of nonlocal pseudopotentials for 1st-principle total-energy calculations,
R.D. King-Smith, M.C. Payne, 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. Contacts:

In case of problem or questions contact the authors. Marc Torrent FranÃ§ois Jollet DÃ©partement de Physique ThÃ©orique et AppliquÃ©e CEA, DAM, DIF F-91127 Arpajon France

Last modification : may 11th 2010