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[paul fons <paul-fons@aist.go.jp>]

I would also second this request.  The documentation for atompaw has not kept pace with it development.  While some parameters are obvious (loggrid, scalarrelativistic), others are not.  In particular guidelines/advice on how to pick projector energies is lacking.  There is also a dichotomy in the examples on the example potentials on Nancy Holzwarth's periodic table (http://www.wfu.edu/%7Enatalie/papers/pwpaw/periodictable/periodictable.html).  Here you can see example input files for atompaw as well as equation of state data for calculations in which the PAW potentials have been used.  The table has two classes of entries the older (labled unmodified in the table) entries all use the Vanderbilt scheme but do not enter any additional projectors/energies while the (newer, recent) entries labled modified entries do introduce such levels.   How to decide on these levels?  It would be great to have a tutorial on this subject (it would answer a lot of people's question).  As of the moment it is a hard resource to use and it shouldn't be as it looks to be very useful.  In my limited tests, it seems to work fairly well, but I feel like I am working a little in the dark.  For example, in the examples folder for the latest version of atompaw there is a Cd example, however the core radius for this PS is set for 2.0 Angstroms.  Why such a small cutoff?  What was the logic behind it?  The answers to how to choose energy levels (I know it is a try and error process) as well as some educated comments about appropriate core radii would go a long way toward the generation and verification of PAW PS.  

Another idea would be to try and generate more elements of the period table as a group and then verifying them by calculating known materials EOS.  Doing this process as a group might lead to a useful table of elements that all can use.

Just my thoughts,

Paul Fons

Paul Fons

Team Leader

Nano-Optics Research Team

paul-fons@aist.go.jp

Center for Applied Near-Field Optics

National Institute of Advanced Industrial Technology

Tsukuba Central 4, Higashi 1-1-1

Tsukuba, Ibaraki Japan 305-8562

tel. +81-298-61-5635

fax. +81-298-61-2939

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On Apr 13, 2007, at 7:53 AM, snow9@llnl.gov wrote:

Guillaume, and others:

I am interested in developing a Ga PAW set with atompaw, but have only just begun using atompaw.  Would you mind sharing what you have for Ga, that I can use as a guideline for my set?  Thanks a million.

-- Ryan

Quoting Guillaume Dumont <dumont.guillaume@gmail.com>:

Dear Paul,

We actually had some trouble generating PAW datasets for Ga with the USPP

package. As you suggest we figured out that the partial core corrections had

a great impact on the physical properties one obtains with datasets

generated with this package. On the other hand, AtomPAW has improved a lot

since the first time I tried it. Personnaly, I find it easier to use than

USPP. There is also a great manual written by M. Torrent that should be

available on the web (is it?).

At the last developper workshop, everyone agreed that a complete table of

PAW should be generated by some of the developpers. So the fact that the

list of elements is more complete with USPP should not be a problem anymore

in the near future.

Guillaume

On 4/10/07, Paul Fons <paul-fons@aist.go.jp> wrote:

 I have tried both methods of generating ultrasoft pseudopotentials and

was under the impression that Nancy Holzwarth's system generated more

reasonable pseudopotentials, but perhaps it was the non-linear core

corrections that were the problem.  Has anyone systematically compared the

two methods?   The USPP pseudopotentials have the advantage that there are a

lot of different input files for the elements already available I have

noted.  On the other hand Nancy Holzwarth's pages have a periodic table

linked with several tens of elements included as well.  On thing that has

bothered me about this table is that none of the input files create new

generalized basis functions (whereas the input file on the abinit PAW page

for O does).    I have generated a PAW potential for Sb and it seemed to

give reasonable results, but I am curious about others experiences.

Dr. Paul Fons

Nano-Optics Reseach Team

Team Leader

National Institute for Advanced Industrial Science & Technology

METI

Center for Applied Near-Field Optics Research (CANFOR)

AIST Central 4, Higashi 1-1-1

Tsukuba, Ibaraki JAPAN 305-8568

tel. +81-298-61-5636

fax. +81-298-61-2939

email: *paul-fons@aist.go.jp*

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-- 

Guillaume Dumont

=========================

guillaume.dumont.1@umontreal.ca

dumont.guillaume@gmail.com

(514) 341 5298

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