[Pw_forum] Four Electron Pseudopotnetial for tin: US vs NC-PP

Giovani Faccin faccin.giovani at gmail.com
Tue May 8 19:45:38 CEST 2012


Dear Sven,

I've built a few pseudopotentials in the past to study hybrid clusters. On
those calculations I found that the TM pseudization succeeds at generating
pseudopotentials much more often than the rrkj pseudization. Perhaps you
could try it, and if it works, then use the cutoff parameters data that
worked out with TM as a guide to try to generate a pseudo using rrkj,
should you really have to stick to it.

That said, a few ideas that might help:

1 - On the 6D line, why a negative number of electrons? Sorry if I'm
mistaken, but shouldn't that number be positive?

2 - On this same line, why not use the reference energy (0.00), since it's
a bound state, as done in 5S and 5P?

3 - If everything else is ok, the cutoff parameters (the 2.50 and 2.70 guys
in the 6th and 7th columns) are usually to blame when generation fails.
You'll have to explore those parameters in order to find a good
combination. To aid in that, plot the all electron wavefunctions generated
and look at them. That will give you an idea of reasonable values to use
for the cutoff.

Best,

Giovani M. Faccin
UFMS/Brazil


2012/5/8 Sven Heiles <Heiles at cluster.pc.chemie.tu-darmstadt.de>

> Dear Quantum Espresso users.
>
> Our group is dealing with the global optimizations of clusters using
> Quantum Espresso. In the moment we investigate
> the Mn-Sn system for which it is known that a considerable charge
> transfer between Mn(positive) and Sn(negative) occurs. In order to model
> the clusters in a finite time it would be useful only to use a PP for
> the four valence electrons of tin while for Mn it is no problem
> to use 15 electrons (only one or two Mn are used). The Mn-PP is
> generated using the rrkjus fitting routine but the Sn-PP generation
> always fails if only four electrons
> are used for the ultra-soft PP. We tested to generate the 14 electron
> US-PP for tin in analogy to the Pb-US-PP found in the QE PP library and
> were able to generate a PP.
> Unfortunately, that many electrons are not of much use in our global
> optimization calculations.
> On the other hand the generation of a NC-PP with four electrons for tin
> is able to reproduce bulk and
> dimer properties but a similar procedure for Mn is not of much use. Does
> someone has an idea what the problem for the 4 electron
> US-PP for tin could be? Please find the generation parameters below.
>
> All the best
>
> Sven
>
> &input
>     title='Sn',
>     zed=50.0,
>     rel=1,
>     iswitch=3,
>     config='[Kr] 4d10.0 5s2.0 5p2.0 6d-2.0',
>     dft='LDA',
>  /
>  &inputp
>     lloc=2,
>     pseudotype=3,
>     file_pseudopw='Sn.pz-rrkjus.UPF',
>     author='',
>  /
> 5
> 5S  1  0  2.00  0.00  2.50  2.50
> 5S  1  0  0.00  0.05  2.50  2.50
> 5P  2  1  2.00  0.00  2.70  2.90
> 5P  2  1  0.00  0.05  2.70  2.90
> 6D  3  2 -2.00  0.15  2.70  2.70
>
>
> --
> Dipl. Ing. Sven Heiles
> Technische Universität Darmstadt
> AK Schäfer
> Eduard-Zintl-Institut
> Petersenstraße 20
> D-64287 Darmstadt – Germany
>
> Phone: ++49-(0)6151-164397
> Fax: ++49-(0)6151-166024
> Web:http://www.tu-darmstadt.de/fb/ch/cluster/schaefer.tud
>
> _______________________________________________
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> Pw_forum at pwscf.org
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>
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