[Pw_forum] O.pw91-van_ak.UPF oxygen pseudopotential

[Nicola Marzari]

Dear Bertran,

others more conversant with the UPF format might answer better
(http://www.quantum-espresso.org/wiki/index.php/Unified_pseudopotential_format)
but I suspect that a large Rcut means just that the ultrasoft pseudo was 
not generated
starting from a norm-conserving pseudo, but directly from an 
all-electron calculation,
and the principal quantum number is exactly what it says - i.e. the 
principal quantum
number (of the all electron calculation).

Note that we found some oddities with the oxygen pseudopotential 
generated from
David Vanderbilt's published table - we put a comment in the PBE version 
of it:
http://quantum-espresso.org/pseudo/upfdetails.php?upf=O.pbe-van_bm.UPF

The Bernd Meyer version above seems to have a smaller cutoff radius than the
version converted by Axel (ak); still, I would be extra careful before 
using this, and
consider instead the rrkj PBE pseudo of Andrea Dal Corso.

I'd actually suggest to remove the O.pbe-van_bm.UPF from the pseudo 
table, alhough
not sure what to do on the pw91-van_ak .

   
                nicola


Bertrand SITAMTZE wrote:
> Dear all,
>
>  I wanted to use the pseudopotential "O.pw91-van_ak.UPF" downloaded 
> from the QE espresso web site.. But there is something strange: In the 
> human-readable section
>  of the file, there are two unusual things:
>
> 1) The Rcut is set to 10.0000000. Is it not too high? According to me, 
> this number should be between 0..90 and 1.20
> 2) The pricipal quantum number of the 2S state is set to 2,
>    and I think  it should be 1.
>
> I would like you to shed more light on this issue.
> A comment from somebody who has already use this pseudopotential is 
> welcomed.
>
> Also, I would like you to confirm, as Lorenzo
> wrote some days ago, that a pseudowavefunction with
> opposite sign of that of all electron wavefunction is still
> valid
>
> Thanks for your reaction
>
>
> ********************
> Bertrand SITAMTZE
> PhD Student
> Department of physics
> University of Yaoundé I-Cameroon
> ************************
>
>
> ------------------------------------------------------------------------
>
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Prof Nicola Marzari   Department of Materials Science and Engineering
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