[Pw_forum] optimization and pseudo potentials

[James Mao]

Hi Giuseppe,

The PPs part in my input is:

ATOMIC_SPECIES
 Al 26.98 Al.pbe-tm-gipaw-dc.UPF
 O  16.00  O.pbe-tm-new-gipaw-dc.UPF
 P  30.97  P.pbe-tm-new-gipaw-dc.UPF

I got these PP files from here:

https://sites.google.com/site/dceresoli/pseudopotentials

I always use them for GIPAW calculations and they works fine. Never realized they might not 
be suitable for other types of calculations like optimization. So I think this is a good chance 
for me to get educated. lol

Thanks again! 

Best,
James


-----Original Message-----
From: pw_forum-bounces at pwscf.org [mailto:pw_forum-bounces at pwscf.org] On Behalf Of Giuseppe Mattioli
Sent: Tuesday, January 28, 2014 2:15 PM
To: pw_forum at pwscf.org
Subject: Re: [Pw_forum] optimization and pseudo potentials


Dear James
Hard to help you without seeing the PP files or their generation input files.
Where did you find the PPs? I do not spot them in the online library...
Yours
Giuseppe

Giuseppe Mattioli
ISM-CNR
Italy

Quoting James Mao <xjamesmao at gmail.com>:

> Dear users,
>
>
>
> I am trying to calculate NMR chemical shifts by GIPAW for a crystal 
> (with atoms Al, P, O). The pps I used
>
> with GIPAW are "pbe-tm-gipaw-dc" sets. I did get reasonable results.
>
>
>
> For a second step I tried to optimize the structure. I noticed if I 
> still used the gipaw pps, the optimization
>
> process is completely wrong. In vc-relax calculations the cell volume 
> keeps shrinking to 67% of original
>
> volume (which is from experimental structure). While I changed the pps 
> to "pbe-n-kjpaw" set, vc-relax
>
> gave reasonable results.
>
>
>
> I would be very thankful if someone can explain a little bit for me 
> what kind of pps are not suitable for
>
> optimization so in future I can avoid similar mistake? Any helps will 
> be greatly appreciated.
>
>
>
> Best regards,
>
> James Mao
>
>
>
> Postdoc associate
>
> Department of Chemistry,
>
> University of Pittsburgh


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    CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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