[Pw_forum] optimization and pseudo potentials

[Giuseppe Mattioli]

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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    Giuseppe Mattioli
    CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
    v. Salaria Km 29,300 - C.P. 10
    I 00015 - Monterotondo Stazione (RM)
    Tel + 39 06 90672836 - Fax +39 06 90672316
    E-mail: <giuseppe.mattioli at ism.cnr.it>