Dear James I did not know that Davide put his own PP library online... Thanks for sharing! As far as I can see, there seems to be no intrinsic reason because these pseudopotentials should behave so badly in vc-relax (or even relax) calculations. But they are Troullier-Martins norm conserving pseudopotentials (tm-gipaw), and they may be quite harder than PAW pseudopotentials with non-linear core corrections (n-kjpaw). Have you tried to check the convergence for ecutwfc? HTH Giuseppe
Giuseppe Mattioli ISM-CNR Italy Quoting James Mao <xjamesmao at gmail.com>: > 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 > > > -- > ******************************************************** > - Article premier - Les hommes naissent et demeurent libres et ?gaux > en droits. Les distinctions sociales ne peuvent ?tre fond?es que sur > l'utilit? commune > - Article 2 - Le but de toute association politique est la > conservation des droits naturels et imprescriptibles de l'homme. Ces > droits sont la libert?, la propri?t?, la s?ret? et la r?sistance ? > l'oppression. > ******************************************************** > > 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> > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum -- ******************************************************** - Article premier - Les hommes naissent et demeurent libres et ?gaux en droits. Les distinctions sociales ne peuvent ?tre fond?es que sur l'utilit? commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la libert?, la propri?t?, la s?ret? et la r?sistance ? l'oppression. ******************************************************** 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>