Dear Giuseppe, I tried ecutrho as 8 or 12 times of ecutwfc=30 for ultrasoft PP. Also tried norm conserving PP with ecutwfc=70 and ecutrho=280. The c/a ratio is still far off from the expected 1.4142. Very confused.
Regards, Wei Wei Lai Michigan State University East Lansing, MI 48824 On Wed, Mar 28, 2012 at 10:43 AM, Giuseppe Mattioli < giuseppe.mattioli at ism.cnr.it> wrote: > > Dear Wei > > > > &system > > ibrav= 7, celldm(1) = 5.6298, celldm(3) = 1.4, nat= 2, ntyp= 2, > > ecutwfc =30, input_dft='pw91' > > / > > > ATOMIC_SPECIES > > Mg 24.305 Mg.pw91-np-van.UPF > > O 15.999 O.pw91-van_ak.UPF > > You are using ultrasoft pseudopotentials. You should explicitly assign a > value to the ecutrho > parameter (&system list). The default value is 4*ecutwfc, and it is a good > value for norm conserving > PPs. A 6*ecutwfc~10*ecutwfc value is considered as a safe~good one in the > case of ultrasoft PPs > > HTH > > Giuseppe > > -- > ******************************************************** > - 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://www.democritos.it/mailman/listinfo/pw_forum > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120328/66e01065/attachment-0001.htm
