Thank you for Prof. Eyvaz Isaev's hints I'll read the excellent article as your suggestion. It's really nice of you.
vega -------------------------------------------------- From: "Eyvaz Isaev" <eyvaz_is...@yahoo.com> Sent: Thursday, August 28, 2008 8:58 PM To: "PWSCF Forum" <pw_forum at pwscf.org> Subject: Re: [Pw_forum] something strange in rutile and anatase calculation > Hi, > > One more suggestion. > As far as I know the same situation is for \alpha and \omega phases of Ti, > as well as HCP and DHCP phases of FeH. But free energy calculations have > shown than \alpha-Ti and DHCP FeH are stabilized due to the phonon > contribution. > For FeH you can see: Eyvaz I. Isaev et al., Dynamical stability of Fe-H in > the Earth's mantle and core regions, Proceedings of the National Academy > of Sciences of the USA (PNAS), 104 (22), 29 May 2007, 9168. PNAS Special > Issue "Geophysics". > > So, you can try follow this way, if you like. > > Bests, > Eyvaz. > > > ------------------------------------------------------------------- > Prof. Eyvaz Isaev, > Theoretical Physics Department, Moscow State Institute of Steel & Alloys, > Russia, > Department of Physics, Chemistry, and Biology (IFM), Linkoping University, > Sweden > Condensed Matter Theory Group, Uppsala University, Sweden > Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com > > > --- On Thu, 8/28/08, Nicola Marzari <marzari at MIT.EDU> wrote: > >> From: Nicola Marzari <marzari at MIT.EDU> >> Subject: Re: [Pw_forum] something strange in rutile and anatase >> calculation >> To: "PWSCF Forum" <pw_forum at pwscf.org> >> Date: Thursday, August 28, 2008, 3:01 PM >> vega wrote: >> > Dear all, >> > >> > It is known that the rutile is more stable than >> anatase in >> > thermodynamics. Surprisingly, when I did the vc-relax >> calculation by >> > QE, I found the calculated energy of anatase lower >> than rutile. Both >> > vc-relax calculation for rutile and anatase onverged >> in 6 scf cycles and >> > 3 bfgs steps, giving the final enthalpy = >> -362.7585836890 Ry for rutile >> > and -725.5447425835 Ry for antase. So the average >> energy of [TiO2] unit >> > is -181.3792918445 Ry for rutile and -181.386185645875 >> Ry for anatase. >> > It looks like anatase is more stable than rutile. Do >> you think it was >> > quite strange? >> >> >> Dear Vega, >> >> your results are probably correct. It's a known failure >> of LDA and GGA >> to stabilize anatase more than rutile. >> >> nicola >> >> -- >> --------------------------------------------------------------------- >> Prof Nicola Marzari Department of Materials Science and >> Engineering >> 13-5066 MIT 77 Massachusetts Avenue Cambridge MA >> 02139-4307 USA >> tel 617.4522758 fax 2586534 marzari at mit.edu >> http://quasiamore.mit.edu >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://www.democritos.it/mailman/listinfo/pw_forum > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >