Dear sir, thank you for your time. Now I'm more clear about the matter.
best wishes, vega ================================================================================= Vega Lew (weijia liu) PH.D Candidate in Chemical Engineering State Key Laboratory of Materials-oriented Chemical Engineering College of Chemistry and Chemical Engineering Nanjing University of Technology, 210009, Nanjing, Jiangsu, China -------------------------------------------------- From: "Eyvaz Isaev" <[email protected]> Sent: Friday, August 29, 2008 11:23 PM To: "PWSCF Forum" <pw_forum at pwscf.org> Subject: Re: [Pw_forum] something strange in rutile and anatase calculation > Dear Vega, > > --- On Fri, 8/29/08, vega <vegalew at hotmail.com> wrote: > >> How could you get the relationship between the free >> energy and volume? Do you mean that you changed the >> cell volume sequentially and make a scf >> calculation to gain the free energies for the certain >> volume? the cell volume was grown bit by bit as >> your will, then the scf calculation did accordingly? >> > > We calculated total energy and phonons (then free energy) for a given set > of volumes. > >> and how could you get the volume as a function of > pressure as fig.2 >> shown? >> what kind of QE calculation could deal with it? >> > If you set up tstress=.true. you can find what is a stress (and pressure) > in your system. Again, for a given set of the unit cell volumes. Sometime > only a SCF calculation is enough, but sometime, especially for non-cubic > systems, you can fix pressure and relax your system. > > Bests, > Eyvaz. > >> vega >> >> -------------------------------------------------- >> From: "Eyvaz Isaev" <eyvaz_isaev at yahoo.com> >> Sent: Friday, August 29, 2008 9:00 PM >> To: "PWSCF Forum" <pw_forum at pwscf.org> >> Subject: Re: [Pw_forum] something strange in rutile and >> anatase calculation >> >> > Dear Vega, >> > >> >> > On the left side (under pressure) first DHCP has the >> lowest energy, then >> > hcp, and finally, FCC phase is the lowest in energy. >> So, we stated, there >> > are DHCP --> HCP and HCP --> FCC phase >> transitons >> > >> > Hope this helps. >> > >> > 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, vega <vegalew at hotmail.com> >> wrote: >> > >> >> From: vega <vegalew at hotmail.com> >> >> Subject: Re: [Pw_forum] something strange in >> rutile and anatase >> >> calculation >> >> To: eyvaz_isaev at yahoo.com, "PWSCF Forum" >> <pw_forum at pwscf.org> >> >> Date: Thursday, August 28, 2008, 6:05 PM >> >> Dear Eyvaz, >> >> >> >> I have read your PNAS paper just now. I'm very >> >> interesting about the phase >> >> transition mentioned in your paper. But because of >> lack of >> >> experience in >> >> your scopes, I'm not very clear about the >> detail of the >> >> calculations of >> >> phase transitions. >> >> In the second paragraph of Results and Discussion >> section, >> >> you said >> >> 'According to >> >> our free-energy calculations, there exist two >> phase >> >> transitions in the FeH >> >> system...'. How did you simulated the two >> phase >> >> transitions? How could you >> >> calculate the Volume as a function of Pressure as >> shown in >> >> Fig. 2? The line >> >> in Fig. 2 went quite smoothly, so you may not plot >> it point >> >> by point. How >> >> could you get the line? >> >> >> >> thank you for reading >> >> >> >> vega >> >> >> >> >> >> -------------------------------------------------- >> >> From: "Eyvaz Isaev" >> <eyvaz_isaev at yahoo.com> >> >> Sent: Thursday, August 28, 2008 9:25 PM >> >> To: "PWSCF Forum" >> <pw_forum at pwscf.org> >> >> Subject: Re: [Pw_forum] something strange in >> rutile and >> >> anatase calculation >> >> >> >> > Dear Vega, >> >> > >> >> > Please be not so official. I add >> (automatically) my >> >> affiliation due to our >> >> > accepted Netetiquette. >> >> > >> >> > 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, vega >> <vegalew at hotmail.com> >> >> wrote: >> >> > >> >> >> From: vega <vegalew at hotmail.com> >> >> >> Subject: Re: [Pw_forum] something strange >> in >> >> rutile and anatase >> >> >> calculation >> >> >> To: eyvaz_isaev at yahoo.com, "PWSCF >> Forum" >> >> <pw_forum at pwscf.org> >> >> >> Date: Thursday, August 28, 2008, 5:08 PM >> >> >> 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_isaev at 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 >> >> >> > >> >> >> >> _______________________________________________ >> >> >> 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 >> >> > >> >> _______________________________________________ >> >> 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 >> > >> _______________________________________________ >> 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 >
