[Pw_forum] something strange in rutile and anatase calculation

[Eyvaz Isaev]

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
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> >
> >
> >
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