[Pw_forum] something strange in rutile and anatase calculation
Eyvaz Isaev
eyvaz_isaev at yahoo.com
Sat Aug 30 01:14:36 CEST 2008
Dear Wei,
Thanks a lot for bringing the paper to our attention.
I have read the paper and have 2 comments.
1. They used only norm-conserving pseudopotentials constructed by means of different methods.
2. They used only LDA, but not GGA. As it is well known (hopefully I am not wrong here) LDA fails for the ground state of Fe. In contrast to this, GGA does a good job for Fe.
So, it will be very good if Vega can calculate the total energies for the rutile and anatase phases in odrer to study whether their energy position is dependent on the choice of exchange-correlation functional.
It might also be that there is a transferability problem for these PsPs (I can not prove this, just suggestion).
It is my pleasure that they also mentioned that including of phonon contribution might be important.
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 Fri, 8/29/08, willy kohn <willykohn at gmail.com> wrote:
> From: willy kohn <willykohn at gmail.com>
> Subject: Re: [Pw_forum] something strange in rutile and anatase calculation
> To: "PWSCF Forum" <pw_forum at pwscf.org>
> Date: Friday, August 29, 2008, 10:02 PM
> Hi, Vega:
>
> A recent result (Jpn. J. Appl. Phys. 39 (2000) L847) showed
> that different
> pseudopotential leaded to different conclusions.
>
> Best,
>
> Wei
>
> On Thu, Aug 28, 2008 at 4:28 AM, vega
> <vegalew at hotmail.com> 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?
> >
> > To make the calculation both for anatase and rutile
> comparable, I used the
> > same ecutwfc=40 Ry and ecutwfc=400 Ry, and a quite
> dense k-point mesh for
> > both case, 4x4x7 for rutile and 5x5x2 for anatase.
> >
> > for better understanding in my calculation, please
> read the input file
> > below,
> > for anatase case,
> > &CONTROL
> > title = 'Anatase
> lattice' ,
> > calculation = 'vc-relax' ,
> > restart_mode = 'from_scratch'
> ,
> > outdir =
> >
> '/home/hjfeng/vega/TiO2/Anatase/lattice/vctest/tmp/'
> ,
> > wfcdir = '/tmp/' ,
> > pseudo_dir =
> '/home/hjfeng/vega/espresso-4.0/pseudo/' ,
> > prefix = 'Anatase
> lattice' ,
> > disk_io = 'none' ,
> > nstep = 1000 ,
> > /
> > &SYSTEM
> > ibrav = 6,
> > celldm(1) = 7.1356,
> > celldm(3) = 2.5122,
> > nat = 12,
> > ntyp = 2,
> > ecutwfc = 40 ,
> > ecutrho = 400 ,
> > /
> > &ELECTRONS
> >
> > /
> > &IONS
> > ion_dynamics = 'bfgs' ,
> > /
> > &CELL
> > cell_dynamics = 'bfgs' ,
> > /
> > ATOMIC_SPECIES
> > Ti 47.86700 Ti.pw91-sp-van_ak.UPF
> > O 15.99940 O.pw91-van_ak.UPF
> > ATOMIC_POSITIONS crystal
> > Ti 0.000000000 0.000000000 0.000000000
> > Ti 0.500000000 0.500000000 0.500000000
> > Ti 0.000000000 0.500000000 0.250000000
> > Ti 0.500000000 0.000000000 0.750000000
> > O 0.000000000 0.500000000 0.042000000
> > O 0.000000000 0.000000000 0.208000000
> > O 0.500000000 0.500000000 0.292000000
> > O 0.000000000 0.500000000 0.458000000
> > O 0.500000000 0.000000000 0.542000000
> > O 0.500000000 0.500000000 0.708000000
> > O 0.000000000 0.000000000 0.792000000
> > O 0.500000000 1.000000000 0.958000000
> > K_POINTS automatic
> > 5 5 2 1 1 1
> >
> > for rutile case,
> >
> > &CONTROL
> > title = Rutile_lattice ,
> > calculation = 'vc-relax' ,
> > restart_mode = 'from_scratch'
> ,
> > outdir =
> > '/home/vega32/TiO2/rutile/lattice/vcrelax/tmp'
> ,
> > wfcdir = '/tmp/' ,
> > pseudo_dir =
> '/home/vega32/espresso-4.0.1/pseudo/' ,
> > prefix = 'Anatase
> lattice' ,
> > disk_io = 'none' ,
> > nstep = 1000 ,
> > /
> > &SYSTEM
> > ibrav = 6,
> > celldm(1) = 8.6814,
> > celldm(3) = 0.6441,
> > nat = 6,
> > ntyp = 2,
> > ecutwfc = 40 ,
> > ecutrho = 400 ,
> > /
> > &ELECTRONS
> >
> > /
> > &IONS
> > ion_dynamics = 'bfgs' ,
> > /
> > &CELL
> > cell_dynamics = 'bfgs' ,
> > /
> > ATOMIC_SPECIES
> > O 15.99940 O.pw91-van_ak.UPF
> > Ti 47.90000 Ti.pw91-sp-van_ak.UPF
> > ATOMIC_POSITIONS crystal
> > O 0.304800000 0.304800000 0.000000000
> > O 0.695200000 0.695200000 0.000000000
> > O 0.195200000 0.804800000 0.500000000
> > O 0.804800000 0.195200000 0.500000000
> > Ti 0.500000000 0.500000000 0.500000000
> > Ti 0.000000000 0.000000000 0.000000000
> > K_POINTS automatic
> > 4 4 7 1 1 1
> >
> > 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
> >
> > _______________________________________________
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://www.democritos.it/mailman/listinfo/pw_forum
> >
> >
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