[Pw_forum] phonon at Gamma point

Stefano Baroni baroni at sissa.it
Thu Aug 24 14:56:15 CEST 2006


I have an exercise for you. Try to solve yourself your problem by  
browsing the archive of this mailing list, where this very same   
question has been asked and answered several times.

Also, I would like to urge everybody here to make a serious effort to  
browse the archive _before_ posting a request. I think it is sign of  
respect for people who have already taken the time to help others,  
and will also help us being helpful to those who have problems not  
previously met by anybody.

Just as a hint: you problem has to do with non-symmorphic symmetry  
groups and with the way symmetry operations are found out in the  
code ...

Hope this helps

Stefano B.

On Aug 24, 2006, at 2:33 PM, lan haiping wrote:

>
> Dear Eyvaz :
>
> I just relaxed Anatase TiO2  with ibrav= 7 ,
> then output gave that Only 8 symmetry Operations are found.
> According  to your mail, this structure should have 16 Symmetry  
> Operations, so
> how can i obtain correct  symmetry operations ?
>
> Input file is below , thank you in advance !
>
> &CONTROL
>              title = 'TiO2' ,
>        calculation = 'relax',
>          verbosity = 'default',
>            tprnfor = .true.,
>             outdir = '/home/haiping/tmp/',
>             prefix = 'tio2-1',
>            disk_io = 'default',
>              nstep = 200,
>         pseudo_dir = '/home/haiping/espresso/pseudo/',
> /
>
> &SYSTEM
>                 ibrav= 7,
>                celldm(1)=7.1356,celldm(3)=2.51218,
>                nat = 6 ,
>               ntyp = 2 ,
>               nbnd = 30 ,
>            ecutwfc = 30.0000000000 ,
>        occupations = 'fixed' ,
>
> &ELECTRONS
>   electron_maxstep = 100,
>           conv_thr = 1.0e-09,
>        mixing_mode = 'plain' ,
>        startingpot = 'atomic' ,
>        startingwfc = 'atomic' ,
>        mixing_beta = 0.300000000 ,
>        mixing_ndim = 8,
>    diagonalization = 'david_overlap' ,
>   diago_david_ndim = 8,
> /
>
> &IONS
>              ion_dynamics = 'bfgs',
>              pot_extrapolation = 'first_order',
>              wfc_extrapolation = 'first_order',
>
> /
>
> O  15.999  O.pw91-van_ak.UPF
> Ti 47.867  Ti.pw91-nsp-van.UPF
> ATOMIC_POSITIONS angstrom
> Ti       0.000000000   0.000000000   0.000000000
> Ti       0.000000000   1.888000000   2.371500000
> O        0.000000000    0.000000000  -1.983097630
> O        0.000000000   0.000000000   1.983097630
> O        0.000000000   1.888000000   0.387796645
> O        0.000000000   1.888000000   4.355203355
> K_POINTS   automatic
> 6 6  7   0 0 0
>
>
>
> On 8/20/06, Eyvaz Isaev <eyvaz_isaev at yahoo.com> wrote:
> OK, let me hint more.
>
> Anatase has a Pearson symbol tI12 or space group
> I4_1/amd. So, ibrav should be 7, but you have chosen a
> monoclinic lattice, i.e. ibrav=14. The space group has
> 16 symmetry elements, but your choice after correcting
> ecutrho gives only 4 symmetry elements .
>
> Imagine  FCC lattice and its conventional basis
> vectors now. According to you now we have to put
> ibrav=4 or 5. But ibrav=2 for FCC lattice.
>
> In addition, I also checked your input file via
> XCrysDen before I replied previously. Yes, there is no
> problem with it, but a figure does not look like
> anatase though  you used  nonzero ibrav. XcrysDen
> usually replicates atomic positions  if  ibrav.neq.0.
> For example, if you put ibrav=0  for  FCC cell and
> specify conventional CELL_PARAMETERS you will find  a
> rhombohedron, but using ibrav=2 and  default basis
> vectors you find a cubic cell.
>
> Bests,
> Eyvaz.
>
>
> --- lan haiping <lanhaiping at gmail.com> wrote:
>
> > Dear Eyvaz,
> > Thank you.
> > I checked the strcuture again using XCRYSDEN,
> > and found no problems related to the  lattices.
> >
> > Regards,
> >
> > Hai-Ping
> >
> >
> >
> > On 8/20/06, Eyvaz Isaev <eyvaz_isaev at yahoo.com >
> > wrote:
> > >
> > > Hi,
> > >
> > > It seems your lattice choice is not correct.
> > Please
> > > have a look at
> > > http://cst-www.nrl.navy.mil/lattice/struk/c5.html
> > >
> > > Bests,
> > > Eyvaz.
> > >
> > > --- lan haiping <lanhaiping at gmail.com> wrote:
> > >
> > > > Dear All,
> > > > I also have calculated gamma phonon frequencies
> > of
> > > > anatase TiO2 .
> > > > I run ph.x caculation after relaxing the
> > structure,
> > > > but  9 of 18 frequencies
> > > > are minus.
> > > >
> > > > Would you please give me some hints and help?
> > > >
> > > > input settings are below, thank you in advance !
> > > >
> > > > *phonons of TiO2 at Gamma
> > > >  &inputph
> > > >   tr2_ph=1.0d-14,
> > > >   recover=.true.,
> > > >   epsil=.true.,
> > > >   prefix='tio2',
> > > >   fildyn='TiO2-gamma.dyn',
> > > >   outdir='/home/haiping/tmp/'
> > > >  /
> > > > 0.0 0.0 0.0*
> > > > **
> > > > *Relaxing calculation input :*
> > > > *&CONTROL
> > > >              title = 'TiO2' ,
> > > >        calculation = 'relax',
> > > >          verbosity = 'default',
> > > >            tprnfor = .true.,
> > > >             outdir = '/home/haiping/tmp/',
> > > >             prefix = 'tio2',
> > > >            disk_io = 'default',
> > > >              nstep = 200,
> > > >         pseudo_dir =
> > > > '/home/haiping/espresso/pseudo/',
> > > > /
> > > > &SYSTEM
> > > >                 ibrav= 14,
> > > >
> > > > celldm(1)=10.2856,celldm(2)=1.0,celldm(3)=1.0,
> > > >
> > > > celldm(4)=- 0.759357,celldm(5)=-0.759357,
> > > >                celldm(6)=0.518714
> > > >                nat = 6 ,
> > > >               ntyp = 2 ,
> > > >               nbnd = 30 ,
> > > >            ecutwfc = 30.0000000000,
> > > >            ecutrho = 160.000,
> > > >        occupations = 'fixed' ,
> > > > /
> > > >
> > > >
> > > > &ELECTRONS
> > > >   electron_maxstep = 100,
> > > >           conv_thr = 1.0e-07,
> > > >        mixing_mode = 'plain' ,
> > > >        startingpot = 'atomic' ,
> > > >        startingwfc = 'atomic' ,
> > > >        mixing_beta = 0.300000000,
> > > >        mixing_ndim = 8,
> > > >    diagonalization = 'david_overlap' ,
> > > >   diago_david_ndim = 8,
> > > > /
> > > >
> > > > &IONS
> > > >              ion_dynamics = 'bfgs',
> > > >              pot_extrapolation = 'first_order',
> > > >              wfc_extrapolation = 'first_order',
> > > >
> > > > /
> > > >
> > > > ATOMIC_SPECIES
> > > > O  15.999 O.pw91-van_ak.UPF
> > > > Ti 47.867  Ti.pw91-nsp-van.UPF
> > > > ATOMIC_POSITIONS crystal
> > > > Ti    0.00000   0.00000    0.00000
> > > > Ti    0.75000   0.25000   0.50000
> > > > O     0.20800   0.20800  -0.00000
> > > > O     0.95800   0.45800   0.50000
> > > > O     0.54200   0.04200   0.50000
> > > > O     0.79200   0.79200  -0.00000
> > > > K_POINTS   automatic
> > > > 6 6 7   0 0 0
> > > >
> > > > *
> > > >
> > > >
> > > > On 8/19/06, Ezad Shojaee
> > <ezadshojaee at hotmail.com>
> > > > wrote:
> > > > >
> > > > > hi
> > > > > i am trying to calculate phonon frequencies at
> > > > gamma point of
> > > > > TiO2(anatase)
> > > > > and i have relaxed the structure enough (i
> > think
> > > > )but performing PH.Xafter
> > > > > scf, 2of 18 frequencies  are minus!
> > > > > i want to know that what technical problem do
> > i
> > > > have? does anyone
> > > > > calculate
> > > > > these beore?
> > > > > any suggestion will be appreciated
> > > > >
> > > > >
> > > >
> > >
>
> --- lan haiping <lanhaiping at gmail.com> wrote:
>
> > Dear Eyvaz,
> > Thank you.
> > I checked the strcuture again using XCRYSDEN,
> > and found no problems related to the  lattices.
> >
> > Regards,
> >
> > Hai-Ping
> >
> >
> >
> > On 8/20/06, Eyvaz Isaev < eyvaz_isaev at yahoo.com>
> > wrote:
> > >
> > > Hi,
> > >
> > > It seems your lattice choice is not correct.
> > Please
> > > have a look at
> > > http://cst-www.nrl.navy.mil/lattice/struk/c5.html
> > >
> > > Bests,
> > > Eyvaz.
> > >
> > > --- lan haiping < lanhaiping at gmail.com> wrote:
> > >
> > > > Dear All,
> > > > I also have calculated gamma phonon frequencies
> > of
> > > > anatase TiO2 .
> > > > I run ph.x caculation after relaxing the
> > structure,
> > > > but  9 of 18 frequencies
> > > > are minus.
> > > >
> > > > Would you please give me some hints and help?
> > > >
> > > > input settings are below, thank you in advance !
> > > >
> > > > *phonons of TiO2 at Gamma
> > > >  &inputph
> > > >   tr2_ph=1.0d-14,
> > > >   recover=.true.,
> > > >   epsil=.true.,
> > > >   prefix='tio2',
> > > >   fildyn='TiO2-gamma.dyn',
> > > >   outdir='/home/haiping/tmp/'
> > > >  /
> > > > 0.0 0.0 0.0*
> > > > **
> > > > *Relaxing calculation input :*
> > > > *&CONTROL
> > > >              title = 'TiO2' ,
> > > >        calculation = 'relax',
> > > >          verbosity = 'default',
> > > >            tprnfor = .true.,
> > > >             outdir = '/home/haiping/tmp/',
> > > >             prefix = 'tio2',
> > > >            disk_io = 'default',
> > > >              nstep = 200,
> > > >         pseudo_dir =
> > > > '/home/haiping/espresso/pseudo/',
> > > > /
> > > > &SYSTEM
> > > >                 ibrav= 14,
> > > >
> > > > celldm(1)= 10.2856,celldm(2)=1.0,celldm(3)=1.0,
> > > >
> > > > celldm(4)=-0.759357,celldm(5)=-0.759357,
> > > >                celldm(6)=0.518714
> > > >                nat = 6 ,
> > > >               ntyp = 2 ,
> > > >               nbnd = 30 ,
> > > >            ecutwfc = 30.0000000000,
> > > >            ecutrho = 160.000,
> > > >        occupations = 'fixed' ,
> > > > /
> > > >
> > > >
> > > > &ELECTRONS
> > > >   electron_maxstep = 100,
> > > >           conv_thr = 1.0e-07,
> > > >        mixing_mode = 'plain' ,
> > > >        startingpot = 'atomic' ,
> > > >        startingwfc = 'atomic' ,
> > > >        mixing_beta = 0.300000000,
> > > >        mixing_ndim = 8,
> > > >    diagonalization = 'david_overlap' ,
> > > >   diago_david_ndim = 8,
> > > > /
> > > >
> > > > &IONS
> > > >              ion_dynamics = 'bfgs',
> > > >              pot_extrapolation = 'first_order',
> > > >              wfc_extrapolation = 'first_order',
> > > >
> > > > /
> > > >
> > > > ATOMIC_SPECIES
> > > > O  15.999 O.pw91-van_ak.UPF
> > > > Ti 47.867  Ti.pw91-nsp-van.UPF
> > > > ATOMIC_POSITIONS crystal
> > > > Ti    0.00000   0.00000   0.00000
> > > > Ti    0.75000   0.25000   0.50000
> > > > O     0.20800   0.20800  -0.00000
> > > > O     0.95800   0.45800   0.50000
> > > > O     0.54200   0.04200   0.50000
> > > > O     0.79200   0.79200  -0.00000
> > > > K_POINTS   automatic
> > > > 6 6 7   0 0 0
> > > >
> > > > *
> > > >
> > > >
> > > > On 8/19/06, Ezad Shojaee
> > <ezadshojaee at hotmail.com>
> > > > wrote:
> > > > >
> > > > > hi
> > > > > i am trying to calculate phonon frequencies at
> > > > gamma point of
> > > > > TiO2(anatase)
> > > > > and i have relaxed the structure enough (i
> > think
> > > > )but performing PH.Xafter
> > > > > scf, 2of 18 frequencies  are minus!
> > > > > i want to know that what technical problem do
> > i
> > > > have? does anyone
> > > > > calculate
> > > > > these beore?
> > > > > any suggestion will be appreciated
> > > > >
> > > > >
> > > >
> > >
> >
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
[+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

Please, if possible, don't  send me MS Word or PowerPoint attachments
Why? See:  http://www.gnu.org/philosophy/no-word-attachments.html



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