[Pw_forum] phonon at Gamma point

lan haiping lanhaiping at gmail.com
Mon Aug 21 14:52:50 CEST 2006


Thank you , Luke.
I am  calculating phonons with this settings.

Regards,
Hai-Ping


On 8/21/06, Luke Thulin <lukethulin at netscape.net> wrote:
>
>  I believe Eyvaz is correct, for anatase use:
>
> ibrav = 7
> A choice of cartesian coordinates for measured values:
> Ti (0,0,0)
> Ti (0,a/2,c/4)
> O (0,0,-uc)
> O (0,0,+uc)
> O (0,a/2,c/4-uc)
> O (0,a/2,c/4+uc)
>
> where a = 3.785, c=9.514, u=.2081
>
>
> Luke
>
> 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> <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> <eyvaz_isaev at yahoo.com>
> wrote:
>
>
> Hi,
>
> It seems your lattice choice is not correct.
>
>
> Please
>
>
> have a look athttp://cst-www.nrl.navy.mil/lattice/struk/c5.html
>
> Bests,
> Eyvaz.
>
> --- lan haiping <lanhaiping at gmail.com> <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> <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> <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> <eyvaz_isaev at yahoo.com>
> wrote:
>
>
> Hi,
>
> It seems your lattice choice is not correct.
>
>
> Please
>
>
> have a look athttp://cst-www.nrl.navy.mil/lattice/struk/c5.html
>
> Bests,
> Eyvaz.
>
> --- lan haiping <lanhaiping at gmail.com> <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> <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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