[Pw_forum] phonon at Gamma point
Eyvaz Isaev
eyvaz_isaev at yahoo.com
Sun Aug 20 16:59:55 CEST 2006
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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