[Pw_forum] phonon at Gamma point
Eyvaz Isaev
eyvaz_isaev at yahoo.com
Sun Aug 20 00:30:10 CEST 2006
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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