[Pw_forum] phonon at Gamma point
lan haiping
lanhaiping at gmail.com
Sun Aug 20 02:47:29 CEST 2006
Dear Yansun
Thank you !
Since i just use experimental values of the lattices,
i didnot optimize the lattices and just relaxed the internal coordinates.
Should I optimize the lattices using "vc-relax" , and then run the
ph.xcalculation again ?
Regards,
Hai-Ping
On 8/20/06, Yansun Yao <yay451 at mail.usask.ca> wrote:
>
> Dear Haiping,
>
> Other than the internal coordinates, did you optimize the unit cell?
>
> Cheers
> Yansun
>
>
> Quoting lan haiping <lanhaiping at gmail.com>:
>
> > 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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