[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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