[Pw_forum] phonon at Gamma point

Luke Thulin lukethulin at netscape.net
Mon Aug 21 14:13:35 CEST 2006


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> 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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>>>>>          
>>>>>
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>>>>        
>>>>
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>  
>
>>>>>          
>>>>>
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>>    
>>
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>>>>>
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>>>>>
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>>
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