[Pw_forum] Question about the band symmetry analysis in space group P63/mmc
Paolo Giannozzi
p.giannozzi at gmail.com
Thu May 26 07:35:51 CEST 2016
On Thu, May 26, 2016 at 12:43 AM, Qihang Liu <qihang.liu85 at gmail.com> wrote:
>
> if one forces the use_all_frac to be true he will get a imperfect
> non-symmophic operation, the result is some of the representation of a
> certain band cannot be defined, indicated with a "?".
>
well, it's not the symmetry operation that is imperfect: it is the
algorithm that finds the representations that is imperfect, in my opinion.
Symmetries exist in nature, FFT grids exist only in computer codes.
Paolo
> So the better way is to change nr1-nr3 to even numbers so that the code
> will not have any trouble on non-symmophic operations and provide the group
> representations you want.
>
> If there is anything wrong please correct me. Thanks.
>
> Best,
>
>
> Qihang Liu
>
> Research Associate
> Renewable and Sustainable Energy Institute (RASEI)
> University of Colorado Boulder
> Boulder, CO 80309-029 USA
> https://www.colorado.edu/zunger-materials-by-design/qihang-liu
>
> On Wed, May 25, 2016 at 2:29 PM, Paolo Giannozzi <p.giannozzi at gmail.com>
> wrote:
>
>> This is what I get with your input:
>>
>> 12 Sym. Ops., with inversion, found
>> (note: 12 additional sym.ops. were found but ignored
>> their fractional translations are incommensurate with FFT grid)
>>
>> while with option "use_all_frac=.true.", or by setting the FFT grid to
>> nr1=50, nr2=50, nr3=80:
>>
>> 24 Sym. Ops., with inversion, found (12 have fractional translation)
>>
>> Paolo
>>
>> On Wed, May 25, 2016 at 8:36 PM, Qihang Liu <qihang.liu85 at gmail.com>
>> wrote:
>>
>>> Dear all,
>>>
>>> I am struggling with the band symmetry analysis on a structure with a
>>> space group #194 P63/mmc (D_6h^4). I use the tag space_group to define it
>>> so I suppose the space group can be realized correctly by pwscf. As we
>>> know, the little group of Gamma point should follow the group of the
>>> crystal structure which is also D_6h. The the output of QE is D_3d. Please
>>> see the following input and outputs:
>>>
>>> scf.in
>>> &control
>>> prefix='bulk',
>>> pseudo_dir='./'
>>> outdir = './',
>>> wf_collect = .true.,
>>> /
>>> &system
>>> ibrav= 4,
>>> celldm(1)= 8.568018, celldm(3)= 1.660013, space_group = 194
>>> nat= 3, ntyp= 3, nbnd = 48,
>>> ecutwfc = 36.0, ecutrho = 320.0,
>>> lspinorb = .true., noncolin = .true.,
>>> occupations='smearing', smearing='gaussian', degauss=0.02,
>>> /
>>> &electrons
>>> diagonalization='david',
>>> conv_thr = 1.0e-8,
>>> mixing_beta = 0.7,
>>> /
>>> ATOMIC_SPECIES
>>> Li 6.941 Li.rel-pbe-s-kjpaw_psl.0.2.1.UPF
>>> Hg 200.5 Hg.rel-pbe-dn-kjpaw_psl.0.2.2.UPF
>>> As 74.922 As.rel-pbe-n-kjpaw_psl.0.2.UPF
>>> ATOMIC_POSITIONS crystal_sg
>>> Li 0.0000000000000000 0.0000000000000000 0.0000000000000000
>>> Hg 0.3333333300000021 0.6666666699999979 0.2500000000000000
>>> As 0.6666666699999979 0.3333333300000021 0.2500000000000000
>>> K_POINTS automatic
>>> 9 9 6 0 0 0
>>>
>>> nscf.in
>>> &control
>>> calculation = 'nscf'
>>> prefix='bulk',
>>> pseudo_dir='./'
>>> outdir = './',
>>> wf_collect = .true.,
>>> /
>>> &system
>>> ibrav= 4,
>>> celldm(1)= 8.568018, celldm(3)= 1.660013, space_group = 194
>>> nat= 3, ntyp= 3, nbnd = 48,
>>> ecutwfc = 36.0, ecutrho = 320.0,
>>> lspinorb = .true., noncolin = .true.,
>>> occupations='smearing', smearing='gaussian', degauss=0.02,
>>> /
>>> &electrons
>>> diagonalization='david',
>>> conv_thr = 1.0e-8,
>>> mixing_beta = 0.7,
>>> /
>>> ATOMIC_SPECIES
>>> Li 6.941 Li.rel-pbe-s-kjpaw_psl.0.2.1.UPF
>>> Hg 200.5 Hg.rel-pbe-dn-kjpaw_psl.0.2.2.UPF
>>> As 74.922 As.rel-pbe-n-kjpaw_psl.0.2.UPF
>>> ATOMIC_POSITIONS crystal_sg
>>> Li 0.0000000000000000 0.0000000000000000 0.0000000000000000
>>> Hg 0.3333333300000021 0.6666666699999979 0.2500000000000000
>>> As 0.6666666699999979 0.3333333300000021 0.2500000000000000
>>> K_POINTS crystal_b
>>> 3
>>> 0 0 0 30 ! Gamma
>>> 0 0 0.5 30 ! A
>>> 0.5 0 0.5 1 ! L
>>>
>>> bands.in
>>> &bands
>>> prefix = 'bulk',
>>> outdir='./',
>>> filband = 'bands.dat',
>>> lsym = .true.,
>>> /
>>>
>>> Output:
>>>
>>> **************************************************************************
>>>
>>> xk=( 0.00000, 0.00000, 0.00000 )
>>>
>>> double point group D_3d (-3m)
>>> there are 12 classes and 6 irreducible representations
>>> the character table:
>>>
>>> E -E 2C3 -2C3 3C2' -3C2' i -i 2S6 -2S6 3s_v
>>> -3s_v
>>>
>>> G_4+ 2.00 -2.00 1.00 -1.00 0.00 0.00 2.00 -2.00 1.00 -1.00 0.00
>>> 0.00
>>> G_5+ 1.00 -1.00 -1.00 1.00 0.00 0.00 1.00 -1.00 -1.00 1.00 0.00
>>> 0.00
>>> G_6+ 1.00 -1.00 -1.00 1.00 0.00 0.00 1.00 -1.00 -1.00 1.00 0.00
>>> 0.00
>>> G_4- 2.00 -2.00 1.00 -1.00 0.00 0.00 -2.00 2.00 -1.00 1.00 0.00
>>> 0.00
>>> G_5- 1.00 -1.00 -1.00 1.00 0.00 0.00 -1.00 1.00 1.00 -1.00 0.00
>>> 0.00
>>> G_6- 1.00 -1.00 -1.00 1.00 0.00 0.00 -1.00 1.00 1.00 -1.00 0.00
>>> 0.00
>>>
>>> Can anyone help me to explain the inconsistency? Is is related to some
>>> non-symmophic symmetries that QE can not deal with? Thanks a lot.
>>>
>>> Best,
>>>
>>> Qihang Liu
>>>
>>> Research Associate
>>> Renewable and Sustainable Energy Institute (RASEI)
>>> University of Colorado Boulder
>>> Boulder, CO 80309-029 USA
>>> https://www.colorado.edu/zunger-materials-by-design/qihang-liu
>>>
>>>
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org
>>> http://pwscf.org/mailman/listinfo/pw_forum
>>>
>>
>>
>>
>> --
>> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
>> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
>> Phone +39-0432-558216, fax +39-0432-558222
>>
>>
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>>
>
>
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--
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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