[Pw_forum] Question about the band symmetry analysis in space group P63/mmc
Qihang Liu
qihang.liu85 at gmail.com
Thu May 26 00:43:05 CEST 2016
Dear Paolo,
Thanks a lot for your information, it helps indeed. I would like to briefly
comment on the two solutions:
The problem is that the FFT grid doesn't have several non-symmophic
operations as the original lattice does. For example, in my case the
default nr3 is 81, so it cannot afford the screw axis operation by
translating c/2 long z axis.
So both solutions work, 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 "?".
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
>>
>>
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>> Pw_forum at pwscf.org
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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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>
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