[QE-users] Bandstructure with HSE provides wrong eigenvalues
Layla Martin-Samos
lmartinsamos at gmail.com
Mon May 7 07:31:56 CEST 2018
Dear Stefan nqx in your first calc is set to 4 while it is set to 1 in the
second. Only one q for forck is most probably too scarce. It might be the
reason for the discrepancy.
cheers
Layla
2018-05-06 17:34 GMT+02:00 Dr. Thomas Brumme <thomas.brumme at uni-leipzig.de>:
> Dear Stefan,
>
> you can't calculate the band structure using a self-consistent calculation.
> This would mean that you search for the ground-state density (scf) whilst
> your integrations in k-space are done on a very sparse grid... On the other
> hand you can't calculate the band structure for hybrid functionals using
> an nscf or bands calculation - the answer was given recently by Lorenzo
> Paulatto and I cite his answer at the end of the mail - you can find it
> under the following link:
>
> https://www.mail-archive.com/users@lists.quantum-espresso.or
> g/msg33817.html
>
> I can furthermore add to Lorenzos answer that you can also get the band
> structure by interpolating the E(k) dispersion on the regular grid like it
> is done in the BoltzTraP code:
>
> https://www.imc.tuwien.ac.at//forschungsbereich_theoretische
> _chemie/forschungsgruppen/prof_dr_gkh_madsen_
> theoretical_materials_chemistry/boltztrap/
> https://www.sciencedirect.com/science/article/pii/S0010465506001305
>
> Regards
>
> Thomas
>
>
> the mail:
>
> Hello,
> The problem is quite fundamental, because in order to get the Fock
> operator at a certain k-point you need the wavefunctions on a grid that is
> commensurate with it, this can only be done self-consistently.
>
> However, there are a few things you can do.
>
> 1. I think you can add k-points to the scf calculation with weight zero,
> this is boring (you'll have to specify he grid and the path by hand) and
> very computationally expensive.
>
> 2. you can interpolate the Fock operator, this should be possible if it is
> expressed om a basis of localized wavrfunctions. There is some development
> in this direction, but I don't know if it has been implemented already by
> someone.
>
> 3. You could interpolate the wavefunctions, from Wannier functions. This
> is probably impossible in practice.
>
> 4. You can interpolate the Hamiltonian, passing through a Wannier basis
> representation. This is possible, I have done it, and I've put an example
> in the git developement branch (PP/examples/W90_open_grid_example/). But
> you need to know, or learn, how to use Wannier90 (which is a useful skill
> regardless), and to use the developement version of qe.
>
> Zitat von Stefan Seidl <Stefan.Seidl at physik.uni-regensburg.de>:
>
>
> Dear All,
>> I am calculating with QUANTUM ESPRESSO the BANDSTRUCTURE of Silicon with
>> HYBRID FUNCTIONAL HSE.
>>
>> My calculation contains 3 steps:
>>
>> 1: pw.x < si.scf.in > si.scf.out
>> 2: pw.x < si.scf_instead_bands.in >
>> si.scf_instead_bands.out
>> 3: bands.x < bands.in > bands.out
>>
>> to 1: I am using an explicit kpoint list with a correspoinding qpoint grid
>> all kpoints (12 12 12 mesh )are equal weighted with 1 (which
>> provides the weight 2/(12**3) )
>> #######################################################
>> &control
>> calculation = 'scf'
>> prefix = 'silicon',
>> pseudo_dir = './',
>> outdir = './calculation'
>> verbosity = 'high',
>> /
>> &system
>> ibrav = 2,
>> celldm(1) = 10.2612,
>> nat = 2,
>> ntyp = 1,
>> ecutwfc = 40.0,
>> ! nbnd = 8,
>> input_dft ='hse',
>> nqx1 = 4,
>> nqx2 = 4,
>> nqx3 = 4,
>> occupations = 'smearing',
>> smearing = 'gaussian',
>> degauss = 0.001,
>>
>> nosym = .TRUE.,
>> noinv = .TRUE.,
>> /
>> &electrons
>> mixing_beta = 0.7
>> /
>>
>> ATOMIC_SPECIES
>> Si 28.0855 Si_NCv0.4_PBE_stringent.upf
>> ATOMIC_POSITIONS
>> Si 0.00 0.00 0.00
>> Si 0.25 0.25 0.25
>> K_POINTS tpiba
>> 1728
>> 0.0000000 0.0000000 0.0000000 1
>> -0.0833333 0.0833333 -0.0833333 1
>> -0.1666667 0.1666667 -0.1666667 1
>> -0.2500000 0.2500000 -0.2500000 1
>> -0.3333333 0.3333333 -0.3333333 1
>> -0.4166667 0.4166667 -0.4166667 1
>> 0.5000000 -0.5000000 0.5000000 1
>> 0.4166667 -0.4166667 0.4166667 1
>> 0.3333333 -0.3333333 0.3333333 1
>> 0.2500000 -0.2500000 0.2500000 1
>> 0.1666667 -0.1666667 0.1666667 1
>> 0.0833333 -0.0833333 0.0833333 1
>> 0.0833333 0.0833333 0.0833333 1
>> 0.0000000 0.1666667 0.0000000 1
>> -0.0833333 0.2500000 -0.0833333 1
>> -0.1666667 0.3333333 -0.1666667 1
>> ...
>>
>>
>>
>>
>> to 2: here I am just specifying the special kpoint path
>> #######################################################
>>
>> &control
>> calculation = 'scf'
>> prefix = 'silicon',
>> pseudo_dir = './',
>> outdir = './calculation'
>> verbosity = 'high',
>> /
>> &system
>> ibrav = 2,
>> celldm(1) = 10.2612,
>> nat = 2,
>> ntyp = 1,
>> ecutwfc = 40.0,
>> nbnd = 8,
>> input_dft ='hse',
>> nqx1 = 1,
>> nqx2 = 1,
>> nqx3 = 1,
>> occupations = 'smearing',
>> smearing = 'gaussian',
>> degauss = 0.001,
>>
>> nosym = .TRUE.,
>> noinv = .TRUE.,
>> /
>> &electrons
>> mixing_beta = 0.7
>> /
>>
>> ATOMIC_SPECIES
>> Si 28.0855 Si_NCv0.4_PBE_stringent.upf
>> ATOMIC_POSITIONS
>> Si 0.00 0.00 0.00
>> Si 0.25 0.25 0.25
>> K_POINTS tpiba
>> 50
>> 0.50000000 0.50000000 0.50000000 1
>> 0.44444444 0.44444444 0.44444444 2
>> 0.38888889 0.38888889 0.38888889 3
>> 0.33333333 0.33333333 0.33333333 4
>> 0.27777778 0.27777778 0.27777778 5
>> 0.22222222 0.22222222 0.22222222 6
>> 0.16666667 0.16666667 0.16666667 7
>> 0.11111111 0.11111111 0.11111111 8
>> 0.05555556 0.05555556 0.05555556 9
>> 0.00000000 0.00000000 0.00000000 10
>> 0.00000000 0.00000000 0.00000000 11
>> ...
>>
>>
>>
>> The eigenvalues from my 1st calculation si.scf.out are correct !
>> But the eigenvalues of the 2nd calculation si.bands.out are wrong !
>> E.g. the HOMO-LUMO distance at the Gamma point is just too big (compared
>> to VASP results which are proven to be right)!
>>
>> Where is the mistake in my input file si.bands.in for the 2nd
>> calculation ??
>>
>> Thanks a lot, best
>> Stefan
>>
>
> --
> Dr. rer. nat. Thomas Brumme
> Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
> Leipzig University
> Phillipp-Rosenthal-Strasse 31
> 04103 Leipzig
>
> Tel: +49 (0)341 97 36456
>
> email: thomas.brumme at uni-leipzig.de
>
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