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Bandgap underestimation problem-bulk Te
Date: 2022/04/29 06:03
Name: Maedeh   <rasekh.maede@gmail.com>

Dear OpenMX developers,
Hi,

I am working with bulk Te, and its band structure should have a very small bandgap.
However, with OpenMX calculation, I see no gap in the band structure. I blame this problem on GGA, which often underestimates the gap ( HSE functional is often a better choice but as far as I know, OpenMX does not have it). I would like to ask if you know any trick to solve this problem. I have already tried strain in the three directions, and it didn't open the gap. Applying strain in one direction opens the gap, but I don't want to break the symmetry.




calculation information:


<Definition.of.Atomic.Species
Te Te7.0-s3p2d2 Te_PBE19
Definition.of.Atomic.Species>

Atoms.Number 6
Atoms.SpeciesAndCoordinates.Unit Ang
<Atoms.SpeciesAndCoordinates
1 Te 2.2270000 1.7820726 1.9746469 8.0 8.0
2 Te 0.0000000 5.6393726 1.9746469 8.0 8.0
3 Te 4.0241890 2.8196863 3.9495308 8.0 8.0
4 Te 1.7971890 6.6769863 3.9495308 8.0 8.0
5 Te 0.0000000 0.0000000 0.0000000 8.0 8.0
6 Te 2.2270000 3.8573000 0.0000000 8.0 8.0
Atoms.SpeciesAndCoordinates>

Atoms.UnitVectors.Unit Ang
<Atoms.UnitVectors
4.4540000 0.0000000 0.0000000
0.0000000 7.7146000 0.0000000
0.0000000 0.0000000 5.9240000
Atoms.UnitVectors>

#
# SCF or Electronic System
#

scf.XcType GGA-PBE # LDA|LSDA-CA|LSDA-PW
scf.SpinPolarization NC # On|Off|NC
scf.SpinOrbit.Coupling on # On|Off, default=off
scf.ElectronicTemperature 300.0 # default=300 (K)
scf.energycutoff 220 # default=150 (Ry)
scf.maxIter 200 # default=40
scf.EigenvalueSolver band # Recursion|Cluster|Band
scf.Kgrid 7 7 7 # means 4x4x4
scf.Mixing.Type rmm-diish # Simple|Rmm-Diis|Gr-Pulay
scf.Init.Mixing.Weight 0.030 # default=0.30
scf.Min.Mixing.Weight 0.001 # default=0.001
scf.Max.Mixing.Weight 0.400 # default=0.40
scf.Kerker.factor 1.0 # default=1.0
scf.Mixing.History 14 # default=5
scf.Mixing.StartPulay 6 # default=6
scf.Mixing.EveryPulay 1 # default=5
scf.criterion 1.0e-6 # default=1.0e-6 (Hartree)


#
# Band dispersion
#

Band.dispersion on # on|off, default=off
Band.Nkpath 1
<Band.kpath
100 0.00000000000 0.0000000000 0.5000000000 0.50000000000 0.0000000000 0.5000000000 Z Ca
Band.kpath>






Best regards,
Maedeh
メンテ
Page: [1]

Re: Bandgap underestimation problem-bulk Te ( No.1 )
Date: 2022/04/29 23:32
Name: Jhon W Gonzalez

Hi Maedeh,

You could try a reduction in the electronic temperature (scf.ElectronicTemperature)
I suggest you try 50.0 K or less.

Best,

Jhon
メンテ
Re: Bandgap underestimation problem-bulk Te ( No.2 )
Date: 2022/04/30 00:24
Name: Maedeh  <rasekh.maede@gmail.com>

Dear Jhon

Thank you for your suggestion.
I tried 50 k and even 10 k, but none of them opened the gap.
I don't see any changes in the band structure with decreasing the electronic temperature.

Best
Maedeh
メンテ

Page: [1]

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