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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

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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 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

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