QuantumATK Forum
QuantumATK => General Questions and Answers => Topic started by: ams_nanolab on February 6, 2013, 11:53
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Dear Sir,
We recently upgraded our ATK to 12.8 version. While running Ext Huckel simulations for monolayer MoS2, I noticed that the band diagram is not accurate. It is showing monolayer MoS2 as an indirect gap material, whereas it should be direct. I checked with the bulk-configuration from an old nc file from a previous version 11.8.2, it is showing perfectly accurate bandstructure.
Is this some bug? or some error in the new database?
Attached are the bandstructures.
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The thing which immediately comes to mind is that we changed the Huckel model to be non-selfconsistent by default. You could look into that. The parameters are unchanged.
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I am using SCF iterations in all my calculations, with Cerda Mo and Hoffman S basis.
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Need to see input files to spot any differences...
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I am using SCF iterations in all my calculations, with Cerda Mo and Hoffman S basis.
Hi,
I think you need to relax the MoS2 monolayer before band structure calculation. I have met the same problem as yours before: I calculated (by vasp) the band structure with the model extracted from the ATK 12.8 database without relaxation. It showed an indirect gap(GAMMA-K). But after relaxation (fixing cell size as that in the database & optimizing the atomic positions), the gap became direct at the high symmetry point K.
baizq
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Yup. I think that's the case.