Decreasing number of bands in bandstructure

[Manish95]

For a 4 x 4 supercell of mono-layer MoS2, I am unable to choose the G-M-K-G brillouin zone route. Is it because the system is now hexagonal and do I need to convert it to a rhombohedral system? The c axis is now perpendicular to the plane of MoS2.

[Petr Khomyakov]

I do not have this problem; the unit cell type should still be hexagonal for 4x4. That would not be the case you had chosen 4x5, for instance. How did you build your 4x4 unit cell?

[Manish95]

First I took 1 unit cell of MoS2. Deleted the second layer and then selected Repeat option. A: 4 and B: 4. C axis is perpendicular to monolayer MoS2 -plane

[Petr Khomyakov]

Did you take the 1x1 cell from the Database? If not, you should make sure that the 1x1 cell you are using has hexagonal unit cell type.

[Manish95]

Yes I took the unit cell parameters from the database

[Petr Khomyakov]

If you have imported the MoS2 structure from the Database by searching MoS2 and then adding it to the Stash as usual,  then you should not have this issue, at least I am not able to reproduce it in the QuantumATK 2018.06 (on Windows 10) you are using.

[Manish95]

hi,

I tried with 1 x 1 unit cell of monolayer MoS2 with 5 x 5 x 1 k point sampling. Still for band structure calculation its showing me only G, Z. I am unable to choose G-M-K-G. I found out that when I delete one of the layers of unit cell from database and do band str. calculation, I am able to see G-M-K-G. But when I stretch the uni cell along c axis to create a vacuum layer, then I see only G, Z option. How to get rid of this?

[Petr Khomyakov]

But when I stretch the uni cell along c axis to create a vacuum layer, then I see only G, Z option. How to get rid of this?

I do not have this problem. Did you increase the c-parameter in Lattice Parameters? This is what I did, and there was no change in the unit cell type. You may change the unit cell type type to hexagonal if you know that your structure is hexagonal, but as I said I am not able to reproduce your issue.

[Manish95]

I changed the unit cell to hexagonal and the problem was resolved. Thanks !!

[Petr Khomyakov]

It is good that worked, but as I said this issue is not reproducible, likely meaning that you did some modifications to the structure prior to band structure calculation, causing this change of the unit cell type from hexagonal to unit cell.