Author Topic: Decreasing number of bands in bandstructure  (Read 703 times)

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Offline Manish95

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Re: Decreasing number of bands in bandstructure
« Reply #15 on: September 10, 2018, 06:19 »
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.

Offline Petr Khomyakov

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Re: Decreasing number of bands in bandstructure
« Reply #16 on: September 10, 2018, 09:11 »
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?

Offline Manish95

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Re: Decreasing number of bands in bandstructure
« Reply #17 on: September 10, 2018, 09:16 »
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

Offline Petr Khomyakov

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Re: Decreasing number of bands in bandstructure
« Reply #18 on: September 10, 2018, 10:01 »
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.

Offline Manish95

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Re: Decreasing number of bands in bandstructure
« Reply #19 on: September 10, 2018, 10:11 »
Yes I took the unit cell parameters from the database

Offline Petr Khomyakov

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Re: Decreasing number of bands in bandstructure
« Reply #20 on: September 10, 2018, 11:15 »
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.
« Last Edit: September 10, 2018, 14:26 by Petr Khomyakov »

Offline Manish95

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Re: Decreasing number of bands in bandstructure
« Reply #21 on: September 18, 2018, 08:11 »
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?
« Last Edit: September 18, 2018, 08:31 by Manish95 »

Offline Petr Khomyakov

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Re: Decreasing number of bands in bandstructure
« Reply #22 on: September 21, 2018, 16:33 »
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.

Offline Manish95

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Re: Decreasing number of bands in bandstructure
« Reply #23 on: September 21, 2018, 19:56 »
I changed the unit cell to hexagonal and the problem was resolved. Thanks !!

Offline Petr Khomyakov

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Re: Decreasing number of bands in bandstructure
« Reply #24 on: September 25, 2018, 09:43 »
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.