Space group of Monolayer MoS2

[Manish95]

Hi,

I imported the cif file for 2H MoS2 which included 1 unit cell having 2 layers of MoS2. The space group was 194. In order to make it a monolayer, I deleted the other set of atoms and just repeated my lattice in a and b directions to have a monolayer. But then the space group was changed to 187. Why is the space group changing? Does this still represent the true monolayer MoS2?

[Petr Khomyakov]

This change of the space group took place when building a MoS2 monolayer by deleting one of the two monolayers in the bulk MoS2 primitive cell. And this is because bulk MoS2 and a monolayer of MoS2 have different space group symmetries, I suppose. Otherwise, why do you think they should be the same?

You may actually take a look at this paper A. Molina-Sánchez and L. Wirtz
Phys. Rev. B 84, 155413 – Published 11 October 2011, where the space groups of the two materials are mentioned.

[Manish95]

Ok I get it why the space group changes. In the unit cell of 2H MoS2 there are 2 layers, so space group is 194 but in case of single layer we number of atoms from the unit cell are reduced and hence the space group changes, as the symmetry operations will change.

But the paper mentions space group as : P3m1 fro bulk and space group: P6m2 for monolayer. But the bulk MoS2 has P63/mmc space group. How is it different from the one reported in this paper?

[Petr Khomyakov]

This is the question to the authors. QuantumATK detects the right space group of bulk MoS2, this is what I can say, and this group is different from that of a single MoS2 monolayer, as expected.