Many articles say
even numbers of layers or bulk crystal MoS2 have D6h point group and odd numbers of layers (including monolayer) MoS2 have D3h point group
But whenever looking at the figure of MoS2, I can't recognize there is a symmetry representing the number '6' which means 6-fold(?). With the point group flow chart,
The final answer is C3h for the bulk MoS2.
If I included the inverse symmetry with C6 symmetry, then it would give D6h? Is the inversion symmetry necessary, then why? Especially, if you can point out the six ford axis in bulk case or two layers MoS2, please let us know.
I got the hind from the reference document that Mo has D3h and S has C3v. And these two are factor group of D6h. But I don't much know about group theory... So definitely it is not D6h?
Here the unit cell of bulk 2H-MoS2
Here the top and side view of 1H-MoS2