I'm confused about the crystal system of MoS2.
In the case of the monolayer MoS2, it has 3-fold rotation symmetry when viewed from the top of its unit cell (c-axis). Even in the case of bulk (AB stacking) MoS2, it has only 3-fold rotation symmetry from the same direction. So, I expected that it must be the trigonal system. However, 'Materials Projects' doesn't seem the trigonal system.
Here are some database from 'Material Projects'
List of MoS2
https://materialsproject.org/#search/materials/{%22reduced_cell_formula%22%3A%22MoS2%22}
Bulk MoS2
https://materialsproject.org/materials/mp-2815/
Bilayer MoS2
https://materialsproject.org/materials/mp-1025874/
and so on.
Some of them are the trigonal system, and the others are the hexagonal system. I studied the minimum symmetries determine the crystal system, or that is a misconception. But now, it might be wrong by the web data.
Which one is correct and if both are correct, how can I check the 6-fold rotation symmetry for the hexagonal system?
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This is the figure for the HCP structure. Its symmetry along the c-axis can be called 3/m or bar(6).
This view is the bulk MoS2 along c-axis. In the unit cell, it has two layers of MoS2. However, it has 6/mmm point group. How does this happend?... https://materialsproject.org/materials/mp-1018809/#