So let's take a hexagonal crystal. The term:(adsbygoogle = window.adsbygoogle || []).push({});

C_{6}then refers to the 6-fold rotation group. I litterarily have no idea about what a group is but still want to understand the basic things qualitatively.

So what is meant by the 6-fold rotation group? Is it the set of 6 fold rotations leaving the crystal invariant. How many members are there in the case of the 2d and 3d hexagonal lattice?

Combination of symmetry operations are also considered. For example:

C_{6h}is the 6 fold rotation group plus the addition of a horizontal reflection plane. In this case, what specifies the position of this plane other than it being perpendicular to the rotation axis?

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# Understanding the schoenflies notation

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