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4
votes
0answers
37 views
Are chiral quasicrystals possible?
Quasicrystals are materials that have long-range atomic order but lack the translational symmetry of conventional crystals. All quasicrystalline tilings and packings I have read about thus far, whilst ...
3
votes
1answer
61 views
Are all cubic point groups encountered?
My symmetry lecture notes state that there are seven high-symmetry 3D point groups, which have more than one rotation axis of order greater than 2: $T$, $T_d$, $T_h$, $O$, $O_h$, $I$, $I_h$. I ...
3
votes
1answer
117 views
Are these two space groups in a group–subgroup relationship?
Given two crystal space groups, how can one determine if they are in a group-subgroup relationship? The specific case at hand is P 21/m 2/m 2/a (aka P m m a, #51) and P m m 2 (#25), but knowing how to ...
5
votes
2answers
544 views
How does one recognized Td/Oh symmetry in molecules?
The identification of point groups of a molecule is usually done following a strict scheme, either manually or algorithmically. In all textbooks I could find, however, the first step of the scheme is ...
2
votes
1answer
70 views
Is a 2-D periodic structure isomorphic with the surface of a torus, a sphere, neither or both?
When I was reading through the ADF-BAND tutorials, one of the toy systems presented was a 1-D periodic structure involving 3 collinear hydrogen atoms. The tutorial pointed out that, topologically ...
