GROUP THEORY SYMBOL
GTSGGetInvSubGroup[space group, classes, basis, index]
gives an invarian subgroup of the factor group G/T (G being a space group, T the group of pure lattice translations) with a specified index
- GTSGGetInvSubGroup is mainly needed within the commands GTSGGetIreps and GTSGCharacterTable. According to an argument of Zak, every space group contains an invariant sub group of index 2 or 3. The invariant subgroup is found by taking into account the following theorem: A subgroup S of the group forms an invariant subgroup if and only ifit consists of complete classes of ).
- J. Zak, J. Math. Phys, 1, 165, (1960)
- See: W. Hergert, M. Geilhufe, Group Theory in Solid State Physics and Photonics. Problem Solving with Mathematica, chapters 3.2.2.