There are many alternate origins for different space groups..
However a somewhat arbitrary choice or origin was made for the first
listing of independent space groups, and it is simplest to accept the
established conventions.
If you shift the C2 origin from 0 0 0 to 1/4, 0 0 you generate C21
Just shift the origin in the C2 group and you get C21. Since they're
redundant, only one is named, the simpler one.
On Tue, 11 Sep 2007, wu donghui wrote:
Dear all,
I just get into touch with x-ray crystallography, and I made a "big"
discovery that there is no C21 space group in monoclinic s
Dear all,
I just get into touch with x-ray crystallography, and I made a "big"
discovery that there is no C21 space group in monoclinic system, which
system only contains P2, P21 and C2 groups. Even in the entire 65 chiral
space group, there is no space for this group. I made an assumption that i
