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 if there is C21 space group in monoclinic system, then the four equivalent point position could be described as: x, y, z; 1/2+x, 1/2+y, z; -x, 1/2+y, -z; 1/2-x, y, -z. However when I check the 65 chiral space group, no one is compatible with this equivalent positions. And I know I must make some mistakes. Unfortunately I can not find where the mistake stems from. I have to recourse to our expert community for your generous help. All replies are warmly welcomed and appreciated.
Best regards, Donghui
