Re: [ccp4bb]: A question...

[Gerard Bricogne <gb10@globalphasing.com>]

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On Thu, Feb 14, 2002 at 08:17:20PM +0100, F.Xavier Gomis-Rüth wrote:
> ..... for the old hardcore crystallographers:
> What are P222, P2(1)2(1)2(1),P2(1)2(1)2, etc. to themselves ?
> Iso....   what ?
> 

     Dear Xavier,

     The answer is probably that they are 'isomorphic' to each other, in the 
     sense that their elements can be labelled in such a way that they then 
     have identical multiplication tables. A stronger relationship is that 
     they have the same underlying point group, and differ only by their 
     assignments of non-primitive translations to these point-group elements, 
     in such a way as to obey the Frobenius congruences and thus still give 
     rise to a group.
     
     I hope this is at least part of the answer you were looking for.
     
     
     With best wishes,
     
          Gerard.

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