[cctbxbb] Introducing arbitrary translations in symmetry operations

Ralf W. Grosse-Kunstleve rwgk at yahoo.com
Wed Jun 1 22:32:08 PDT 2011

Hi Emre,

>We are trying to identify affine normalizers' space group from the additional operators, but having difficulties in introducing the arbitrary translations.
>As an example, suppose that our "base" space group is 25, and the additional operators are:
>which, combined, defines P1 mmm
>But we couldn't find a way to introduce "x,y,z+t" while we are "expand_smx"ing the space group with these operators.

The space_group class only supports finite groups (and only in settings
that can be represented with integral rotation parts and rational
translation parts).
We have the class cctbx.sgtbx.search_symmetry, which multiplies the
discrete origin shifts into the space group and keeps track
of the continuous allowed origin shifts separately.

It would need new code to determine a full description of affine
normalizers. (Are they considered space groups?)


More information about the cctbxbb mailing list