Definition:
A parsable string giving one of the symmetry operations of the space group in algebraic form. If W is a matrix representation of the rotational part of the symmetry operation defined by the positions and signs of x, y and z, and w is a column of translations defined by fractions, an equivalent position X' is generated from a given position X by the equation X' = WX + w (Note: X is used to represent bold_italics_x in International Tables for Crystallography Vol. A, Part 5) When a list of symmetry operations is given, it must contain a complete set of coordinate representatives which generates all the operations of the space group by the addition of all primitive translations of the space group. Such representatives are to be found as the coordinates of the general-equivalent position in International Tables for Crystallography Vol. A (2002), to which it is necessary to add any centring translations shown above the general-equivalent position. That is to say, it is necessary to list explicitly all the symmetry operations required to generate all the atoms in the unit cell defined by the setting used. In order for the defaults to work correctly, the identity operation should have _space_group_symop_id or _symmetry_equiv_pos_site_id set to 1, and _space_group_symop_operation_xyz or _symmetry_equiv_pos_as_xyz set to x,y,z; i.e. the operation labelled 1 should be the identity operation.Example:
x,1/2-y,1/2+z | glide reflection through the plane (x,1/4,z), with glide vector (1/2)c |
May appear in list containing _space_group_symop_id
Related item: _symmetry_equiv_pos_as_xyz (alternate)
Enumeration default: x,y,z
Type: char
Category: space_group_symop
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