Geometry Optimisation with CASTEP
Geometry Optimisation with CASTEP
Geometry Optimisation with CASTEP
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Next: Constraints on the cell Up: The .cell file and Previous: The k-point sampling grid<br />
Cell symmetry<br />
If the unit cell is invariant under certain symmetry operations these can be specified in the .cell file<br />
%BLOCK SYMMETRY_OPS<br />
%ENDBLOCK SYMMETRY_OPS<br />
Each symmetry operation occupies four lines. The first three lines make a 3x3 array that represent a<br />
symmetry rotation and the next line is the translation associated <strong>with</strong> this rotation.<br />
Another way is to allow <strong>CASTEP</strong> to automatically find the highest symmetry group that applies to the<br />
structure.<br />
SYMMETRY_GENERATE<br />
Note of caution; <strong>with</strong> a non-cubic cell or <strong>with</strong> a cell in which the c vector is not along the z direction the<br />
automatic symmetry generation can sometimes fail to find all of the symmetry operations that apply to a<br />
supercell.