Cell Symmetry

The symmetry of the cell is represented as a series of symmetry operations under which the unit cell is invariant. Each operation is represented as a $3\times3$ array.

If no symmetry is specified in the cell definition file, the default is for no symmetry to be applied.

%BLOCK SYMMETRY_OPS

$$\begin{array}{ccc} R_{11} & R_{21} & R_{31} \\ R_{12} & R_{... ...R_{13} & R_{23} & R_{33} \\ T_1 & T_2 & T_3 \vdots \end{array}$$

%ENDBLOCK SYMMETRY_OPS

Each of the first three lines contains 3 entries representing a row of a $3\times3$ array. These represent one symmetry rotation. The three entries on the following line contain the translation associated with this rotation.

SYMMETRY_GENERATE

If this keyword is persent in the cell, the highest symmetry group that applies to the structure of the cell will be found and the corresponding symmetry operations generated.

SYMMETRY_TOL $R$ [units]

This parameter is the tolerance within which symmetry will be considered to be satisfied. If an ion is found within this distance of its symmetric position, the symmetry will be considered to be satisfied.

[units] specifies the units in which the tolerance is defined. If not present, the default is Å.