Composition Plane
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Dialog Box: Composition Plane [ Composition Planes dialog]

<Standard Mode - see also Composition Plane (Cartesian)>

The composition plane may be an indexed rational plane, or it may be the rhombic section. Rhombic sections must correspond in sequence number to a twin rotation axis entered in the Twin Operator dialog. That is, if a rhombic section is the second composition plane, the second twin operator must be a twin axis to which this rhombic section is to be parallel. If the composition plane is not a rhombic section, it need not be parallel to any twin axis.

You should be aware that in rotation twins the two individuals may not match across the composition plane, even if the composition plane is parallel to the twin axis. If the composition plane is a rhombic section, it will pass through identical sections of the two crystals in terms of unit-cell geometry, but the faces may not match if they are not those of the unit cell.