# Twinning (endemic conditions of)

### From Online Dictionary of Crystallography

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When a lattice necessarily contains at least one sublattice that supports either [[twinning by reticular merohedry]] or [[twinning by reticular pseudomerohedry]], it is said that an endemic condition of [[twinning]] does exist. The following cases are known. | When a lattice necessarily contains at least one sublattice that supports either [[twinning by reticular merohedry]] or [[twinning by reticular pseudomerohedry]], it is said that an endemic condition of [[twinning]] does exist. The following cases are known. |

## Revision as of 15:26, 12 May 2006

Geminazione (condizioni endemiche di) (*It*)

When a lattice necessarily contains at least one sublattice that supports either twinning by reticular merohedry or twinning by reticular pseudomerohedry, it is said that an endemic condition of twinning does exist. The following cases are known.

**Rhombohedral lattice** (*hR*)

A *hR* lattice (symmetry *m*) always contains a *hP* lattice (symmetry 6/*mmm*). Consequently, the crystal structures based on an *R* lattice are endemic candidates to twinning by reticular merohedry via the symmetry elements that occur in the 6/*mmm* point group of the sublattice, but not in the *m* point group of the lattice.

**Cubic lattices**