View source for Twinning (endemic conditions of)

<Font color="black"> Geminazione (condizioni endemiche di) </Font>(''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 <math> \bar 3</math>''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 <math> \bar 3</math>''m'' point group of the lattice.


'''Cubic lattices'''