Twinning by inversion
From Online Dictionary of Crystallography
Maclage par inversion (Fr). Inversionsverzwilligung (Ge). Geminazione per inversione (It). 反転双晶化 (Ja).
Definition
The symmetry operation relating pairs of domain structures twinned by inversion may be represented by inversion through a point or by some other isometry equivalent to inversion under the point symmetry group of the domain structure. A two-domain-structure twin that is twinned by inversion is called an inversion twin, but this term is not appropriate when there are more than two domain structures. Twinning by inversion can only occur in non-centrosymmetric structures.
See also
Section 1.3 of International Tables of Crystallography, Volume C
Section 3.3 of International Tables of Crystallography, Volume D