Ferroelasticity in non-group-subgroup transitions

Abstract

Aizu's definition of ferroelasticity can be extended to transitions between two crystals whose point groups are not group-subgroup related. In general, two different variant structures then appear on both sides of the transition, each variant structure being determined by the operators “lost” at the transition. If a minimal common supergroup exists, then it is the prototype group. For each variant structure, a spontaneous strain tensor can be defined. Ferroelasticity occurs for both structures, and is termed “double ferroelasticity”, if none of the groups belong to the same symmetry system as the common minimal supergroup. Examples are discussed.

Key Words:

• Ferroelasticity
• non group-subgroup transitions