ORIENTATIONAL DISORDER IN PLASTIC MOLECULAR CRYSTALS - 1. GROUP THEORY AND ODIC DESCRIPTION.

Abstract

A group theory method for deriving a complete and non redundant canonical set of basis functions adapted to the description of Orientational disorder In (plastic molecular) Crystal (ODIC) is developed. The method takes full advantage of the properties of the site and molecular symmetry groups. In particular, it is shown that, when both groups contain improper rotations, the canonical basis includes functions which have not been previously considered.