Reversibility and mechanism in a single-crystal phase transformation

Abstract

Optical and x-ray diffraction studies of p-di-iodobenzene single crystals undergoing polymorphic phase transformation are strongly indicative of the existence of heterophase domains at temperatures well away from the classical phase equilibrium temperature. Domains of either polymorphic form can exist in a crystal of the other form. These domains seem to have a significant effect on the course of the transformation. Annealing the crystals at temperatures far from the transformation temperatures diminishes or eliminates these domains.