Diffusion in intermetallic compounds: The ordered Cu₃Au rule, its history

Abstract

The rule states that in compounds of the form AmBn, with m/n greater than 2, the atoms of species A should diffuse considerably faster than those of B. The essay is divided into several parts, the first of which considers original expressions of the Cu3Au rule, that were neglected by the scientific community, then almost entirely concerned with compounds of the simple form AB. The second part is a description of the circumstances that led to the formulation of the rule as it became known today, together with a scrutiny of those structures in which the rule should apply. The third section constitutes a discussion of the validity of the rule as exemplified in experimental studies. The essay ends with a sketchy map of possible avenues for future investigations.