Lattice parameter changes on disordering intermetallics

Most intermetallic compounds have long-range atomic (chemical) order. This can sometimes be destroyed, in some instances by quenching from a high temperature, in others by mechanical milling or irradiation. The destruction of the superlattice is normally accompanied by an increase in lattice parameter. This paper addresses the question whether this lattice parameter increase for binary intermetallic compounds is better correlated with the ordering energy or with the radius mismatch of the constituent atoms; the available evidence is surveyed. That evidence suggests that the ordering energy is the more significant variable, and this can be interpreted in terms of bond shortening associated with strong "unlike" bonds when an intermetallic acquires long-range order. (C) 1999 Elsevier Science Ltd. All rights reserved.