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 temp erature, in others by mechanical milling or irradiation. The destruction of the superlattice is normally accompanied by an increase in lattice paramet er. This paper addresses the question whether this lattice parameter increa se for binary intermetallic compounds is better correlated with the orderin g energy or with the radius mismatch of the constituent atoms; the availabl e 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 acq uires long-range order. (C) 1999 Elsevier Science Ltd. All rights reserved.