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.