Lattice parameter and volume changes on disordering

Lattice parameter (volume) changes consequent on disordering the L12 and B2/DO3 structures have been examined from the point of view of size mismatch of the constituent atoms and the ordering energy. No general correlation with either the atomic mismatch as judged by the realistic size of atoms or the ordering energy as suggested earlier seems to exist. The lattice parameter (volume) changes when the electropositive constituent is a transition metal behave in a very erratic fashion; this is attributed to the strong sensitivity of d electrons to their environment, leading to changes in s–d hybridization. When the electropositive constituent is a simple metal the volume increase on disordering shows strong correlation with the volume of formation of the ordered structure.