MgAl2O4ion positions calculated for the F43m space group

Abstract

The positional parameters of the spinel MgAl2O4 were calculated using as a basis the space group F43m. The Al3+ and O2- ion positions were varied, and the lattice energy was found for each configuration. The minimum lattice energy, summing electrostatic and repulsive energy contributions, was found to be -0.248495*10-15 J/unit cell. This minimum energy occurred for ionic positional parameters satisfying Fd3m symmetry requirements. From the variations of energy with position, as well as other experimental considerations, it still seems appropriate to consider the space group for MgAl2O4 to be F43m. The specific values for the positional parameters yielding the minimum energy thus correspond to the intersection of energy surfaces of the two groups in question.