Three-Body-Force Shell Model and the Lattice Dynamics of Magnesium Oxide

Abstract
The expression for the three-body potential in ionic solids, derived quantum mechanically by Lundqvist, has been obtained classically by assuming a deformation in the charge-density distribution due to overlap of the nearest-neighbor electron cloud. A reexamination of the effect of this potential on the lattice dynamics of ionic solids has revealed an error in the original formulation of the so-called three-body-force shell model which has now been eliminated. The application of the corrected equations to MgO, with only the oxygen ion assumed polarizable, results in disperison curves which present a good agreement with the neutron spectroscopic data.