A polarizable point ion model for partially covalent semiconductors

Theoretical models of the lattice dynamics of sapphire (α — Al₂O₃), based on the assumption of rigid ions, have been fitted to measured phonons at theΓ-point of the Brillouin zone. Short range interactions were taken into account by assuming 2-body interactions between touching ions. Additional 3-body interactions could not improve the fit significantly. Calculated dispersion curves are presented and compared with inelastic neutron scattering data. A good agreement for branches along the trigonal axis can be stated.