Lattice dynamics of NiO

The phonon dispersion curves of NiO at room temperature have been measured by inelastic neutron scattering in the symmetry directions Delta , Sigma and Lambda . The measured phonons are well reproduced within the framework of a shell model, where both ions are found to be highly polarizable. In the model, the overlap polarization is taken into account by a positive shell change of the Ni 2+ ion. The breathing deformation is found to be negligible for NiO.