Lattice dynamics of beryllium oxide:: Inelastic x-ray scattering and ab initio calculations

The phonon-dispersion relations of the lightest wurtzite structure compound BeO have been determined from inelastic x-ray scattering (IXS) measurements and analyzed by ab initio calculations. Experimental data and calculations show good agreement and reconcile the existing controversies. The phonon linewidth of the longitudinal-optical phonon along Gamma-A reveals a marked q dependence, which can be correlated with the two-phonon density of states, thus pointing toward a strong anharmonic behavior.