Overbending of the longitudinal optical phonon branch in diamond as evidenced by inelastic neutron and x-ray scattering

Abstract

Overbending of the longitudinal-optical-phonon branch in diamond has been evidenced along all three principal directions by a joint inelastic neutron and x-ray experiment. The observed overbending of 1.5, 0.5, and 0.2 meV (along the Delta, Lambda, and Sigma directions, respectively) confirms previous ab initio lattice-dynamics calculations, thus providing experimental proof for the explanation of the anomalous peak in the two-phonon Raman spectrum.