Zone-center (<i>q</i>=0) optical phonons in CuO studied by Raman and infrared spectroscopy

Abstract

We have conducted polarized Raman and infrared-reflectance measurements on CuO single crystals. Group theory predicts nine optical vibrations, of which three (${\mathit{A}}_{\mathit{g}}$+2${\mathit{B}}_{\mathit{g}}$) are Raman active and six (3${\mathit{A}}_{\mathit{u}}$+3${\mathit{B}}_{\mathit{u}}$) are infrared active. We have observed all nine frequencies. Infrared-reflectance spectra are modeled by a modified three-parameter dielectric-function method adapted to a monoclinic crystal. The nine optical zone-center (q=0) frequencies are fitted by a lattice-dynamical model based on Wilson's FG matrix method.