Lattice dynamics and optical properties of yttrium oxysulfide

Lattice dynamics and optical properties of yttrium oxysulfide have been investigated with the combination of microscopic Raman scattering experiment and first-principles calculation. The Raman scattering experiment on our single crystals ensures an earlier Raman spectrum based on powdered samples. Ab initio calculation based on density-functional perturbation theory is performed to obtain the phonon modes in the first Brillouin zone, dielectric and Born effective charge tensors in the uniaxial crystal structure. A rigorous assignment of all the phonon modes at F-point is achieved, in agreement with the previous and present Raman experimental data. The calculated results also indicate the ambiguity of infra-red experimental results on oxysulfides. Since these physical values are related to the properties of polaron, our theoretical approach may be useful to understand optoelectronic processes such as scintillation. (C) 2003 Elsevier Science B.V. All rights reserved.