Principal Vibration Modes of the LaO-GaO Binary Glass Originated from Diverse Coordination Environments of Oxygen Atoms.

LaO-GaO binary glass exhibits unusual optical properties owing to its high oxygen polarizability and low vibration energy. These optical properties include high refractive indices and a wide transmittance range. In this study, we performed classical molecular dynamics simulations on LaO-GaO glass synthesized by an aerodynamic levitation technique. We have obtained structural models that reproduce experimental results, such as NMR, high-energy X-ray diffraction, and neutron diffraction. Based on our analysis, the structural features were clarified: 5-, 6-coordinated Ga, edge-sharing GaO-GaO polyhedral linkages, and oxygen triclusters. Additionally, the vibrational density of states was calculated by diagonalization of the dynamical matrix derived from the structural models and the results were compared with Raman scattering spectra. The mode analysis of the Raman spectra revealed that the principal bands at 650 cm were mainly attributed to the stretching modes of the bridging and nonbridging oxygens. Meanwhile, the shoulder bands at the highest frequency of 750 cm were mainly attributed to the stretching modes of the bridging oxygens and oxygen triclusters. The structural models obtained in this study well describe the characteristic local structures and vibrational properties of the LaO-GaO glass.