Raman scattering and interaction and interference of optical vibrations in a γ-Li3PO4 superionic crystal

Abstract

Polarized Raman spectra of γ-Li3PO4 single crystal are investigated at temperatures approximately up to 700 K. It is shown that vibrations of PO4 tetrahedrons and cations of the lithium sublattice can be separated in the spectra. It is found that an increase in temperature leads to interference of one-phonon optical modes of symmetry B 2g and A g , which is accompanied by antiresonance in a frequency range near 190 cm−1. Numerical analysis of the spectrum in the region of interaction of optical modes reveals a strong temperature dependence of the interaction constant, which is determined by anharmonic coupling of optical and acoustic modes.