Boron phosphide under pressure: in situ study by Raman scattering and X-ray diffraction

TL;DR

This study investigates cubic boron phosphide under high pressure using in situ X-ray diffraction and Raman scattering, determining its bulk modulus, Grüneisen parameters, and pressure effects on vibrational modes and optical properties.

Contribution

It provides the first combined experimental and theoretical analysis of boron phosphide's structural and vibrational behavior under high pressure, including new measurements of bulk modulus and Grüneisen parameters.

Findings

Bulk modulus B0 = 174 GPa determined experimentally.

Grüneisen parameters for TO and LO modes estimated as 1.16 and 1.04.

Pressure-induced change in Raman mode intensity ratios explained by electro-optical constant variations.

Abstract

Cubic boron phosphide BP has been studied in situ by X-ray diffraction and Raman scattering up to 55 GPa at 300 K in a diamond anvil cell. The bulk modulus of B0 = 174(2) GPa has been established, which is in excellent agreement with our ab initio calculations. The data on Raman shift as a function of pressure, combined with equation-of-state data, allowed us to estimate the Gr\"uneisen parameters of the TO and LO modes of zinc-blende structure, {\gamma}GTO = 1.16 and {\gamma}GLO = 1.04, just like in the case of other AIIIBV diamond-like phases, for which {\gamma}GTO > {\gamma}GLO = 1. We also established that the pressure dependence of the effective electro-optical constant {\alpha} is responsible for a strong change in relative intensities of the TO and LO modes from ITO/ILO ~0.25 at 0.1 MPa to ITO/ILO ~2.5 at 45 GPa, for which we also find excellent agreement between experiment and theory.