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

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 B-0 = 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 (EOS) data, allowed us to estimate the Gruneisen parameters of the TO and LO modes of zinc-blende structure, gamma G(TO) = 1.26 and gamma G(LO) = 1.13, just like in the case of other A(III)B(V) diamond-like phases, for which gamma G(TO) > gamma G(LO) congruent to 1. We also established that the pressure dependence of the effective electro-optical constant a is responsible for a strong change in relative intensities of the TO and LO modes from I-TO/I-LO similar to 0.25 at 0.1 MPa to I-TO/I-LO similar to 2.5 at 45 GPa, for which we also find excellent agreement between experiment and theory. (C) 2014 AIP Publishing LLC.