Lattice dynamics of boron phosphide

Abstract

Using the density-functional theory, norm-conserving pseudopotentials and plane-wave expansions the authors have calculated ab initio the equation of state and the principal phonon modes in boron phosphide, including their pressure dependence and the amplitude of the eigendisplacements. Good agreement with experiment is obtained, whenever a comparison is possible: in fact, most of the results are predictions. A ten-parameter valence overlap shell model is then constructed from the available experimental data, which are completed by the data obtained in the first-principle calculations: frozen-phonon frequencies and eigenvectors. The previous speculations about the anomalous behaviour of the effective charges are discussed in the context of the present results.