Lattice dynamics of the ordered vacancy compound HgIn₂Square Operator Te₄

Abstract

HgIn2 Square Operator Te4 has a structure which may be regarded as being derived from that of zincblende by the incorporation of an ordered array of vacancies. The k=0 vibrational modes of this compound have been studied using infrared reflectivity and Raman scattering measurements, the latter using Brewster-angle geometry. A semi-empirical theoretical model of the Keating type achieves a reasonable fit to the observed mode frequencies as well as the elastic constant data of Saunders and Seddon (1970) and is used to predict dispersion relations. Qualitative features of the spectrum related to the role of the vacancy are discussed.