Peculiarities of the lattice dynamics of cubic mercury chalcogenides

The lattice dynamics of cubic mercury chalcogenides (HgTe, HgSe, beta-HgS) was investigated by IR reflectivity, Raman scattering and inelastic neutron scattering measurements. The important role of two-phonon Raman scattering related to TA. excitations was confirmed for HgSe and beta-HgS and explain ed by the particular TA dispersion for mercury compounds. Analysis of the o ptical spectra taken for HgSe demonstrates that the resonant two-phonon dif ference process (widely accepted for HgTe, HgSe and the mixed crystals grow n on the basis of these compounds) is not able to explain the present exper imental data.