  We report ab initio calculations of the electronic band structure and the
phonon dispersion relations of the zincblende-type mercury chalcogenides
(beta-HgS, HgSe, and HgTe). The latter have been used to evaluate the
temperature dependence of the specific heat which has been compared with
experimental data. The electronic band structure of these materials has been
confirmed to have an inverted direct gap of the alpha-tin type, which makes
HgSe and HgTe semimetallic. For beta-HgS, however, our calculations predict a
negative spin-orbit splitting which restores semiconducting properties to the
material in spite of the inverted gap. We have calculated the spin-orbit
induced linear terms in k which appear at the Gamma_8 valence bands. We have
also investigated the pressure dependence of the crystal structure and the
phonons.
