GRUNEISEN-PARAMETER OF SOFT PHONONS AND HIGH-PRESSURE PHASE-TRANSITIONS IN SEMICONDUCTORS

The linear correlation between the Grüneisen parameter, 7χ, of the transverse acoustic phonon at point X in the Brillouin zone and the phase transition pressure, first noted by Weinstein in the case of a few semiconductors, is re-examined. In contrast to this observation, a simple model predicts that if there exists a correlation between these parameters, -B/γχ must vary linearly with the transition pressure, where B is the bulk modulus. The available data on various semiconductors are reanalysed based on this model; a dependence of this type is also not found. The reasons for the absence of any correlation between these parameters are discussed. © 1990.