Phonon Dispersion and Pressure Behavior of Hg_2Cl_2Crystals

摘要

The dispersion dependences of frequencies of acoustic and optical phonons are calcu-lated and constructed, and the density of states of the phonon spectrum is obtained for Hg_2Cl_2 crystals. The influence of the hydrostatic pressure on frequencies of acoustic and optical phonons and their dispersion is analyzed theoretically. It is revealed that an increase in the pressure leads to a considerable softening of the slowest acoustic TA branch (soft mode) at the X-point of the Brillouin zone boundary. This behavior is consistent with the phenomenological Landau theory and correlate with experiments.