We examine in detail the effect of hydrostatic compression on anisotropic semiconductors which, at ambient conditions, are characterised by the coexistence of both weak and strong cohesive forces. We focus on elucidating the response to compression of the structural, vibrational and electronic properties in quasi-two-dimensional layered materials and quasi-molecular solids. Results for layered IV–VI semiconductors (GeS and GeSe) and members of the quasi-molecular Group-V metal triiodides AsI3 are reported. Our methodology combines X-ray powder diffraction, Raman spectroscopy and ab initio electronic structure simulations. We demonstrate that compression in this class of material leads to complex compression mechanisms favouring more isotropically bonded phases, to gradual breakdown of low-frequency rigid unit vibrations and to unusual electron charge transfer effects which are reflected in non-monotonic variations of vibrational frequencies with pressure.
Physica Status Solidi. B, Basic research 211(1), pp.365-372