We report the results of ab initio total-energy pseudopotential calculations, high-pressure angle-dispersive powder x-ray diffraction, and vibrational spectroscopy measurements on the IV-VI layered semiconductor germanium selenide (GeSe). The calculated hydrostatic pressure dependence of the crystal structure is found to be in good agreement with the results of high-resolution x-ray structural studies. In contrast to previous reports, no evidence of a pressure-induced first-order structural phase transition is found up to 130 kbar. However, a metallization transition is predicted in our electronic structure calculations. This is consistent with reports of a large resistivity drop at high pressure. The rigid-layer vibrational shear mode is also investigated by ab initio methods within the rigid-layer mode approximation and the frequency is found to be in fair agreement with our Raman scattering results at ambient pressure. At higher pressures the calculated frequency is substantially overestimated in the calculations.
