Vibrational spectroscopy at high pressure: Part 53. Alkali metavanadates and copper metagermanate

Essentially complete Raman and infrared spectra at ambient and 80 K have been obtained for the isostructural metavanadates AVO₃, (A  K, Rb, Cs). An assignment is offered on the basis of line and factor group analyses. A similar study has been made on CuGeO₃. Under pressure up to 100 kbar both KVO₃ and RbVO₃ show a single phase transition, at 56 and 53 kbar. The remarkable insensitivity of the transition pressure to change of cation implies that the major effect of pressure is chain torsion and repacking, driven by the need to reduce the cation coordination number.