LOCAL STRUCTURES IN HIGH-PRESSURE PHASES OF V2O5

The high-pressure behavior of layered V2O5 is investigated using in si tu Raman spectroscopy in a diamond anvil cell. Upon compression, the m ode associated with the vanadyl V = O double bond at 997 cm(-1) soften s and vanishes at about 10 GPa. Above 7 GPa, additional modes appear i n the V-O stretching region, at lower wavenumbers than the V = O stret ching oscillation. Such a behavior is interpreted as a pressure-induce d five-to-six coordination change around the V5+ cations, leading to a three-dimensional V2O5 lattice. Upon decompression, intermediate phas es are recovered.