Raman and optical absorption studies of rare-earth hydrides under high pressure

Raman and visible absorption study were performed for YH3 and ScH3 at high pressures, in order to clarify the structural and electronic phase transitions. The Raman results of YH3 revealed the presence of an intermediate phase at 9-24 GPa between the low-pressure hexagonal and high-pressure fcc phases. The characteristic behaviour was commonly observed for vibrational properties of YH3 and ScH3, suggesting a common mechanism of the structural transformation. The results of the absorption measurements for YH3 demonstrate that the optical band gap starts to close in response to the phase transition.