Observation of pressure-induced disproportionation reaction of LaH using vibrational spectroscopies

振動分光法によるLaHの圧力誘起不均化反応の観測

櫻井 陽子; 町田 晃彦; 青木 勝敏

Sakurai, Yoko; Machida, Akihiko; Aoki, Katsutoshi

Pressure-induced disproportionation reaction of LaH was investigated by infrared reflection and Raman measurements at ambient temperature. The IR reflection intensity of high wavenumber region decreased significantly beyond 12 GPa. Absorption peaks appeared at pressure above 14 GPa, being assigned to the hydrogen vibrations in tetrahedral and octahedral sites of fcc metal lattice. The peak frequencies measured in a 14-30 GPa range agreed well with those of LaH. Besides the infrared peak, a Raman peak related to the hydrogen vibration in octahedral site appeared around 700 cm above 20 GPa, which became Raman active probably due to the lattice distortion. These results indicate the precipitation of insulator LaH from metallic LaH.