Transfer of interstitial hydrogen atoms and formation of monohydride in rare-earth metals under high pressure

Machida, Akihiko; Honda, Mitsunori   ; Hattori, Takanori   ; Sano, Asami   ; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Komatsu, Kazuki*; Arima, Hiroshi; Oshita, Hidetoshi*; Otomo, Toshiya*; Kim, D. Y.*

We have investigated the pressure-induced phase separation in rare-earth metal dihydrides by synchrotron radiation X-ray diffraction and neutron diffraction experiments. The phase separation has been observed at about 11 GPa in the lanthanum dihydride. The neutron diffraction experiments have revealed that an NaCl-type mono-deuteride is formed as a counterpart of the deuterium-rich phase. This result suggests that the three different hydrides, mono-, di-, and tri-hydrides, with the fcc metal lattice are realized. Hence, it is expected that the site-dependence of the H-M bonding nature will be able to investigate.