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and TiH
up to 21 GPa by incoherent inelastic neutron scatteringHattori, Takanori; Nakamura, Mitsutaka; Iida, Kazuki*; Machida, Akihiko*; Sano, Asami; Machida, Shinichi*; Arima, Hiroshi*; Oshita, Hidetoshi*; Honda, Takashi*; Ikeda, Kazutaka*; et al.
no journal, ,
Hydrogen vibration excitations of fluorite-type ZrH and TiH were investigated up to 21 GPa and 4 GPa, respectively, by incoherent inelastic neutron scattering experiments. The first excitation energies increased with pressure, as described by the equations 
(meV) = 141.4(2) + 1.02(2)
(GPa) and (meV) = 149.4(1) + 1.21(8)(GPa) for ZrH and TiH, respectively. Coupling with pressure dependence of lattice parameters, the relations between metal-hydrogen distance (
) and are found to be well described by the equations (meV) = 1.62(9)
10
(
(meV) = 1.47(21) 10 
(AA), respectively. The slopes of these curves are much steep compared to the previously reported trend in various fluorite-type metal hydrides at ambient pressure. The hydrogen wave function spreading showed that the local potential field for a hydrogen atom shrinks more intensively than the tetrahedral site. These behaviors are likely caused by the rigid metal ion core and the resulting confinement of the hydrogen atom in the narrower potential field at high pressures.
Hattori, Takanori; Sano, Asami; Machida, Shinichi*; Abe, Jun*; Nakamura, Mitsutaka; Kawamura, Seiko
no journal, ,
Since the MLF and high-pressure PLANET beamline began operations in 2008 and 2013, respectively, we have expanded the capabilities of high-pressure neutron experiments. In this presentation, developments of diffraction technique at PLANET and those of inelastic scattering at other beamlines will be introduced along with the recent scientific results.
Sano, Asami; Kobayashi, Hiroki*; Komatsu, Kazuki*; Kagi, Hiroyuki*; Ohira, Itaru*; Kakizawa, Sho*
no journal, ,
Ice is a key component of icy planets and moons, and its behavior at high pressure and high temperature is crucial for understanding planetary interiors. Under such conditions, hydrogen mobility increases, and superionic ice phases have been predicted, where hydrogen diffuses through a static oxygen lattice. Previous X-ray studies suggested a first-order transition of ice VII at pressures above 15 GPa and around 900-1000 K. In this study, we carried out in-situ high-pressure and high-temperature neutron diffraction experiments at PLANET, J-PARC, using the multi-anvil press ATSUHIME' with D
O samples. Measurements were performed up to 
20 GPa and high temperatures. Structural changes consistent with earlier predictions were observed, though the stability field and detailed behavior appear to differ somewhat from previous reports. A more comprehensive analysis will be presented at the conference.