| Autor: |
Salke NP; Center for High Pressure Science & Technology Advanced Research (HPSTAR), Beijing 100094, People's Republic of China., Davari Esfahani MM; Department of Geosciences, Center for Materials by Design and Institute for Advanced Computational Science, State University of New York, Stony Brook, New York 11794-2100, United States., Yedukondalu N; Department of Geosciences, Center for Materials by Design and Institute for Advanced Computational Science, State University of New York, Stony Brook, New York 11794-2100, United States., Zhang Y; Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, People's Republic of China., Kruglov IA; Department of Problems of Physics and Energetics, Moscow Institute of Physics and Technology, 9 Institutskiy Lane, Dolgoprudny City, Moscow Region 141700, Russia.; Dukhov Research Institute of Automatics (VNIIA), Moscow 127055, Russia., Zhou J; Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States., Greenberg E; Center for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637, United States., Prakapenka VB; Center for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637, United States., Liu J; Center for High Pressure Science & Technology Advanced Research (HPSTAR), Beijing 100094, People's Republic of China., Oganov AR; Department of Problems of Physics and Energetics, Moscow Institute of Physics and Technology, 9 Institutskiy Lane, Dolgoprudny City, Moscow Region 141700, Russia.; Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, 3 Nobel Street, Moscow 143026, Russia.; International Center for Materials Discovery, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China., Lin JF; Department of Geological Sciences, The University of Texas at Austin, Austin, Texas 78712, United States. |
| Abstrakt: |
Crystal structure prediction (CSP) methods recently proposed a series of new rare-earth (RE) hydrides at high pressures with novel crystal structures, unusual stoichiometries, and intriguing features such as high- T c superconductivity. RE trihydrides (REH 3 ) generally undergo a phase transition from ambient P 6 3 / mmc or P 3̅ c 1 to Fm 3̅ m at high pressure. This cubic REH 3 ( Fm 3̅ m ) was considered to be a precursor to further synthesize RE polyhydrides such as YH 4 , YH 6 , YH 9 , and CeH 9 with higher hydrogen contents at higher pressures. However, the structural stability and equation of state (EOS) of any of the REH 3 have not been fully investigated at sufficiently high pressures. This work presents high-pressure X-ray diffraction (XRD) measurements in a laser-heated diamond anvil cell up to 100 GPa and ab initio evolutionary CSP of stable phases of DyH 3 up to 220 GPa. Experiments observed the Fm 3̅ m phase of DyH 3 to be stable at pressures from 17 to 100 GPa and temperatures up to ∼2000 K. After complete decompression, the P 3̅ c 1 and Fm 3̅ m phases of DyH 3 recovered under ambient conditions. Our calculations predicted a series of phases for DyH 3 at high pressures with the structural phase transition sequence P 3̅ c 1 → Imm 2 → Fm 3̅ m → Pnma → P 6 3 / mmc at 11, 35, 135, and 194 GPa, respectively. The predicted P 3̅ c 1 and Fm 3̅ m phases are consistent with experimental observations. Furthermore, electronic band structure calculations were carried out for the predicted phases of DyH 3 , including the 4f states, within the DFT+U approach. The inclusion of 4f states shows significant changes in electronic properties, as more Dy d states cross the Fermi level and overlap with H 1s states. The structural phase transition from P 3̅ c 1 to Fm 3̅ m observed in DyH 3 is systematically compared with other REH 3 compounds at high pressures. The phase transition pressure in REH 3 shows an inverse relation with the ionic radius of RE atoms. |
