Centre for Science at Extreme Conditions, School of Physics and Astronomy, The University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom.
Phys Rev Lett. 2013 Nov 22;111(21):215503. doi: 10.1103/PhysRevLett.111.215503. Epub 2013 Nov 19.
We have performed in situ synchrotron x-ray diffraction studies of the iridium-hydrogen system up to 125 GPa. At 55 GPa, a phase transition in the metal lattice from the fcc to a distorted simple cubic phase is observed. The new phase is characterized by a drastically increased volume per metal atom, indicating the formation of a metal hydride, and substantially decreased bulk modulus of 190 GPa (383 GPa for pure Ir). Ab initio calculations show that the hydrogen atoms occupy the face-centered positions in the metal matrix, making this the first known noninterstitial noble metal hydride and, with a stoichiometry of IrH(3), the one with the highest volumetric hydrogen content. Computations also reveal that several energetically competing phases exist, which can all be seen as having distorted simple cubic lattices. Slow kinetics during decomposition at pressures as low as 6 GPa suggest that this material is metastable at ambient pressure and low temperatures.
我们使用同步辐射 X 射线衍射技术对 iridium-hydrogen 体系进行了原位研究，压力最高可达 125 GPa。在 55 GPa 时，观察到金属晶格从 fcc 向畸变的简单立方相的相变。新相的每个金属原子的体积显著增加，表明形成了金属氢化物，并且体弹性模量大幅降低至 190 GPa（纯 Ir 为 383 GPa）。从头算计算表明，氢原子占据金属基质的面心位置，这使其成为已知的第一个非间隙贵金属氢化物，并且具有 IrH(3)的化学计量比，是具有最高体积氢含量的氢化物。计算还表明，存在几种能量上竞争的相，它们都可以看作具有畸变的简单立方晶格。在压力低至 6 GPa 的情况下，分解的动力学缓慢表明，在环境压力和低温下，这种材料处于亚稳状态。
