Superconductive sodalite-like clathrate calcium hydride at high pressures
Superconductive sodalite-like clathrate calcium hydride at high pressures
复制标题
高压下超导类方钠石笼形氢化钙
DOI：
10.1073/pnas.1118168109
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发表时间：
2012-04-24
影响因子：
11.1
通讯作者：
Ma, Yanming
中科院分区：
文献类型：
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作者：
Wang, Hui;Tse, John S.;Ma, Yanming
富氢化合物有望成为高压下的高温超导体。目前实现高压超导的理论氢化物结构主要由H2碎片组成。通过对不同含氢量的Ca氢化物进行粒子游优化结构搜索的系统研究，我们发现在CaH6的化学计量学中，含有氢的体心立方结构在压力150 GPa以上稳定形成含有包合Ca的特殊的“钠盐”笼。这种结构的稳定性来自于Ca提供的两个H2电子被接受，形成一个“H4”单元，作为构建三维钠盐笼的积木。这种独特的结构部分占据了区中心的简并轨道。由此产生的动态Jahn-Teller效应有助于增强电子-声子耦合并导致CaH6的超导性。由Eliashberg方程解得到的超导临界温度（Tc）为220-235 K， 150 GPa，是迄今为止所研究的所有氢化物中最高的。
Hydrogen-rich compounds hold promise as high-temperature superconductors under high pressures. Recent theoretical hydride structures on achieving high-pressure superconductivity are composed mainly of H2 fragments. Through a systematic investigation of Ca hydrides with different hydrogen contents using particle-swam optimization structural search, we show that in the stoichiometry CaH6 a body-centered cubic structure with hydrogen that forms unusual “sodalite” cages containing enclathrated Ca stabilizes above pressure 150 GPa. The stability of this structure is derived from the acceptance by two H2 of electrons donated by Ca forming an “H4” unit as the building block in the construction of the three-dimensional sodalite cage. This unique structure has a partial occupation of the degenerated orbitals at the zone center. The resultant dynamic Jahn–Teller effect helps to enhance electron–phonon coupling and leads to superconductivity of CaH6. A superconducting critical temperature (Tc) of 220–235 K at 150 GPa obtained from the solution of the Eliashberg equations is the highest among all hydrides studied thus far.