期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 109, 期 17, 页码 6463-6466出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1118168109
关键词
calcium hydride; sodalite structure
资金
- Natural Science Foundation of China (NSFC) [11104104, 11025418, 91022029]
- China 973 Program [2011CB808200]
- Changjiang Scholar and Innovative Research Team in University [IRT1132]
- Key Laboratory of Surface Physics and Chemistry [SPC201103]
- Ministry of Education, Culture, Sports, Science and Technology of Japan [20103001-20103005]
- Grants-in-Aid for Scientific Research [20103005] Funding Source: KAKEN
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 H-2 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 H-2 of electrons donated by Ca forming an H-4 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 (T-c) of 220-235 K at 150 GPa obtained from the solution of the Eliashberg equations is the highest among all hydrides studied thus far.
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