Stability of Ar(H 2 ) 2 to 358 GPa

Autor: Cheng Ji, Wenge Yang, Dmitry Popov, Yue Meng, Rajeev Ahuja, Ho-kwang Mao, Naresh K. Jena, Vitali B. Prakapenka, Bing Li, Junyue Wang, Vivekanand Shukla, Jesse S. Smith, Alexander F. Goncharov
Rok vydání: 2017
Předmět:
Zdroj: Proceedings of the National Academy of Sciences. 114:3596-3600
ISSN: 1091-6490
0027-8424
Popis: "Chemical precompression" through introducing impurity atoms into hydrogen has been proposed as a method to facilitate metallization of hydrogen under external pressure. Here we selected Ar(H2)2, a hydrogen-rich compound with molecular hydrogen, to explore the effect of "doping" on the intermolecular interaction of H2 molecules and metallization at ultrahigh pressure. Ar(H2)2 was studied experimentally by synchrotron X-ray diffraction to 265 GPa, by Raman and optical absorption spectroscopy to 358 GPa, and theoretically using the density-functional theory. Our measurements of the optical bandgap and the vibron frequency show that Ar(H2)2 retains 2-eV bandgap and H2 molecular units up to 358 GPa. This is attributed to reduced intermolecular interactions between H2 molecules in Ar(H2)2 compared with that in solid H2 A splitting of the molecular vibron mode above 216 GPa suggests an orientational ordering transition, which is not accompanied by a change in lattice symmetry. The experimental and theoretical equations of state of Ar(H2)2 provide direct insight into the structure and bonding of this hydrogen-rich system, suggesting a negative chemical pressure on H2 molecules brought about by doping of Ar.
Databáze: OpenAIRE
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