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H₂ Chemical Bond in a High-Pressure Crystalline Environment.

ABSTRACT: We show that the hydrogen in metal superhydride compounds can adopt two distinct states-atomic and molecular. At low pressures, the maximum number of atomic hydrogens is typically equal to the valency of the cation; additional hydrogens pair to form molecules with electronic states far below the Fermi energy causing low-symmetry structures with large unit cells. At high pressures, molecules become unstable, and all hydrogens become atomic. This study uses density functional theory, adopting BaH₄ as a reference compound, which is compared with other stoichiometries and other cations. Increased temperature and zero-point motion also favor high-symmetry atomic states, and picosecond-timescale breaking and remaking of the bond permutations via intermediate H₃^- units.

SUBMITTER: Marques M

PROVIDER: S-EPMC10424234 | biostudies-literature | 2023 Aug

REPOSITORIES: biostudies-literature

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H2 Chemical Bond in a High-Pressure Crystalline Environment.

Marqués Miriam M Peña-Alvarez Miriam M Martínez-Canales Miguel M Ackland Graeme J GJ

The journal of physical chemistry. C, Nanomaterials and interfaces 20230731 31

We show that the hydrogen in metal superhydride compounds can adopt two distinct states-atomic and molecular. At low pressures, the maximum number of atomic hydrogens is typically equal to the valency of the cation; additional hydrogens pair to form molecules with electronic states far below the Fermi energy causing low-symmetry structures with large unit cells. At high pressures, molecules become unstable, and all hydrogens become atomic. This study uses density functional theory, adopting BaH< ...[more]

PMID: 37583438

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