Violation of the Minimum H-H Separation "Rule" for Metal Hydrides

Abstract

Using gradient-corrected, all-electron, full-potential, density-functional calculations, including structural relaxations, it is found that the metal hydrides $RT$InH${}_{1.333}$ (R = La, Ce, Pr, or Nd; T = Ni, Pd, or Pt) possess unusually short H-H separations. The most extreme value (1.454 Å) ever obtained for metal hydrides occurs for LaPtInH${}_{1.333}$. This finding violates the empirical rule for metal hydrides, which states that the minimum H-H separation is 2 Å. Electronic structure, charge density, charge transfer, and electron localization function analyses on $RT$InH${}_{1.333}$ show dominant metallic bonding with a non-negligible ionic component between T and H, the H-H interaction beingweakly metallic. The paired, localized, and bosonic nature of the electron distribution at the H siteare polarized towards La and In which reduces the repulsive interaction between negatively charged H atoms. This could explain the unusually short H-H separation in these materials. Also, R-R interactions contribute to shielding of the repulsive interactions between the H atoms.

5 pages, 3 figures

References in corpus (1)

• Electronic structure, phase stability and chemical bonding in Th${}_2$Al and Th${}_2$AlH${}_4$

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