Evolution of hydrogen dissolution and superconductivity in Re-based solid solutions under pressure studied by ab initio calculations

Abstract

The dissolving of hydrogen (H) into rhenium (Re) is non-negligible in high-pressure experiments involving dense hydrogen and hydrogenous materials, in which rhenium is often used as a gasket material in the high-pressure diamond-anvil cell devices. However, the evolution of hydrogen dissolution into Re and the pressure-induced effects of hydrogen coupling on the superconductivity of metal-based hydrides remain poorly understood experimentally, and theoretical investigations are currently lacking. The present work addresses these issues by applying ab initio calculations for systematically investigating the dissolution of H atoms in Re systems, as well as the electronic properties, lattice dynamics, and electron-phonon coupling (EPC) in the corresponding interstitial Re hydrides. A series of ReHx compounds with increasing x in the range of 0 to 1 in increments of 0.125 are predicted to be stable at increasing pressures ranging from 1 to 50 GPa. It is found that H atoms generally play the role of impurities in the ReHx compounds except for ReH0.5 and ReH, where H atoms are integrated into the crystal structure. Moreover, the atomic configuration of the Re host lattice is basically preserved with increasing x and increasing pressure. Further analysis of the superconductive mechanism indicates that an increasing H concentration results in a decreased electronic density of states at the Fermi level and increasing phonon frequencies, which lead to a decrease of EPC λ and superconducting critical temperature. These findings quantitatively clarify the effects of hydrogen doping on superconductivity in metal-based hydrides, and thereby support the exploration of new types of superconductive hydrides.

Source-reported materials — not catalogue approval

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