High-pressure formation and stabilization of iridium hydrides

TL;DR

This study predicts the formation and stability of various iridium hydrides under high pressure using ab-initio calculations, identifying specific pressures where these compounds become thermodynamically and dynamically stable.

Contribution

It provides the first ab-initio predictions of high-pressure iridium hydrides, detailing their stability thresholds and bonding characteristics.

Findings

IrH_x hydrides stabilize at specific high pressures

Dihydride stabilizes dynamically around 14 GPa

Trihydride remains more stable than dihydride up to 75 GPa

Abstract

A class of iridium hydrides, IrH_x (x=0.5, 1-4, 6), is calculated at ab-initio level using the DFT. A number of hydrides are predicted to stabilize in the excess hydrogen environment and upon compression. The threshold pressure for thermodynamical stabilization is calculated to ~5 and ~14 GPa at which, respectively, a trihydride (P6_3mc) and a dihydride (Ibam) stabilize with respect to decomposition into pure element. The dihydride (Ibam) is calculated to stabilize dynamically at P~14 GPa and the trihydride at P > 25 GPa. In both the di- and trihydride iridium atoms form short directional contacts with hydrogens, typical for covalent bonds. The trihydride exhibit molecular character and its relative stability is calculated to be higher than that of the dihydride, at least up to approx. 75 GPa.