New Phases and Dissociation-Recombination of Hydrogen Deuteride to 3.4 Megabar

TL;DR

This study investigates the high-pressure behavior of solid hydrogen deuteride up to 3.4 megabar, revealing phase transitions, dissociation-recombination processes, and non-metallic new phases through infrared absorption spectroscopy.

Contribution

It reports the discovery of three new high-pressure phases of hydrogen deuteride and details the dissociation-recombination process at extreme pressures, expanding understanding of molecular behavior under such conditions.

Findings

Dissociation and recombination occur above 198 GPa.

Three new high-pressure phases are identified.

Molecular concentrations reach steady state in ~20 hours at 200 GPa.

Abstract

We present infrared absorption studies of solid hydrogen deuteride to pressures as high as 3.4 megabar in a diamond anvil cell and temperatures in the range 5 to 295 K. Above 198 GPa the sample transforms to a mixture of HD ,H2 and D2, interpreted as a process of dissociation and recombination. Three new phases-lines are observed, two of which differ remarkably from those of the high-pressure homonuclear species, but none are metallic. The time-dependent spectral changes are analyzed to determine the molecular concentrations as a function of time; the nucleon exchange achieves steady state concentrations in ~20 hours at ~200 GPa.