Dehydrogenation through the pressure-induced polymerization processes of phosphine

TL;DR

This study investigates the high-pressure behavior of phosphine (PH3), revealing its dehydrogenation into phosphorus hydrides P2H4 and P4H6, which are linked to superconductivity at high pressures through experimental and theoretical analysis.

Contribution

It provides new insights into the pressure-induced transformation and stability of phosphorus hydrides, elucidating their role in high-pressure superconductivity.

Findings

PH3 is stable up to 8 GPa and dehydrogenates at higher pressures.

P2H4 and P4H6 are experimentally verified as stable intermediates.

Superconducting transition temperatures of P4H6 are predicted at 13 K and 67 K at high pressures.

Abstract

PH3 is studied to understand the superconducting transition and responsible stoichiometry under high pressure by means of Raman, IR, and x-ray diffraction (XRD) measurements, and theoretical calculations. It is found PH3 is stable up to about 8 GPa and then starts to dehydrogenate through two dimerization processes at room temperature as pressure up to 25 GPa. Two resulting phosphorus hydrides, P2H4 and P4H6, are verified experimentally and can be recovered to ambient pressure. On further compression above 35 GPa, P4H6 directly decomposes into elemental phosphorus. The superconductivity transition temperatures of P4H6 at 100 and 200 GPa have been predicted to be 13 and 67 K in agreement with reported results, suggesting it might responsible for the superconductivity at higher pressures. Our results clearly show that P2H4 and P4H6 are only stable P-H compounds between PH3 and elemental phosphorus, shedding light on the superconducting mechanism.