High temperature superconducting phase of HBr under pressure predicted by first-principles calculations

TL;DR

This study predicts a high-temperature superconducting phase of HBr under high pressure using first-principles calculations, identifying conditions for stability and ways to enhance Tc.

Contribution

It introduces the P4/nmm phase of HBr as thermodynamically stable at high pressure and explores how atomic substitution can further increase superconducting temperature.

Findings

P4/nmm HBr stable between 150-200 GPa

Superconducting Tc around 73 K at 170 GPa

Chlorine substitution raises Tc to 95 K

Abstract

The high pressure phases of HBr are explored with an ab initio crystal structure search. By taking into account the contribution of zero-point energy (ZPE), we find that the P4/nmm phase of HBr is thermodynamically stable in the pressure range from 150 to 200 GPa. The superconducting critical temperature (Tc) of P4/nmm HBr is evaluated to be around 73 K at 170 GPa, which is the highest record so far among binary halogen hydrides. Its Tc can be further raised to around 95K under 170 GPa if half of the bromine atoms in the P4/nmm HBr are substituted by the lighter chlorine atoms. Our study shows that, in addition to lower mass, higher coordination number, shorter bonds, and more highly symmetric environment for the hydrogen atoms are important factors to enhance the superconductivity in hydrides.