Structure, Stability and Superconductivity of N-doped Lutetium Hydrides at kbar Pressures

Abstract

The structure of the material responsible for the room temperature and near ambient pressure superconductivity reported in an N-doped lutetium hydride [Nature, 615, 244 (2023)] has not been conclusively determined. Herein, density functional theory calculations are performed in an attempt to uncover what it might be. Guided by a range of strategies including crystal structure prediction and modifications of existing structure types, we present an array of Lu-N-H phases that are dynamically stable at experimentally relevant pressures. Although none of the structures found are thermodynamically stable, and none are expected to remain superconducting above ∼17 K at 10 kbar, a number of metallic compounds with fcc Lu lattices -as suggested by the experimental X-ray diffraction measurements of the majority phase -are identified. The system whose calculated equation of states matches best with that measured for the majority phase is fluorite-type LuH2, whose 10 kbar superconducting critical temperature was estimated to be 0.09 K using the Allen-Dynes modified McMillan equation.

A systematic study on the phase diagram and superconductivity of ternary clathrate Ca–Sc–H at high pressures

“…High-temperature superconductors have been a hot topic in condensed matter physics. Recently, with the experimental verification of room-temperature superconductivity in N-Lu-H compounds (T c E 294 K at P E 1 GPa), 1 the interest in the exploration of room-temperature superconducting materials has only grown in the past few years. The majority of research into hightemperature superconductor materials containing hydrogen has, until now, focused on binary hydrides.…”