Stable xenon nitride at high pressures

Abstract

Nitrides in many ways are fascinating since they often appear as superconductors, high-energy density, and hard materials. Though there exist a large variety of nitrides, noble gas nitrides are missing in nature. Pursuit of noble gas nitrides has therefore become the subject of topical interests, but remains as a great challenge since molecular nitrogen (${\mathrm{N}}_{2}$, a major form of nitrogen) and noble gases are both inert systems and do not interact at normal conditions. We show through a first-principles swarm-structure search that high pressure enables a direct interaction of ${\mathrm{N}}_{2}$ and xenon (Xe) above 146 GPa. The resultant Xe nitride has a peculiar stoichiometry of ${\mathrm{XeN}}_{6}$, possessing a high-energy density of approximately $2.4\phantom{\rule{0.28em}{0ex}}{\mathrm{kJ}\phantom{\rule{0.16em}{0ex}}\mathrm{g}}^{\ensuremath{-}1}$, rivaling that of the modern explosives. Structurally, ${\mathrm{XeN}}_{6}$ is intriguing with the appearance of chaired ${\mathrm{N}}_{6}$ hexagons and unusually high 12-coordination of Xe bonded with N. Our work opens up the possibility of achieving Xe nitride with superior high-energy density whose formation is long sought as impossible.