Stability of XeK4 compound under extreme conditions

Noble gas elements exhibit chemical reactivity under high pressure, forming novel compounds through reactions with other substances, which has become a recent focus in condensed matter physics research. By combining first-principles calculations with crystal structure prediction methods, we propose six unconventional Xe-K compounds under high pressure, namely Xe₄K, Xe₃K, Xe₃K₂, Xe₂K, XeK, and XeK₄. In addition to previously proposed Xe-rich compounds, we introduce an unconventional K-rich compound, XeK₄, which remains stable over a considerable pressure range from 49 to 104 GPa and a high-pressure phase of Xe₃K. Both XeK₄ and Xe₃K demonstrate metallic properties with a strong ionic Xe-K bond within their stable pressure range. Further ab initio molecular dynamics simulations indicate that XeK₄ undergoes a solid-to-liquid transition with increasing temperature, while the other Xe-K compounds maintain solid-state characteristics. The solid or liquid stability pressure ranges of Xe-K compounds cover the pressure and temperature conditions of the Earth's mantle, suggesting that XeK₄ and other Xe-K compounds might act as possible constitutes and exist in the Earth's mantle. These results could provide essential information for understanding the Xe-K compounds and the Xe chemistry at high pressure.