Stability of ${\mathrm{XeK}}_4$ 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 ${\mathrm{Xe}}_{4}K$, ${\mathrm{Xe}}_{3}K$, ${\mathrm{Xe}}_3{K}_2$, ${\mathrm{Xe}}_{2}K$, XeK, and ${\mathrm{XeK}}_4$. In addition to previously proposed Xe-rich compounds, we introduce an unconventional K-rich compound, ${\mathrm{XeK}}_4$, which remains stable over a considerable pressure range from 49 to 104 GPa and a high-pressure phase of ${\mathrm{Xe}}_{3}K$. Both ${\mathrm{XeK}}_4$ and ${\mathrm{Xe}}_{3}K$ demonstrate metallic properties with a strong ionic Xe-K bond within their stable pressure range. Further ab initio molecular dynamics simulations indicate that ${\mathrm{XeK}}_4$ 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 ${\mathrm{XeK}}_4$ 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.