Potential existence of ${\mathrm{Xe}}_3{\mathrm{CO}}_2$ compounds with distinct Xe-C covalent bonds under pressures of Earth's core

Noble gas compounds have attracted significant research attention, mainly due to their intriguing chemical behavior under high-pressure conditions. In this paper, we identify a compound, $C2/m\text{−}{\mathrm{Xe}}_3{\mathrm{CO}}_2$, through a synergistic approach combining a particle-swarm optimization empowered structure search and first-principles calculations within a wide pressure range of 200–400 GPa, covering the pressure range of Earth's core. This compound features layered ${\mathrm{Xe}}_6{C}_2{O}_4$ sublattices, showing distinct covalent Xe-C bonds, supported by the calculated electron localization function. The presence of the covalent bonds is further corroborated by the large value of the integrated crystal orbital Hamilton population ($-4.02$ eV/pair) and the large negative Laplacian ($-4.65e/{\text{Å}}^5$). This leads to an unusual $s{p}^3$-like hybridization in carbon, involving two oxygen atoms, one carbon atom, and one xenon atom. Additionally, two-phase method molecular dynamics simulations suggest that the compound exhibits liquid-state behavior at 200 GPa and 5000 K above the geotherm of the Earth's core. This shows a potential role for the compound in the liquid phase as a reservoir for the "missing Xe" phenomenon. Our findings not only enhance the understanding of bonding behavior in noble gas compounds, but also suggest the potential presence of ${\mathrm{Xe}}_3{\mathrm{CO}}_2$ in various astronomical objects.