Potential existence of Xe3CO2 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-Xe₃CO₂, 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 Xe₆C₂O₄ 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 (-4.650.28em0exe/⁵). This leads to an unusual sp³-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 Xe₃CO₂ in various astronomical objects.