Crystal Structures and Electronic Properties of Xe-Cl Compounds at High Pressure

Crystal structure prediction techniques coupled with enthalpies obtained at 0 K from density functional theory calculations suggest that pressure can be used to stabilize the chlorides of xenon. In particular, XeCl and XeCl₂ were calculated to become metastable by 10 GPa and thermodynamically stable with respect to the elemental phases by 60 GPa. Whereas at low pressures Cl₂ dimers were found in the stable phases, zigzag Cl chains were present in Cmcm XeCl at 60 GPa and atomistic chlorine comprised P6₃/mmc XeCl and Fd3̄m XeCl₂ at 100 GPa. A XeCl₄ phase that was metastable at 100 GPa contained monomers, dimers, and trimers of chlorine. XeCl, XeCl₂, and XeCl₄ were metallic at 100 GPa, and at this pressure they were predicted to be superconducting below 9.0, 4.3, and 0.3 K, respectively. Spectroscopic properties of the predicted phases are presented to aid in their eventual characterization, should they ever be synthesized.