Ground-state structure of semiconducting and superconducting phases in xenon carbides at high pressure

The 'missing Xe paradox' is one of the phenomena at the Earth's atmosphere. Studying the 'missing Xe paradox' will provide insights into a chemical reaction of Xe with C. We search the ground-state structure candidates of xenon carbides using the Universal Structure Predictor: Evolutionary Xtallography (USPEX) code, which has been successfully applied to a variety of systems. We predict that XeC₂ is the most stable among the convex hull. We find that the I[Formula: see text]2m structure of XeC₂ is the semiconducting phase. Accurate electronic structures of tetragonal XeC₂ have been calculated using a hybrid density functionals HSE06, which gives larger more accurate band gap than a GGA-PBE exchange-correlation functional. Specifically, we find that the I[Formula: see text]2m structure of XeC₂ is a dynamically stable structure at high pressure. We also predict that the P6/mmm structure of XeC₂ is the superconducting phase with a critical temperature of 38 K at 200 GPa. The ground-state structure of xenon carbides is of critical importance for understanding in the missing Xe. We discuss the inference of the stable structures of XeC₂. The accumulation of electrons between Xe and C led to the stability by investigating electron localization function (ELF).