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((4) over bar)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((4) over bar)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).