Route to high-Tc superconductivity of BC7 via strong bonding of boron-carbon compound at high pressure

We have analyzed the compositions of boron-carbon system, in which the BC7 compound is identified as structural stability at high pressure. The first-principles calculation is used to identify the phase diagram, electronic structure, and superconductivity of BC7. Our results have demonstrated that the BC7 is thermodynamically stable in the diamond-like P4m2 structure at a pressure above 244 GPa, and under temperature also. Feature of chemical bonds between B and C atoms is presented using the electron localization function. The strong chemical bonds in diamond-like P4m2 structure are covalent bonds, and it exhibits the s-p hybridization under the pressure compression. The Fermi surface shape displays the large sheet, indicating that the diamond-like P4m2 phase can achieve a high superconducting transition temperature (T-c). The outstanding property of BC7 at 250 GPa has manifested very hig h-T-c of superconductivity as 164 K, indicating that the carbon-rich system can induce the high-T-c value as well.