Crystal and electronic structures of superhard B2CN : An ab initio study

With the increasing demand for specific applications in high pressure and electronic devices, the search for superhard superconducting materials remains a topic of great interest. Using particle swarm optimization algorithm, we report five competitive structures with clear tetrahedrally sp 3 hybridization, among which two metallic orthorhombic structures (Pmm2 and Pmma) with the maximal stable bonds (C–C + B–N) are energetically more favorable than earlier proposed structures. Further first principles calculations suggest that the predicted five structures possess simultaneously superhard and superconducting properties. The five structures are with the similar calculated hardness (56–58 GPa), but show distinct difference in superconducting critical temperature, ranging from 2 to 53 K (with the Coulomb parameter μ ∗ of 0.13).