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 sp3 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∗μ∗ of 0.13).

► We predicted five possible structures of B2CN using ab initio calculations.
► The current Pmm2 and Pmma B2CN are more stable than the earlier structures.
► The predicted B2CN structures are superhard and superconducting.
► The difference in superconductivity is related to the relatively lower frequency.