Prediction of a series of superhard BC4N structures.

Six novel superhard BC 4 N- x (x = a , b , c , d , e , f) structures with low energies are determined by ab-initio evolutionary methodology using crystal structure analysis by particle swarm optimization (CALYPSO) code. These BC 4 N polymorphs employ a sp 3-hybrid network with BN and C layers connected alternatively, and with low energies close to those of the previously proposed lowest energy c -BC 4 N. The possible precursors and phase transition paths from hBC 4 N- x to novel BC 4 N- x (x = a , b , c , d , e , f) are also determined, and the energies of the hBC 4 N- x are close to each other under ambient pressure. Moreover, simulated XRD patterns of these novel BC 4 N structures show agreement with experimental data. The Raman main peak positions and intensities of these structures are also consistent. All indications point out the experimentally synthesized samples likely contain various BC 4 N structures. [Display omitted] • Six novel BC 4 N structures with superhard semiconductors are proposed via first principle calculation. • The simulated XRD patterns of novel BC 4 N structures show agreement with experimental data. • The possible precursors and phase transition paths from hBC 4 N- x to novel BC 4 N- x (x = a , b , c , d , e , f) are also determined. [ABSTRACT FROM AUTHOR]