Ab initio structural identification of high density cubic BC2N

We report ab initio total-energy calculations that examine the cubic-graphitic transformation and relative stability of two high density phases of cubic BC2N that have nearly identical crystal structure, lattice parameters, energetics and lattice dynamics, and equation of states over a large range of hydrostatic pressure. The calculated energy barriers for the formation and breaking of the bonds between the graphitic layers along different crystallographic directions clearly distinguish these two phases and provide important insights for the structural assignment of the experimentally synthesized high density cubic BC2N. We also identify a graphitic structure as a possible precursor for the synthesis of the high density cubic phase that has the highest critical tensile strength among the BC2N polymorphs.