Electronegativity identification of novel superhard materials

We show that electronegativity can be used to effectively identify the hardness of crystal materials on the basis of a new microscopic model for hardness. Bond electronegativity is proposed to characterize the electron-holding energy of a bond, which is the intrinsic origin of hardness. Applying this model to c-BC2N materials, we confirm the proper bond composition of the experimentally observed phase of c-BC2N, in which the bond ratio N(C-C)N(B-N)N(B-C)N(C-N) is 3:3:1:1. A number of bonds that can or cannot form a superhard material are qualitatively distinguished, which enables us to explore novel superhard materials by screening possible elemental combinations.