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-BC(2)N materials, we confirm the proper bond composition of the experimentally observed phase of c-BC(2)N, 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.