A New Superhard Phase of C3N2 Polymorphs

Abstract

Carbon nitrides are excellent candidates for extreme hardness materials. In this work, a new I4.3m phase of C3N2 has been uncovered by replacing part of the nitrogen atoms in the cagelike diamondoid nitrogen N10 with carbon atoms. This phase is mechanically and dynamically stable up to at least 50 GPa. The elastic anisotropy of I4.3m-C3N2 is investigated by comparing with previously proposed -¿-C3N2. The tensile directional dependence of Young-fs modulus obeys the following trend: E[111] < E[110] > E[100]. Electronic structure calculations reveal that I4.3m-C3N2 is hole conducting. Hardness calculation shows that the I4.3m-C3N2 is superhard with a hardness of 72.9 GPa.