Defective and amorphous structure of carbon nitride

There has been enormous interest in preparing the superhard material ${\mathrm{C}}_3{\mathrm{N}}_4$, with the large nitrogen concentration being one factor limiting preparation. Using an ab initio supercell approach we simulate the electronic structure about a N vacancy and investigate the effect it has on the bulk modulus of the material. We compare this with a relaxed cubic ${\mathrm{C}}_3{\mathrm{N}}_3$ structure with one N atom removed. The ability of the superlattice to model the electronic structure of the crystalline material is used to deduce properties of an amorphous structure within the ab initio framework. The amorphous form has a bulk modulus significantly lower than its crystalline counterpart and comparison of various structures suggests that the final strength of carbon nitride will ultimately depend upon the number of C-N bonds that can be formed during synthesis of the material.