<i>Ab initio</i>simulations of amorphous carbon nitrides

Abstract

Density-functional ab initio molecular dynamics is used to study the incorporation of nitrogen into carbon networks. The resulting networks were analyzed using a Wannier-function technique for producing a localized orbital picture that provided us with a means of identifying bonding types of the nitrogen and carbon atoms within the disordered structures. Addition of nitrogen was found to cause a decrease in the fraction of ${\mathrm{sp}}^{3}$-bonded carbon and this effect is most severe at high density. These changes to carbon bonding are not confined to carbon atoms in the immediate vicinity of a nitrogen atom. The structure, and elastic and electronic properties of the networks are examined and compared with existing simulations and experimental observations. We found that removing electrons from the networks caused structural changes that could explain the two-state conductivity in amorphous carbon nitride memory devices.