An analysis of the bonding structure of nine different amorphous carbon-nitrogen alloys, $a\text{−}{\mathrm{C}}_{1-x}{\mathrm{N}}_x$, of concentrations $0⩽x⩽0.45$, is performed on ab initio generated atomic random networks. 216-atom periodically-continued cubic diamondlike supercells containing carbons and randomly substituted nitrogens were amorphized by “heating” them to a value below the melting temperature, using a Harris-functional based ab initio molecular dynamics code. After quenching, annealing, and optimizing, amorphous atomic structures were obtained where the nature of the bonding was studied using a cutoff determined by the first minimum of the corresponding partial radial distribution function. We find that, for low concentrations, tetravalent nitrogen is predominant, in agreement with experiment. For concentrations near 30% nitrogen molecules appear signaling the onset of the doping limit observed by experimentalists.

• Received 8 August 2005

DOI:https://doi.org/10.1103/PhysRevB.73.024206