Maximum N content in a-CNx by ab-initio simulations

Structures of amorphous CN_x materials are predicted by extensive ab-initio molecular-dynamics simulations (more than 800 trajectories) in a wide range of compositions and densities. The main attention is paid to the formation of N₂ molecules, with the aim to predict and explain the maximum N content in stable CN_x networks. The results show that the maximum N content is of ≈42 at.%. From the kinetics point of view, higher N contents lead to steeply increasing rate of N₂ formation during materials formation. From the thermodynamics point of view, higher N contents in a network may be temporarily stabilized by N₂ molecules sitting in voids around the network, but a subsequent N₂ diffusion into the atmosphere makes them unstable. The results are important for the design of CN_x (and other nitride) materials and pathways for their preparation for various technological applications.