Kinetic Monte Carlo Simulations of Nitrogen-Carbon Gas-Surface Reaction at High Temperatures

An atomic-scale computational simulation framework for investigating the reaction between gaseous nitrogen with a solid carbon surface is developed. First, a sterically resolved, atomic-scale kinetic mechanism with reaction rates derived from first principles is constructed, using existing Density Functional Theory (DFT) data from literature. This mechanism is then implemented using the Kinetic Monte Carlo (KMC) method. Simulations of the reaction of atomic and molecular nitrogen with a single graphene sheet with pre-existing monovacancy defects show that carbon is exclusively removed as CN from edge carbon atoms, leading to pitting of the carbon surface. The simulations are validated by comparison to carbon nitridation experiments on the atomic (molecular beam) and macroscopic scale (flow tube reactor) available in literature. The presented framework is capable of simulating the nitrogen-carbon reaction at relevant time-and lengthscales for ablation, and will be useful for modelling the surface evolution of carbon materials during ablation in nitrogen-containing gases.