Abstract:

Nitrogen is a common impurity found in diamonds. We used three nonequivalent models to study carbon and nitrogen coadsorption on Ni(111) surface. Density functional theory (DFT) calculations were performed to study the influence of nitrogen upon the transformation of carbon's electronic structure during diamond synthesis. Three carbon adsorption models were constructed for comparison. Results indicated that nitrogen atoms destabilize the adsorption system and that the interaction between adatoms could not be ignored. According to the calculated interaction energies, the C-C interaction was stronger than the C-N interaction. Differences in the partial density of states (PDOSs) among the models suggested that the N-C interaction also improved catalysis to some extent, but this effect was not evident in comparison to the C-C interaction. The obtained atomic geometry and PDOS also indicated formation of CN compounds or graphite-like impurities if the adatom distance was too short, because they would occupy the same Ni(111)-(1×1) unit cell.

Key words: Coadsorption, Adsorption energy, Interaction energy, Partial density of states