Polynitrogen/Nanoaluminum Surface Interactions

First-principles density functional theory (DFT) calculations using the generalized gradient approximation (GGA) have been conducted to study the adsorption of a series of high-nitrogen compounds of increasing sizes and complexity on the Al(lll) surface. The calculations employ periodic slab models with 4 Al layers, ranging in size from (3times3) to (7times7) surface unit cells, and containing up to 196 Al atoms. Complementary quantum chemical calculations, utilizing DFT and second-order perturbation theory methods, of the ground state potential energy surfaces of the corresponding polynitrogen/high nitrogen species in the absence of the aluminum surface also have been performed. For the set of chemical species N_x(x=1,5), NH_x(x=1-3), N₂H_x(x=1-4) and N₃H, N₃H₃, and N₄H₄, the adsorption configurations at different surface sites and the corresponding binding energies have been determined. This analysis has been further extended to high-nitrogen compounds N₅H and N₆H₂. For these two systems it was found that the initial bonding to the surface takes place through a molecular mechanism (nondissociatively) with involvement of single or multiple N atoms of the molecule. However, dissociation on the surface can take place with small activation energies. This set of calculations has been further extended to include 1,3,5-triazene and 1,2,3-triazine (C₃H₃N₃) as well as larger substituted triazene systems such as C₉N₃₀ and C₁₅N₁₈. For these large systems it was found that bonding takes place through multiple N centers with formation of highly strained and deformed adsorption configurations. In a number of instances the adsorption takes place dissociatively with N₂ elimination.