Polynitrogen/Nanoaluminum Surface Interactions

First-principles density functional theory (DFT) calculations using the generalized gradient approximation (GGA) have been performed to study the adsorption of a series of all-nitrogen and high-nitrogen compounds of increasing sizes and complexity on the Al(111) surface. The calculations employ periodic slab models with 4 Al layers, ranging in size from (3times3) to (5times5) surface unit cells, and containing up to 144 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. The initial set of studies performed in the first year of this challenge project, which focused on the adsorption and reaction properties of N_x (x=1-5), NH_x (x=1-3), N₂H_x (x=1-4), N₃H, N₃H₃, and N₄H₄ species on Al(111), have been extended to include larger polynitrogen systems such as N₆, N₈, N₁₀, and N₁₂. The C₄₈N₁₂ fullerene-like molecule was included in this series in place of N₆₀, which was found to be unstable in the gas phase. Furthermore, simple nitrogen-containing heterocycles such as furazan (C₂N₂H₂O), 2H-1,2,3- and 4H-1,2,4-triazole (C₂N₃H₃), and 1H- and 2H-tetrazole (CN₄H₂) have been studied. Additional compounds of interest include the monosubstituted di(cyclopropyl )triazole (C₁₁N₆H₁₂) and di(cyclobutyl)triazole (C₁₃N₅H₁₆) derivatives of triazene. For these systems, surface interaction mechanisms involving both dissociative and nondissociative processes have been characterized as a function of molecular orientation and surface site. The - - dissociative mechanisms generally include elimination of one or more N₂ molecules.