A Density Functional Theory Study of Adsorption and Decomposition of Nitroamine Molecules on the Al(111) Surface

The density functional theory generalized gradient approximation has been used to study the adsorption of nitroamine molecules on the Al(111) surface. The calculations employ a 4 × 4 aluminum slab with three layers and three-dimensional periodic boundary conditions. There exist both physical and chemical adsorptions associated with different NH 2 NO 2 molecule orientations and particular aluminum surface sites. For the nondissociative adsorption, the nitro oxygen atom orients to the Al surface. In the case of dissociative chemisorption, the O and N atoms bind with the Al surface. The O and N atoms of broken down N−O and N−N bonds form strong Al−O and Al−N bonds with the neighboring Al sites around the dissociation sites. Moreover, the radical species obtained as a result of N−O and N−N bond dissociation remains bonded to the surface. The largest adsorption energy is −893.8 kJ/mol. For the dissociation adsorption configurations, a significant charge transfer occurs. The most charge transfer is 3.04 e from the Al surface to the NH 2 NO 2 molecule. The change of the electronic structures is obvious due to the dissociation of the N−O and N−N bonds and the formation of strong Al−O and Al−N bonds. It can be inferred that the aluminum surface is readily oxidized by the adsorbate of nitroamine, by dissociation of either the O and N atoms from the nitro group or the N atom from the amino group.