First-Principles Calculations of the Adsorption of Nitromethane and 1,1- Diamino-2,2-dinitroethylene (FOX-7) Molecules on the Al(111) Surface

摘要

First-principles calculations based on spin-polarized density functional theory (DFT) and the generalized gradient approximation (GGA) have been used to study the adsorption of nitromethane (NM) and 1,1-diamino-2,2- dinitroethylene (FOX-7) molecules on the Al(111) surface. The calculations employ (3x3) aluminum slab geometries and 3D periodic boundary conditions. Based on these calculations, we have determined that both dissociative and nondissociative adsorption mechanisms are possible, depending on the molecular orientation and the particular surface sites involved. In the case of dissociative chemisorption, O abstraction by Al surface atoms is seen to be the dominant mechanism. The dissociated oxygen atom forms strong Al-O bonds with the neighboring Al sites around the dissociation sites. Additionally, the radical species obtained as a result of oxygen atom elimination remains bonded to the surface. In some instances, both oxygen atoms of the nitro group dissociate and oxidize the aluminum surface. Finally, for the case of nondissociative adsorption, various N-O-Al bridge-type bonding configurations can be formed. Based on the data provided from these studies, it can be concluded that oxidation of the aluminum surface readily occurs, either by partial or complete dissociation of the oxygen atoms from the NO2 group.