RESUMO
N2O decomposition on iron-doped boron nitride nanotubes (Fe-BNNTs) was investigated by means of the density functional theory (M06-L). Two different forms of Fe-BNNTs, which are substitutions of the Fe atom into the boron-vacancy and nitrogen-vacancy sites of BNNTs, were used as the catalyst. Influence of the support plays a crucial role in the electronic configuration and catalytic reactivity of the iron atom. With the nitrogen surrounding (Fe(B)-BNNT), the iron behaves as a Lewis acid for accepting an electron from the lone-pair orbital of the N2O oxygen atom (η(1)-O complex). The catalytic process over this one at the transition state involves a synergistic σ-donation from the HOMO of N2O into a LUMO of the catalyst and the π-back-bonding from the metal d orbital into the π* orbital of N2O, leading to the cleavage of the N-O bond. The activation for this step is 22.5 kcal mol(-1). With the boron surrounding (Fe(N)-BNNT), the iron acting as a Lewis base plays a different role as compared with the iron in the case of Fe(B)-BNNTs. The HOMO of Fe(N)-BNNTs promotes the side-on binding mode of N2O on the iron center (η(2)-O,N complex), leading to the weakening of the N-O bond at the adsorption state. As a result, the decomposition over the Fe(N)-BNNTs takes place easily without an energy barrier.
RESUMO
The solvation structure around the dicyanoaurate(I) anion (Au(CN)2-) in a dilute nitromethane (CH3NO2) solution is presented from X-ray diffraction measurements and molecular dynamics simulation (NVT ensemble, 460 nitromethane molecules at room temperature). The simulations are based on a new solute-solvent force-field fitted to a training set of quantum-chemically derived interaction energies. Radial distribution functions from experiment and simulation are in good agreement. The solvation structure has been further elucidated from MD data. Several shells can be identified. We obtain a solvation number of 13-17 nitromethane molecules with a strong preference to be oriented with their methyl groups towards the solute.
RESUMO
A comprehensive analysis of metastable dissociation of 2,4-dinitrotoluene (DNT) parent anions formed by attachment of electrons of controlled energy is presented. We characterize the energy dependence and kinetic energy release of the reaction which competes with autodetachment. A surprising finding is a highly exothermic metastable reaction triggered by the attachment of thermal electrons which we relate to the well-known electrostatic ignition hazards of DNT and other explosives. Quantum chemical calculations are performed for dinitrobenzene in order to elucidate the process of NO abstraction.
