ARTICLE pubs.acs.org/JPCA
Ionization-Enhanced Decomposition of 2,4,6-Trinitrotoluene (TNT) Molecules Bin Wang,*,† David Wright,‡ David Cliffel,‡ Richard Haglund,† and Sokrates T. Pantelides†,§,|| Department of Physics and Astronomy, ‡Department of Chemistry, and §Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235, United States Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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ABSTRACT: The unimolecular decomposition reaction of TNT can in principle be used to design ways to either detect or remove TNT from the environment. Here, we report the results of a density functional theory study of possible ways to lower the reaction barrier for this decomposition process by ionization, so that decomposition and/or detection can occur at room temperature. We find that ionizing TNT lowers the reaction barrier for the initial step of this decomposition. We further show that a similar effect can occur if a positive moiety is bound to the TNT molecule. The positive charge produces a pronounced electron redistribution and dipole formation in TNT with minimal charge transfer from TNT to the positive moiety.
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etection of explosives at low concentrations is an important problem in contemporary antiterrorism efforts, and significant progress has been made in the past few years in detection techniques for TNT and other explosives.1 16 Apart from antiterrorism efforts, the widespread and long-term use of TNT in both military and industrial applications leads to contamination of the environment in soil and groundwater.17 Moreover, TNT is poisonous and can cause skin irritation and harmful effects on the immune system. Thus, techniques both to detect and to remove TNT from the environment are needed, in principle at sensitivities approaching molecular levels. Thus, the understanding of molecular properties and catalytic reaction mechanisms of explosives could in principle be helpful in the design of viable detection systems with high sensitivity and selectivity,2,18 21 especially for mass spectrometry.14,22 25 Thermal decomposition of TNT has been widely studied experimentally26 and theoretically27,28 to understand the mechanism of the detonation process, especially for the initial reaction. The initial steps of the reaction could be different depending on the reaction conditions (temperature and pressure).26 On the basis of calculations,27,29 it has been proposed that transfer of one H atom of the CH3 moiety to the ortho-nitro group in TNT (illustrated in Figure 1a) is thermodynamically more favorable than other reactions, e.g., dissociation of the NO2 moiety, and dominates at lower temperature (e.g.,
