Ab initio treatment of the behavior of TNT in soil

Computational algorithms have been very useful to study molecular interactions between explosives and different types of soils. In this work ab initio molecular orbital calculations were employed to study the interaction of 2,4,6-trinitrotoluene (TNT) with the basal siloxane surface of clay minerals. The intermolecular interaction energy, the vibration frequencies and efficient computational algorithms have been tested for the complex of TNT with the siloxane surface site of clay minerals. Two cluster models have been developed to represent the TNT on the siloxane surface of clay minerals. They have been employed in order to determine the changes in the spectroscopic signature of TNT. The results obtained provide information about the interaction energy of TNT on clays. The binding energy between the TNT and the basal siloxane surface was -38 kJ/mol, obtained with MP2//HF/6-31+G(d) level of theory and basis set, respectively. The calculated interaction has their minimal at separation between the two molecules of 3.5 Å. The theoretical IR spectra of the interaction was obtained with DFT//HF methods and the 6-31+G(d) basis set. The calculation predicted a shifting effect in NO2 bands, due to the interaction. The results are in excellent agreement with available experimental data. Further, result of such theoretical studies could contribute to an understanding of the interaction energy of the other kinds of explosives that may be occurring in other environments.