Prediction of Thermophysical Properties of Explosives by Molecular Simulations

Over the past few years, there has been significant research in the development of new Insensitive Munitions (IM) compounds due to their thermal stability and low shock sensitivity. It is necessary to determine the environmental impact of these compounds before they are put to widespread use in terms of bioaccumulation potential and aqueous solubility. In this work, we have developed forcefields for six explosive compounds, 2,4-dinitroanisole (DNAN), N-methyl-p-nitroaniline (MNA), Dinitropyrazole (DNP), Nitrotriazolone (NTO), 1-methyl-2,4,5-trinitroimidazole (MTNI) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) to predict their octanol-water partition coefficients, Henry's law constants and also vapor-liquid equilibria, vapor pressure and critical points. For the non-bonded interactions, Lennard-Jones parameters are obtained from the TraPPE-UA [1,2,3] and TraPPE-EH force fields [4] from similar functional groups. The partial charges are fitted to reproduce partition coefficients and Henry's law constants from the experiment. NPT molecular dynamics simulations coupled with the free energy perturbation technique is used to compute the physicochemical properties and Gibbs-Duhem integration is used to determine the vapor-liquid equilibria, vapor pressure and critical parameters.

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[2] M.G.Martin, J.I.Siepmann, J.Phys.Chem.B, 104 (8008).

[3] J.M.Stubbs, J.J.Potoff, J.I.Siepmann, J.Phys.Chem.B, 108 (17596).

[4] N.Rai, J.I.Siepmann, J.Phys.Chem.B, 111 (2007).