Molecular dynamics predictions of viscosity for organophosphorus liquids

When studying physical properties of highly toxic chemicals, such as chemical warfare agents (CWAs), molecular dynamics (MD) simulations can serve as an alternative to experimental measurements. We performed MD simulations to calculate viscosity of four organophosphorus liquids, CWAs, sarin, and soman, as well as their simulants, DMMP and DIMP, in the temperature range from 0 to 60 degrees C. The molecules were represented with Transferable Potentials for Phase Equilibria United Atom (TraPPE-UA) force field; the calculations were performed using the Green-Kubo method. The results for sarin and DMMP are in good agreement with previously published experimental data, which justifies the use of the TraPPE-UA force field for other organophosphorus compounds. Therefore we predicted viscosity of DIMP and soman, for which the experimental data were unavailable. Our results suggest that for applications where liquid viscosity is important, DMMP is a suitable simulant for sarin, and DIMP is a suitable simulant for soman.