Abstract
Molecular dynamics (MD) simulations were conducted to compare the performance of four force fields in
predicting thermophysical properties of tri-n-butyl-phosphate (TBP) in the liquid phase. The intramolecular
force parameters used were from the Assisted Model Building with Energy Refinement (AMBER) force field
model. The van der Waals parameters were based on either the AMBER or the Optimized Potential for
Liquid Simulation (OPLS) force fields. The atomic partial charges were either assigned by performing
quantum chemistry calculations or utilized previously published data, and were scaled to approximate the
average experimental value of the electric dipole moment. Canonical ensemble computations based on the
aforementioned parameters were performed near the atmospheric pressure and temperature to obtain the
electric dipole moment, mass density, and self-diffusion coefficient. In addition, the microscopic structure of
the liquid was characterized via pair correlation functions between selected atoms. It has been demonstrated
that the electric dipole moment can be approximated within 1% of the average experimental value by virtue of
scaled atomic partial charges. The liquid mass density can be predicted within 0.5-1% of its experimentally
determined value when using the corresponding charge scaling. However, in all cases the predicted self-
diffusion coefficient is signi ficantly smaller than a commonly quoted experimental measurement; this result
is qualified by the fact that the uncertainty of the experimental value was not available.