Industrial property prediction using Towhee and LAMMPS

Abstract

Results are presented for Part 2 (density) and Part 3 (viscosity) of the First Industrial Fluid Properties Simulation Challenge (FIFPSC). In both cases, the physical properties were calculated using existing published force fields not specifically tuned to the problem at hand. No assessment of the accuracy of our predictions was made until the experimental values for each problem set were announced at the end of the competition. Liquid densities were computed for the Part 2 problem set using the Towhee Monte Carlo molecular simulation program and the Amber96, Charmm22, Compass, and OPLS-aa force fields. No single force field was able to provide parameters for all the molecules in the problem set, but the Amber96 force field had the best results of the four tested and a reasonable coverage of the problem set. Viscosities were computed for the Part 3 problem set using the LAMMPS molecular dynamics code. The Towhee program was used to generate equilibrium starting configurations. Only one force field, OPLS-aa, was used. The predicted viscosities showed average deviation of about 35% from the experimental values. In cases where the experimental density is known, substantially better accuracy can be expected.