Understanding the Transferability of the Optimized Potentials for Liquid Simulations (OPLS-AA)

Department of Chemical Engineering and Materials Science, Wayne State University

The accuracy and transferability of the Optimized Potentials for Liquid Simulations All Atom (OPLS-AA) force field is evaluated for linear and branched isomers of alkanes up from methane to octane. Of particular interest are highly branched compounds, such as 2,2,3,3-tetramethylbutane, 2,2,3-trimethylpentane and 2,2,4-trimethylpentane. Vapor-liquid coexistence curves, vapor pressures, heats of vaporization and critical points are determined from Gibbs ensemble Monte Carlo simulations. The predictions follow experimental trends, but significant quantitative differences are observed between simulation and experiment. These results are used to provide insight into the transferability of empirical force field parameters to a broad range of molecular topologies and local bonding environments.