Babbush, RyanParkhill, JohnAspuru-Guzik, Alan2014-05-062013Babbush, Ryan, John Parkhill, and Alán Aspuru-Guzik. 2013. “Force-field functor theory: classical force-fields which reproduce equilibrium quantum distributions.” Frontiers in Chemistry 1 (1): 26. doi:10.3389/fchem.2013.00026. http://dx.doi.org/10.3389/fchem.2013.00026.2296-2646http://nrs.harvard.edu/urn-3:HUL.InstRepos:12152888Feynman and Hibbs were the first to variationally determine an effective potential whose associated classical canonical ensemble approximates the exact quantum partition function. We examine the existence of a map between the local potential and an effective classical potential which matches the exact quantum equilibrium density and partition function. The usefulness of such a mapping rests in its ability to readily improve Born-Oppenheimer potentials for use with classical sampling. We show that such a map is unique and must exist. To explore the feasibility of using this result to improve classical molecular mechanics, we numerically produce a map from a library of randomly generated one-dimensional potential/effective potential pairs then evaluate its performance on independent test problems. We also apply the map to simulate liquid para-hydrogen, finding that the resulting radial pair distribution functions agree well with path integral Monte Carlo simulations. The surprising accessibility and transferability of the technique suggest a quantitative route to adapting Born-Oppenheimer potentials, with a motivation similar in spirit to the powerful ideas and approximations of density functional theory.en-USeffective potentialspath integral molecular dynamicsnuclear quantum propagationliquid hydrogendensity functional theoryJournal Article2014-05-0610.3389/fchem.2013.00026