(635c) A Hybrid MC-DFT Method for Studying Multi-Dimensional Entropic Forces

Entropic force has been the focus of many recent theoretical studies because of its fundamental importance in solution thermodynamics and its close relevance to a broad range of practical applications. Whereas previous investigations are mostly concerned with the potential energy as a one-dimensional function of the separation, here we propose a hybrid method for studying multi-dimensional systems by combining Monte Carlo simulation for the microscopic configurations and the density functional theory for the free energy. We demonstrate that the hybrid method predicts the potential of mean force between a test particle and various concave objects in a hard-sphere solvent in excellent agreement with the results from alternative but more expansive computational methods. In particular, the hybrid method captures the entropic force between asymmetric particles and its dependence on the particle size and shape that underlies ?lock and key? interactions. Because a single molecular model is used for both the theory and the simulation, we expect that the hybrid method provides a new avenue to predicting entropic forces in complex molecular systems.