MOLECULAR-DYNAMICS STUDY OF A SOLUTE-TRANSFER REACTION ACROSS A LIQUID-LIQUID INTERFACE

The aim of this study is to model a solute transfer through a liquid-liquid interface (LLI) by an activated process. This transfer has been investigated by molecular dynamics simulation (MD). Modified Lennard-Jones potential functions have been used to model the solute and the two solvents which compose the LLI. The transfer reaction investigated is the change of solvation of the solute particle when it crosses the LLI. The full rate constant is calculated as the product of the transition-state theory (TST) rate constant and the transmission coefficient (dynamical contribution). The free energy barrier, encountered by the solute crossing the interface, is derived from the mean force acting on the solute. The TST rate constant of the transfer is deduced from the height and the shape of this barrier. The transmission coefficient is obtained from the plateau value of the normalized reactive flux. The prediction of the Kramers theory is compared with the MD results and discussed with respect to the specificity of our model.