THEORETICAL-STUDY OF A MODEL ISOMERIZATION REACTION AT THE LIQUID-SOLID INTERFACE

The thermodynamics and dynamics of an isomerizing diatomic (modeled using a double-well potential) at the interface between a flat wall and a Lennard-Jones liquid are studied using molecular dynamics and are compared with those of the same reaction in the bulk liquid. The potential of mean force along the reaction coordinate is calculated in the bulk and at the surface and used to estimate the transition state theory rate constant. For the particular system studied here (weakly adsorbed isomerizing molecule), the liquid contribution to the activation free energy is much smaller at the interface, but the total activation energy is the same as in the bulk because of a contribution from the binding to the surface. Calculations of the transmission coefficients using molecular dynamics reactive flux correlation show that the surface and bulk liquid contributions are nearly equal even though the effective density of the liquid near the surface is a factor of three larger than the bulk density. Insight into these results is obtained by calculations of the dynamical friction as a function of orientation and bulk density. © 1995 American Institute of Physics.