Semiclassical Dynamics Simulation Research Articles

Activated rate processes: The reactive flux method for one-dimensional surface diffusion

We have implemented a semiclassical dynamics simulation method to investigate the effects of finite barrier heights and nonlinear potentials on the rate of diffusion of a particle which is coupled to a frictional bath and is traveling on a one-dimensional potential energy surface. The classical reactive flux method has been modified to account for semiclassical tunneling and above-barrier reflection. A novel perturbation theory treatment of the semiclassical dynamics is developed to simulate the motion of the particle when the coupling to the frictional bath is small and the particle’s motion is nearly conservative. Our simulation results support the theoretical prediction that the diffusion constant increases as friction decreases. We also find supporting evidence for an inverse isotope effect, as the diffusion constant for a classical particle can be larger than that of a corresponding quantum mechanical particle. The escape rate and the average energy of escaping particles are also found to be in good agreement with theoretical predictions.