BROWNIAN DYNAMICS SIMULATIONS OF DIFFUSION-CONTROLLED REACTIONS WITH FINITE REACTIVITY

A new Brownian dynamics simulation technique is presented for the calc ulation of the effective rate constant for diffusion controlled reacti ons with a finite intrinsic reactivity. The technique is based on the calculation of the recollision probability of a molecule with a reacti ve site using a large number of Brownian trajectories, when the probab ility of reaction upon collision with the reactive site (phi(f)) is le ss than unity. The technique is a modification of the earlier work of Northrup et al. [J. Chem. Phys. 80, 1517 (1984)], and is applied to th e case of a uniformly reactive target sphere and a target sphere with axially symmetric reactive patches. A theoretical analysis is presente d to relate phi(f) to the intrinsic surface reaction rate constant (k' ). Computational results for the uniformly reactive sphere are in exce llent agreement with theory, and those for the sphere with patches are in very good agreement with the results obtained using a different co mputational technique [Allison ct al., J. Phys. Chem. 94, 7133 (1990)] . The proposed method requires the computation of the recollision prob ability to a high accuracy; however, this does not result in computati onal times greater than those of Allison er al. [J. Phys. Chem. 94, 71 33 (1990)]. The new method has the advantage that the results of the B rownian dynamics simulation are independent of k' and can subsequently be used to calculate the effective rate constant for any given value of k'. (C) 1997 American Institute of Physics.