Diffusive reaction rates from Brownian dynamics simulations: Replacing the outer cutoff surface by an analytical treatment

The algorithm of Northrup, Allison, and McCammon [J. Chem. Phys. 80, 1517 (1984)] for calculating diffusive reaction rates using Brownian dynamics simulations is reexamined. A new method is described in which a time-consuming portion of the algorithm is replaced by an analytical solution. When applied to two illustrative model systems, the new method is found to reduce the computational work by a factor of 2 or more.