has characteristic has parameter Smoluchowski equation based method Brownian diffusion Smoluchowski method 1 1 1 1 http://identifiers.org/pubmed/16204833 In the Brownian diffusion Smoluchowski method, ''each molecule is treated as a point-like particle that diffuses freely in three-dimensional space. When a pair of reactive molecules collide, such as an enzyme and its substrate, a reaction occurs and the simulated reactants are replaced by products. [..] Analytic solutions are presented for some simulation parameters while others are calculated using look-up tables''. Supported chemical processes include molecular diffusion, treatment of surfaces, zeroth-order-, unimolecular-, and bimolecular reactions. Smoldyn Greens function reaction dynamics spatial description discrete variable progression with fixed time step Brownian diffusion accuracy surface-bound epsilon neighbour distance virtual box size