Figure 1.

Individual algorithm steps of the molecular particle model. 1) First-order reactions are determined by a probabilistic success rate depending on the microscopic reaction rate per molecule k_micro,i and the time step Δt. 2) The Brownian motion for every molecule is determined by its individual diffusion coefficient D_i. 3) For second-order reactions, success is determined upon collision given the microscopic reaction, the sum of the diffusion coefficient D_ij = D_i + D_j, the sum of the radii of the colliding particles r_ij = r_i + r_j, and the time step (24). 4) Boundary reactions are given as constant particle boundaries, wherein the removal or insertion of particles is done if the number of particles deviates from the given boundary condition.