Figure 4.

(a) Mean first-passage time for activation τ_on as a function of the volume V of the square-shaped reactor with periodic boundary conditions, obtained in on-lattice KMC simulations for three values of motility and (c₁ = 0.02, c₂ = 0.15), and other parameters with default values. For small V, τ_on grows exponentially with V (well-mixed regime), while for large V, τ_on decreases as 1/V. Every τ_on is a maximum-likelihood estimate from a time series with fixed censoring time, calculated based on thousands of trajectories and at least n_on = 10 observed switches. (b) Dependence of τ_on on the motility M for reactors of two different geometries, for the same parameters as in (a). For the square-shaped reactor, the expected τ_on grows exponentially with increasing motility M; for the long rectangular reactor with periodic boundary conditions, τ_on grows faster than but slower than .