where 𝐴 is a prefactor that depends on the temperature and system (adsorbate, adsorbent). This is a simplified version of the transition probability used in TST-based methods. In the case of a unidimensional channel with a single possible transition, the diffusion coefficient is directly associated with the diffusion rate. The problem can be reduced to a unidimensional random walk with a given transition probability, and the diffusion coefficient is given by