Reaction constants and energy barriers from the metadynamics simulations using WMetaD associated with different La-Cl association reactions are presented in Table . PMF data from Guan et al. is used to recalculate log K ∞ eq for the AIMD reference in Table using the method described in the SI. Making these corrections leads to a maximum difference of about one log unit in log K ∞ eq of the studied reactions. To make a credible comparison, PIM association constants obtained from the small simulation boxes are compared with the AIMD data. The effects of box size are discussed subsequently. La-Cl complexes show step-wise association reactions as