The effect of SOC stabilization was also tested for dimers of iodine oxy-acids, which can be seen in Figure . We chose to showcase the HOIO dimer due to the significant size of the stabilization energy, the corresponding results on the HOIO 2 dimer is shown in Figure in Section S3.3 of the SI. In Figure , it can be seen that the SOC stabilization reduces during dimer formation, where the total stabilization before dimer formation is -2.8 kcal/mol for 10 roots and approx. -1.8 kcal/mol after dimer formation. The dimer formation increases the valency of iodine, which has previously been shown to decrease the effect of SOC stabilization. In contrast to the results in Figure it can be observed that the stabilization energy difference, seen in Figure , is less sensitive to the number of roots included in the TD-DFT calculation. This is likely because the convergence of SOC stabilization energy for monomers and dimers are similar and cancel out. Given our previous choice of including 10 states in the calculation, we can see that the difference between the combined monomer SOC stabilization and the dimer SOC is 0.65 kcal/mol. This difference means that if SOC was not included in the calculation then we would overestimate the stability of the dimers by up to 0.65 kcal/mol. Adding more molecules to the cluster, which need not contain iodine, would lead to increased valency of iodine which reduces the SOC of iodine in the clusters. This increases the difference between the SOC of the clustered iodine and the SOC of the constituent monomers, which contributes to increasing error in the binding free energy if this SOC contribution is neglected.