The different methods were tested to determine the similarity of the resulting geometries, which can be seen in Figure . The geometry differences were quantified using root mean square deviations (RMSD), calculated using ArbAlign. We tested all four iodine compounds, the oxy-acids will be covered here, while the oxides are covered in Section S2.1 of the SI. For IsA and IA we used the structures optimized at DKH-CCSD(T)/TZVPP as the reference structure.