These symbols also indicate relational information. For example, LMκ16 and TSκ 2 have common elements (site atom-16) and one connection difference (site atom-17). We refer to such a single connectivity-configuration difference as "first order" with the R de c process connecting these two species described as a "first-order motion". Similarly, if the differences in atomconnectivity configuration involves two connections (one bonder's configuration changing by 2 connections, or two bonders changing by 1 connection each), this is referred to as "second order". These terms find application when referring to pathways on the corresponding PESs. Formal definition for these motions-order relationships in the Supplementary Information.