To account for bidentate adsorbates binding through two sites, we introduce the concept of "adsorption edges", i.e. the edges of the graph which connect the identified active sites. An example of the adsorption edges for C 3 H 5 adsorption is illustrated in the avi video accompanying Figure for a (111) surface of Au 3 Pd L1 2 . Of the edges present in the full graph, the ones which result in unique pairs of the symmetrically unique active sites are symmetrically unique themselves. For N unique active sites, and adsorption graph will contain between N and N ! unique adsorption edges.