To understand the origin of the best performance of D-CGCNN for IS2RE task, we investigated the effect of crystal graph representations on the prediction accuracy. A difference in graph representations of IS and RS was measured by graph edit distance, which is defined as the minimum number of operations, e.g., deletion, substitution and insertion, for two graphs to be identical . The graph edit distances were then normalized to obtain a graph similarity, where similarity value of 1 corresponds to the identical graph representations of IS and RS. Figure summarizes graph similarity values of all structures in 2e-ORR dataset and the average graph similarities of four different methods.