The overall picture of the data afforded by Figure is that the DFAs fail almost universally to predict a sufficiently small ω5 and to properly describe the flatness of the H-C-N bending potential. isolated clustering of data closer to the benchmark that is not witnessed in the re(N-O) plot, where the data are distributed more evenly. The maxima for Groups 3 and 4 are 1392 and 1402 cm -1 , considerable overestimations of 10% and 11% given by KMLYP and MGGA_MVSh, respectively. The Group 3 outlier with an ω3 minimum (1217 cm -1 ) much lower than the benchmark belongs to X1BK, which is consistent with the corresponding outlier in Figure .