The Group 1 functional TH-FL gives a frequency closest to the benchmark (ω5 = 24 cm -1 ). The From the pruned subset of DFAs that produce a linear minimum (Table ), only two result in ω5 less than 100 cm -1 . The Group 3 meta-GGA TPSSh predicts ω5(π) = 52 cm -1 , whereas the ω5(π) = 33 cm -1 result from MN12-L (Group 1, GGA) is closest to the benchmark. However, MN12-L also produces a bent minimum with a total energy essentially indistinguishable from that of its linear structure, and ω5(a′) = 69 cm -1 for this bent form. The only other DFA in Table that produces an H-C-N bending frequency below 100 cm -1 is the Group 6 double-hybrid DSD-BLYP-D3(BJ), for which ω5(a′) = 84 cm -1 and the barrier to linearity (EB) is merely 0.23 cm -1 (Table ).