We can see from Fig. (b) that for the TMB cases, when DM21 does not converge, DM21@B3LYP is much more accurate than B3LYP@B3LYP. This intriguing improvement of DM21@B3LYP over B3LYP@B3LYP aligns with similar improvements observed for maingroup barriers 8 . On the other hand, this improvement in panel(b) (for TMB40 barriers that did not converge with DM21) is much larger than in panel (a) (cases that converge). This discrepancy suggests a potential