and TPSSh are in better agreement than those of modB3LYP (aHF = 0.10) and M06-L (Pearson's r of 0.95 vs 0.55; Figure ). This could be expected as a result of better DGH-L agreement between the two functionals with fewer parameters (see Section 3.2). We also observe extreme outliers in T1/2 predictions of these functionals where T1/2 values are below 0 K or above 800 K (Supporting Information Figure and Table ). Negative T1/2 predictions, which are a result of either negative enthalpic (DH) or negative entropic (DS) spin splitting energies, are observed for ca. 21%