• Other methods including TPM, GTPM, FCHM, and XCHM afford larger errors and cannot be recommended, despite their continued widespread use. For example, the smallest MAE that we are able to achieve with XCHM (over all of the XC functionals that were tested) is 1.6 eV using SCAN, which is much larger than the ∆SCF error of 0.3 eV that is obtained using the same functional. For TPM the smallest MAE is 2.9 eV (using B3LYP), for GTPM it is 2.2 eV (again using B3LYP), and for FCHM it is 1.8 eV (in conjunction with BH&HLYP). In each case, this is significantly larger than the corresponding ∆SCF error.