Top panel – NH₃ BE for a growing ΔR_LL and various low-levels of theory. The different series hold for a computational scheme following ONIOM(B3LYP-D3/6-311+G(d,p): x), where x , the low-level method, accounts for either for B3LYP-D3/growing basis set (see legend), or GFN2-xtb; Bottom panel – residue graph representing the relative difference between ONIOM(B3LYP-D3/6-311+G(d,p):GFN2-xtb) and ONIOM(B3LYP-D3/6-311+G(d,p): B3LYP-D3/growing basis set). Note that legends only explicit the low-level method of each series, for the sake of clarity. Lines do not represent any interpolated physical trends, they only serve as guides to highlight the trend and facilitate the reader view of the plots.