is the approximation to the protein-ligand interaction energy obtained with MFCC [Eq. ( )] Comparison of the error in the protein-ligand interaction energy (ADF/BLYP/DZP) for the conventional MFCC method and the MFCC-MBE(2) method for a test set of seven protein-ligand complexes. We include results both with a COSMO solvation model using ε = 4 and ε = 78.39 (water).