QM evaluation of the TbPTR1 subpocket C reveals sensitivity of binding energies to positions of halogen phenyl substituents. In subpocket C, halogens on tail phenyls may form halogen bonds (Fig. ), which are poorly described by classical molecularmechanics force fields. Therefore, we investigated the effects of halogen substitutions in the 3,4-dichlorophenyl moiety, positioned as in I in the TbPTR1 pocket, on its binding energy to TbPTR1 using the computationally efficient QM-based model of ligand-protein interaction energy . This non-empirical QM model consists of two long-range interaction energy terms -multipole electrostatic energy (E