Using ab initio calculations, the geometries, interaction energies and bonding properties of chalcogen bond and halogen bond interactions between YOX4 (Y = S, Se; X=F, Cl, Br) and NH3 molecules re studied. These binary complexes are formed through the interaction of a positive electrostatic potential region (σ-hole) on the YOX4 with the negative region in the NH3. The ab initio calculations are carried out at the MP2/aug-cc-pVTZ level, through analysis of molecular electrostatic potentials, quantum theory of atoms in molecules and natural bond orbital methods. Our results indicate that even though the chalcogen and halogen bonds are mainly dominated by electrostatic effects, but the polarization and dispersion effects also make important contributions to the total interaction energy of these complexes. The examination of interaction energies suggests that the chalcogen bond is always favored over the halogen bond for all of the binary YOX4:NH3 complexes.
