Abstract: The intermolecular complexes of BeH2 with hydrogen halides (HX(X=F, Cl, Br, I)) were examined using ab initio calculations performed at the second-order Moller-Plesset perturbation approximation with the 6-311++G(3d,3p) basis set. Dihydrogen-bonds were formed in complexes of BeH2 with hydrogen halides based on the judgement from the geometrical criteria. The characteristics of the bond critical points, the electron densities and their Laplacians, also confirmed this conclusion. The calculated binding energies of complexes of BeH2 with hydrogen halides usingMP2/6-311++G(3d, 3p) methods, corrected by the basis-set superposition error (BSSE) were -14.468 kJ·mol-1 to -5.464 kJ·mol-1. In an effort to comprehend the underlying basis of this interaction, we have also carried out a rigorous decomposition of the interaction energies using the symmetry adapted perturbational theory (SAPT) method. The results indicated that electro-static energies, induction energies, dispersion energies, and exchange-repulsion energies were all important to the total binding energies. The contribution of the induction energy to total attractive energy decreased from 37.8% in BeH2…HF complex to 24.0% in BeH2…HI complex. The dispersion energy dramatically increased from 16.0%in BeH2…HF complex to 33.8% in BeH2…HI complex.

Key words: Dihydrogen bonding, Symmetry adapted perturbation theory (SAPT), BeH2, Hydrogen halides