Abstract: Ab initio molecular orbital calculations including MP2 correlation energy was employed to optimize the geometries of the hydrogen-bonded complexes formed by HCN(HNC) with NH₃, H₂O and HF, respectively at aug-cc-pVTZ level. It was found that there were two kinds of stable complexes bonded by intermolecular hydrogen bonds: HCN(HNC) as the proton donor and as the proton acceptor. The effect of basis set superposition error on the total interaction energy is smaller than 3.34 kJ/mol. Natural bond orbital (NBO) analysis was performed to analyze the atomic charges and charges transfer in the monomers and complexes. The results of the decomposition of interaction energy according to SAPT2 show that the electrostatic and induction forces dominate the intermolecular interaction, and there is a good correlation between induction forces and charges transfer.

Key words: HCN(HNC), Intermolecular interaction, Basis set superposition error(BSSE), Natural bond orbital(NBO), Symmetry adapted perturbation theory(SAPT)