Structures and Interaction Energies of Mixed Dimers of NH3, H2O, and HF by Hartree-Fock, Møller-Plesset, and Density-Functional Methodologies

Abstract

The intermolecular interaction energies for hydrogen-bonded complexes have been investigated using Hartree-Fock (HF), Møller-Plesset (MP2) and density functional theory (DFT). Interaction energies were computed for the following complexes: NH3--NH3, NH3--H2O, NH3--HF, H2O--H2O, H2O--HF, and HF--HF. Pople's split valence (6-31++G(2d,2p)) basis sets were employed throughout these calculations. The predicted interaction energies for these complexes using the B3-LYP hybrid method (without ZPE and BSSE) are: -4.02, -7.15, -14.26, -4.97, -9.30, and -4.73 kcal/mol, respectively. Charge transfer computed using the natural bond order (NBO) scheme suggests that the local density approximation tends to overestimate the amount of charge transferred between donor and acceptor when compared to MP2 results.