BASIS-SETS FOR MOLECULAR-INTERACTIONS .4. ENERGY DECOMPOSITION ANALYSIS

The performance of a variety of basis sets in evaluating components of the interaction energy in the HF dimer was systematically examined. It is shown that simple modification of the standard 6-31G(d,p) basis set can accurately portray the components of the interaction energy. The best results are obtained when the modifications include reoptimization of the orbital exponents within the framework of the relevant molecules, plus addition of a single diffuse shell of sp orbitals on the non-hydrogen centres and two sets of d functions. The energy decomposition procedure was applied to hydrogen-bonded complexes of simple hydrides to analyse the factors leading to the formation of the hydrogen bond.