Dissociation Energy of the H 2 O···HF Dimer

Even though (H O) and (HF) are arguably the most thoroughly characterized prototypes for hydrogen bonding, their heterogeneous analogue H O···HF has received relatively little attention. Here we report that the experimental dissociation energy ( D ) of this important paradigm for heterogeneous hydrogen bonding is too large by 2 kcal mol or 30% relative to our computed value of 6.3 kcal mol . For reference, computational procedures similar to those employed here to compute D (large basis set CCSD(T) computations with anharmonic corrections from second-order vibrational perturbation theory) provide results within 0.1 kcal mol of the experimental values for (H O) and (HF) . Near the CCSD(T) complete basis set limit, the electronic dissociation energy for H O···HF is ∼4 kcal mol larger than those for (H O) and (HF) (∼9 kcal mol for the heterogeneous dimer vs ∼5 kcal mol for the homogeneous dimers). Results reported here from symmetry-adapted perturbation theory computations suggest that this large difference is primarily due to the induction contribution to the interaction energy.