Characterization of low-barrier hydrogen bonds 2. HF 2−: a density functional and ab initio study

Abstract

Hartree-Fock, Moller-Plesset, QCISD, CCSD, and DFT calculations have been carried out using the 6–31+G(d,p), 6–31+G(2d,p), 6–31+G(3d,2p), and 6–31+G(3df,2p) basis sets to study the interaction of a fluoride ion with hydrogen fluoride. In each case the resulting hydrogen bond is extremely strong, resulting in a single well potential, with no barrier for proton transfer. Density functional methods employing non-local gradient-corrected exchange and correlation functionals were found to perform very similarly to other correlated methods, including calculations at the MP2, QCISD, and CCSD levels of theory. DFT calculations using the local functional SVWN gave results in very poor agreement with the other methods. SVWN gave interaction energies about 10 kcal mol −1 too high when compared to recent gas phase experiments.