On the quantum nature of an excess proton in liquid hydrogen fluoride

Abstract

Liquid hydrogen fluoride consists of chains of hydrogen-bonded molecules. The nature of an excess proton in liquid HF, which is of interest not only for its own sake, but also in relation to superacid chemistry and to its behavior in water, has been studied using computer simulations. The methodology employed is the density-functional-theory-based path-integral Car-Parrinello ab initio molecular dynamics. The excess proton, which formally exists as a H 2F+ or a H2F2+ defect in an HF chain, is found to strongly perturb the chain to which it is attached. Moreover, due to large zero-point energy, the charge defect is largely delocalized over several HF molecules.