H/D isotope effect on structures, binding energies, and basis set superposition errors in F−(H2O)n (n = 1–3) clusters

Abstract

The H/D isotope effects on structures, binding energies, and basis set superposition errors (BSSEs) of hydrated fluoride anion clusters, F−(H2O)n (n=1–3), are theoretically analyzed by using the MP2 level of multi-component molecular orbital (MC_MO-MP2) method, in which quantum nature of proton/deuteron and electron–electron correlation are directly taken account. Our results clearly show that the additional water molecule to F−(H2O)n−1 cluster forms stronger water–water hydrogen bond than that in simple water cluster, whereas the additional F−–water hydrogen bond formation in F−(H2O)n cluster weakens the original F−–water hydrogen bonds in F−(H2O)n−1 cluster. The BSSEs estimated in the MC_MO-MP2 calculations are slightly larger than those in the conventional MP2 calculations, due to the H/D geometrical isotope effect on the intermolecular distances. Consequently, the order of stability in several F−(H2O)3 cluster isomers cannot be adequately evaluated without BSSE corrections in our MC_MO-MP2 calculations, rather than the conventional MP2 ones.