Exploring the relationships between anharmonicity and OH bond lengths in hydrogen bonded complexes

In this talk we explore the effects of anharmonicity on the zero-point averaged OH bond lengths in hydrogen bonded complexes. Clusters with as many as six HF molecules or water molecules are explored as well as protonated water clusters and complexes of water clusters with F$^-$, Cl$^-$, Br$^-$ and OH$^-$. It is shown that there is a universal correlation between the vibrationally averaged OH or HF bond length and the anharmonc OH or HF stretch frequency. This relationship provides an extension to previously investigated correlations between the equilibrium bond lengths and harmonic frequencies and allows one to anticipate OH or HF bond lengths based on measured frequencies. In addition, differences between the $R_z$ and $R_0$ structures are discussed within the context of these weakly bound complexes