Knowledge Bank

Efforts are being made in this laboratory to study hydrogen (H) bonding in several particularly well suited H-bonded compounds for which experimental data and theoretical model calculations are known and reported. The bifluoride ion, $HF2-$, and the dihydrated proton $H5O2+$, are the first of a series for which studies have been completed, and other species are currently under investigation. Objectives of the studies are first of construct the best possible” two-dimensional potential surface corresponding to the linear displacements of X-H...X internuclear coordinates. This is done using a semi-empirical model potential in which spectroscopic, thermodynamic and structural data are fitted to the function directly. Then additional parameters in the function are used to fit ab intitio calculations, fixing the ‘shape” of the potential surface in the region near the bottom of the potential well. This results in a demonstrably realistic potential function that we feel is accurate over the entire domain of usual chemical interest, XHX, XH + X and X + H + X. Secondary objectives of these studies are to calculate the vibrational eigenfunctions and eigenvalues for the proton, H, or deuteron, D. In this procedure, we use the approximation of clamped” heavy nuclci, a separation of motion between the H atom and the terminal X atoms. This procedure results in a total energy configuration of the H bond allowing one to reminimize the energy of the ground state (taking zero-point energies into account) and to postulate new dynamic pathways of the excited vibrational states.