15min:

SHERWIN J. SINGER, LARS OJAMÄE AND ISAIAH SHAVITT, Department of Chemistry, Ohio State University, Columbus, OH 43210.

Our recent progress in the study of protonated and neutral water clusters, (H₂O)_nH⁺ AND (H₂O)_n , is reviewed. Both variational and diffusion Monte Carlo calculations have been performed, leading to a prediction of the fundamental frequency for motion of the central proton in H₅O₂⁺. Ab initio\/ electronic structure calculations suggest this absorption feature will be intense. Extensive Monte Carlo simulations of larger hydrated proton clusters indicate there is a transition between compact and extended phases. Local minima of the potential energy surface for (H₂O)_nH⁺ AND (H₂O)_n are studied. The number of topologically distinct hydrogen-bonded arrangements can be enumerated using graph theory, leading to a prediction of the number of distinct local minima of the potential energy surface in compact geometries, including dodecahedral clathrate structures.