TUNNELING DYNAMICS IN WATER TETRAMER AND PENTAMER

We present a theoretical study of the structures, energetics and tunne ling dynamics of the cyclic water tetramer and pentamer, both of which have recently been observed experimentally. The very good agreement b etween vibrationally averaged rotational constants from diffusion quan tum Monte Carte calculations and experimental values confirms that the structures are cyclic. We calculate a splitting for a tunneling motio n that is a likely cause for doublets observed experimentally in the f ar infrared spectrum of (D2O)(4). Predictions of tunneling splittings yet to be observed in the water pentamer are made. (C) 1996 American l nstitute of Physics.