Monte Carlo simulation of F-(H2O)(4) using an ab initio potential

We present results concerning the structure and energetics of the cluster F -(H2O)(4) at 0 K, using high quality ab initio methods, and at a temperatur e of 300 K, using an ab initio Monte Carlo simulation. At 0 K, we find the global energy minimum corresponds to three waters solvating the fluoride io n and with the fourth water in an outer hydration shell, hydrogen bonding t o the other water molecules. Structures involving four waters hydrogen bond ing to the fluoride are, however, of only slightly higher energy. At 300 K, the simulation results indicate that the fluoride is mostly to be found wi thin a tetrahedron of solvating water molecules. The cluster is mobile, how ever, and a wide variety of structures are sampled. (C) 1999 American Insti tute of Physics. [S0021-9606(99)00208-1].