MICROSCOPIC STUDY OF FLUORIDE WATER CLUSTERS

We have carried out ab initio calculations on the structure and energetics of F-(H2O)n, n = 1-6, clusters at the self-consistent mean-field (SCF) and second-order Moller-Plesset (MP2) levels of theory. The rather strong F-H2O interactions determine the strength of the hydrogen bonds between the water molecules and thus the structure of the clusters. Our data show that a transition from a predominant surface state to an interior state is observed at n = 4 and 5. By comparison with our previous calculations of other halide-water clusters, the strength of the halide-water interactions appears to be an important determining factor in the size at which a surface to interior transition is observed. The inclusion of zero-point energies and entropy corrections seems to reverse the energetic stability, making the interior states preferred over the surface states.