THE PROBLEM OF SMALL NEGATIVELY IONIZED WATER CLUSTERS

structures of the negatively charged water clusters (H2O)(n)(-) with n up to 6 were optimized at the UHF/4-31 + + G* level without any geom etrical restriction. There was found a chainlike structure for the tri mer anion and both chainlike and cyclic geometries for the larger clus ters. According to the MP2 energy estimates, all the clusters with n g reater than or equal to 3 are more stable than the combinations of sep arated water molecules and a free electron. The energy of the cycles i s lower than that of the chains of the same size. However, the latter species are energetically closer to the neutral oligomers of the same geometry. The energy of vertical detachment of an electron from the ch ainlike hexamer anion is already about zero. Addition of a diffuse s f unction centered equidistantly between the oxygen atoms proved metasta bility, in particular, of the cyclic (H2O)(4)(-) structure. (C) 1997 J ohn Wiley & Sons, Inc.