Study of the structure of molecular complexes. VI. Dimers and small clusters of water molecules in the Hartree-Fock approximation

Abstract

The analytical fit to a large number of Hartree-Fock computations for the water-water interaction has been reanalyzed and used to study small clusters of water molecules. With the analytically fitted Hartree-Fock potential, thousands of possible configurations for the dimers, trimers, tetramers, pentamers, hexamers, heptamers, and octamers of water have been compared in order to determine the configuration of lowest energy (maximal stabilization energy). For the dimer two possible stable configurations are found, corresponding to an open form and a cyclic form, with the open form being more stable. For the trimers and tetramers the cyclic forms are somewhat more stable than the open structures. For the larger clusters it is concluded that it is rather meaningless to consider a single structure, but what is physically relevant is the statistical distribution of different configurations, since many configurations with significantly different geometry have nearly the same energy. The comparison of the stabilization energy per molecule of the different clusters with the corresponding value for liquid water does not support the mixture-model theories of the structure of liquid water. Copyright © 1974 American Institute of Physics.