Many-body effects in tetrahedral water clusters

Many-body contributions to the energies, forces, electron densities, dipole moments, and Mulliken charges for a water molecule bound in a tetrahedral environment have been calculated by ab initio SCF methods. An (H2O)5 and two ⊕2+2⋅H2O complexes have been investigated. Nonadditive effects in the energies can to a large part be explained on the basis of the electron redistribution for interacting pairs, while nonadditive effects in the electron rearrangement were found to be small. Four- and five-body corrections to all the pentamer properties calculated were found to be small.