Global potential energy minima of SPC/E water clusters without and with induced polarization using a genetic algorithm

The global minimum potential energy structures of water clusters, (H2O)(n), n = 2-14, have been calculated for the SPC/E (Simple Point Charge/Extended ) model and a recent fluctuating charge version of the latter using a simpl e genetic algorithm. The SPC/E cluster geometries are in good agreement wit h previous TIP3P (Transferable Intermolecular Potential-3 Point) and TIP4P (Transferable Intermolecular Potential-4 Point) calculations as well as the interpretation of experimental measurements. In contrast to this, the pola rizable version of the SPC/E model, which is based on the fluctuating charg e approach, deviates rather strongly for n = 6 with few exceptions. However , comparing the polarizable model to ab initio results for identical cluste r geometries we find reasonable agreement for the magnitude of the average molecular dipole moment, the corresponding energy per molecule, and the ave rage oxygen-oxygen distance as functions of n.