THEORETICALLY PREDICTED LOWEST-ENERGY STRUCTURES OF WATER CLUSTERS

Optimal geometries of finite atomic or molecular clusters are difficult to predict theoretically, because of the enormously large number of possible stable structures. In the present paper we use our recently proposed shift method to get the lowest-energy structures directly, without exploring the whole configurational space. The method deforms the original potential energy hypersurface by shifting the atom-atom components of the potential. As a result the whole system collapses into a single point. Then, by using the so-called reversing procedure the original potential is gradually rebuilt while the structure is optimized in each step. The reversing procedure leads to a kind of "big bang", because the molecules emerging from the collapse point gradually reacquire their original internal geometry, and at the same time the cluster geometry evolves to the final state corresponding to the original undeformed potential. This procedure has been applied to clusters containing M = 2,3,...10 water molecules and it turned out to produce, in all cases under study, structures of very low energy.