Theoretical study of the cage water hexamer structure

We present a theoretical examination of the structures and dynamics of a ''cage'' form of the water hexamer which has recently been observed experimentally. A thorough examination with one of the best many-body water potentials is used to characterize minima, transition states, and reaction paths. All of the rearrangements characterized have pathways similar to those already seen for the water dimer and trimer. The accuracy of this empirical potential is assessed by comparison with MP2 optimizations, and good agreement in terms of the topology of the intermolecular potential energy surface is seen. Quantum simulation using the diffusion quantum Monte Carlo method is used to show that the ground state wave function is dominated by one minimum in the water hexamer potential.