Water clusters in a confined nonpolar environment

The stability and structure of water clusters in a confined nonpolar environment is investigated theoretically by examining the encapsulation of water molecules inside a fullerene (C₆₀) cage. While the Hartree–Fock (6-31G) calculations suggest H₂O@C₆₀ to be marginally more stable (−0.5 kcal/mol) than the isolated water and C₆₀ molecules, second order Møller–Plesset perturbation theory suggests it to be much more stable (−9.9 kcal/mol). It is shown that encapsulation results in the breaking of hydrogen bonds and rearrangement of water clusters. The tetramer inside the cage, for example, is tetrahedral in arrangement, in contrast to a square planar geometry observed in the gas phase.