Characterization of water clusters in organic molecular hosts from density functional theory calculations

A density functional study of (H2O)(6) and (H2O)(8) clusters enclosed in organic hosts is undertaken. The calculations use supercells that contain up to 326 atoms. The crystal structures calculated for the (H2O)(6)/host and the (H2O)(8)/host systems are in qualitative agreement with those obtained from X-ray diffraction studies. The calculations confirm the presence of (H2O)(8) clusters with C-i symmetry in the (H2O)(8)/host crystal and verify the existence of one-dimensional chains of fused water hexamers within channels of the (H2O)(6)/host crystal. The major differences observed between the calculated and experimental structures are attributed to the limitations of the Perdew-Wang functional for describing long-range dispersion interactions.