SIMULATIONS OF H2O SOLID, LIQUID, AND CLUSTERS, WITH AN EMPHASIS ON FERROELECTRIC ORDERING TRANSITION IN HEXAGONAL ICE

Simulations are presented of H2O ice, liquid, and clusters (H2O)(n) n less than or equal to 7. The first part is devoted to orientational en ergetics of ice. Ordinary hexagonal ice is orientationally disordered; a transition to an ordered form lice XI) can be induced at 72 K. The recently demonstrated ferroelectric structure of ice XI (Jackson, S. M .; Wield, V. M.; Whitworth, R. W.; Oguro, M.; Wilson, C. J. Phys. Chem . B 1997, 101, 6142) seems to contradict our understanding of H2O ... H2O interactions. A polarizable water potential is proposed that accou nts qualitatively for the existence of ferroelectric ice XI; its cruci al ingredient is the location of the polarizability center. This poten tial is then tested in classical trajectory simulations of water struc ture, energetics, selfdiffusion, and dielectric constant. Cluster ener getics and rotational constants are calculated using the rigid body di ffusion Monte Carlo technique.