Doctor of Philosophy, The Ohio State University, 2009, Chemistry

To date, fifteen phases of ice have been discovered. Many of these phases occur in pairs consisting of a fully ordered member and a hydrogen bond (H-bond) disordered phase. The disordered phase contains the water oxygens in nearly the same positions as the fully ordered phase, but the orientations of hydrogens are disordered. Our research examines the phase transitions between members of these ordered/disordered pairs. These transitions are sluggish because they occur at such low temperatures that water molecules cannot easily rotate to rearrange the directions in which the hydrogen bonds point. It is defects in the ice lattice that make the transitions possible. For instance, ice Ih transforms to ice XI only when doped with hydroxide ions, but many questions linger about the mechanism since experiments suggest that hydroxide ions are not mobile near the transition temperature. In this dissertation, theoretical methods are introduced which are capable of describing the small energy differences among the innumerable H-bond configurations of the water molecules in ice. The theory uses input from periodic electronic density functional theory calculations for small unit cells to parameterize interactions in terms of the H-bond topology. This parameterization enables statistical mechanical calculations for systems large enough to approximate the thermodynamic limit. Our calculations were the first to confirm that ordinary ice, a disordered phase, transforms into a fully ordered counterpart, ice XI. For those disordered phases for which an ordered version has been experimentally characterized, our methods yield transition temperatures in good agreement with experiment. We also proposed a candidate structure to experimentalists for proton-ordered ice VI, for which an ordered version has yet to be observed. We have also extended these methods to describe the interactions of the H-bond topology with defects (ionic and orientational) and oxygen site-disorder. We have successf (open full item for complete abstract)

Committee: Sherwin J. Singer PhD (Advisor); James V. Coe PhD (Committee Member); Russell M. Pitzer PhD (Committee Member) Subjects: Chemistry