Date/Time
Date(s) - 06/10/2004
3:30 pm - 4:30 pm

Title: Hydrogen Bond Topology in Water Clusters and Ice

Speaker: Dr. Sherwin Singer

Institute: Department of Chemistry, Ohio State University

Location: ABB 102

Description:

The energetics of water clusters and ice have long been conjectured to be correlated with topological properties of the hydrogen bond network. We have developed a procedure for systematically correlating physical properties with the hydrogen bond topology of water clusters and ice. Together with periodic density functional theory calculations, this leads to a prediction of proton ordering phase transitions in ice. We validate our methods by application to the ice VII/VIII phase transition, which is well-characterized experimentally. We then study the proton ordering phase transition in ice Ih, which has been the subject of some debate.

Aspects of neutral and protonated water clusters will be discussed. A compact-to-extended phase transition in protonated water clusters has been identified. Also, we have studied the hydrogen bond arrangements of a dodecahedral cluster of 20 water molecules. The hydrogen bond topology has a strong effect on the energetics of this cluster, and even on its chemical properties. In fact, some H-bond arrangements spontaneously autoionize to form a zwitterionic structure with spatially separated excess proton and hydroxide.