title: Modeling water exchange on an aluminum polyoxocation.
abstract: For the first time, water exchange on a polymeric complex has been modeled using a combination of gas-phase ab initio calculations and molecular dynamics (MD) simulations. The GaO4Al12(OH)24(H2O)12(7+)aq ion (GaAl12) was chosen because high-quality experimental data exist, including an activation enthalpy (+63 +/- 7 kJ/mol) and an activation volume (+3 +/- 1 cm3/mol). We took a two-step approach. First, the local solvent structure and the initial states for reaction were inferred from the molecular dynamics simulations. Second, we used this information to evaluate initial-state structures in the ab initio calculations. The energy differences between the initial and transition states from the ab initio calculations varied from +59 kJ/mol to +53 kJ/mol depending upon details, closely approximating the activation enthalpy.
authors.affiliation: Department of Geology and Department of Chemistry, University of California, Davis, California 95616, USA. andrew.stack@eas.gatech.edu
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Stack
authors.forename: James R
authors.initials: JR
authors.lastname: Rustad
authors.forename: William H
authors.initials: WH
authors.lastname: Casey