Dian Jiao

First Principles Calculations of Atomic Nickel Redox Potentials and Dimerization Free Energies: A Study of Metal Nanoparticle Growth.

The redox potentials and dimerization free energies of transient transition metal cations in water shed light on the reactivity of species with unusual charge states and are particularly pertinent to understanding the mechanism and feasibility of radiolysis-assisted metal nanoparticle growth from salt solutions. A combination of quasi-chemical theory and ab initio molecular dynamics thermodynamic integration methods are applied to calculate these properties for nickel. The reduction potential for Ni(2+) (aq) is predicted to be between -1.05 to -1.28 V, which is substantially lower than previous estimates. This suggests that Ni(2+) reduction may possibly occur in the presence of organic radical anion electron scavengers and hydrogen atoms, not just hydrated electrons. In contrast, Ni(+) is found to be stable against disproportionation. The formation of dimers Ni2 and Ni2(+) from Ni and Ni(+) are predicted to be favorable in water.

CO2 solvation free energy using quasi-chemical theory

Accumulation of greenhouse gases, especially carbon dioxide, is believed to be the key factor in global climate change. To develop effective ways to remove CO(2) from the atmosphere, it is helpful to understand the mechanism of CO(2) solvation first. Here we investigate the thermodynamics of CO(2) hydration using quasi-chemical theory. Two approaches for estimating hydration free energy are carried out. Both agree reasonably well with experimental measurements. Analysis of the free energy components reveals that the weak hydration free energy results from a balance of unfavorable molecular packing and favorable chemical association.

Structural Models and Molecular Thermodynamics of Hydration of Ions and Small Molecules

Abstract Solution equilibria are at the core of solvent-catalyzed reactions, solute separations, drug delivery, vapor partitioning and interfacial phenomena. Molecular simulation using thermodynamic integration or perturbation theory allows the calculation of these equilibria from parameterized force field models; however, the statistical many-body nature of solution environments inevitably complicates molecular interpretations of these phenomena. If our goal is molecular understanding in addition to prediction, then the statistical thermodynamic theories designed for mechanistic insight from structural analyses are especially important. In this report, we survey recent advances in the thermodynamic analysis of rigorous local structural models based on chemical structure.

Chemical Solvation of Ions and Small Molecules: Local Thermodynamic Models.

Abstract Solution equilibria are at the core of solvent-catalyzed reactions, solute separations, drug delivery, vapor partitioning and interfacial phenomena. Molecular simulation using thermodynamic integration or perturbation theory allows the calculation of these equilibria from parameterized force field models; however, the statistical many-body nature of solution environments inevitably complicates molecular interpretations of these phenomena. If our goal is molecular understanding in addition to prediction, then the statistical thermodynamic theories designed for mechanistic insight from structural analyses are especially important. In this report, we survey recent advances in the thermodynamic analysis of rigorous local structural models based on chemical structure.

Chapter Four – Structural Models and Molecular Thermodynamics of Hydration of Ions and Small Molecules

Abstract Solution equilibria are at the core of solvent-catalyzed reactions, solute separations, drug delivery, vapor partitioning and interfacial phenomena. Molecular simulation using thermodynamic integration or perturbation theory allows the calculation of these equilibria from parameterized force field models; however, the statistical many-body nature of solution environments inevitably complicates molecular interpretations of these phenomena. If our goal is molecular understanding in addition to prediction, then the statistical thermodynamic theories designed for mechanistic insight from structural analyses are especially important. In this report, we survey recent advances in the thermodynamic analysis of rigorous local structural models based on chemical structure.