Superfund Research Program

Computational Core (ARRA Funded)

Project Leader: Randall W. Hall (Dominican University of California)
Grant Number: P42ES013648
Funding Period: 2009-2011

Project-Specific Links

Final Progress Reports

Year:   2010 

The Computational Core supports the research projects through expertise and training, software, and workstations for students to model the properties of ultrafine particles, environmentally persistent free radicals, chlorinated hydrocarbons, and brominated hydrocarbons. The thermodynamics and kinetics of elementary reactions, electronic structures of products, reactants, and transition states, and particle growth pathways are being examined. The Core’s focus in the first year has been on 1-10 nm clusters of iron oxide because it is well established that iron oxide nanoparticles will catalyze the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans from various precursors. The researchers’ goal is to understand the geometric structure of these clusters and how the clusters evolve with growing cluster size.

The redox potential of small clusters of Fe_nO_x are of interest because Core researchers believe that the ability of a metal to be reduced with the concomitant formation of the surface-associated free radical may be the key step in forming persistent free radicals. They have found the lowest energy spin states and geometric structures for FeO, Fe₂O₂, Fe₂O₃, and Fe₃O₃. The search for the lowest energy spin state typically involves geometry optimizations of at least three different spin states. The researchers are currently studying the reactions of these clusters with water and phenol. It appears that addition of water may break a Fe-O bond (in the larger clusters) and creates an Fe-OH and an –OH moiety. These results will be analyzed to determine the most and least stable (with respect to reaction with phenol and substituted phenols) of the FeO clusters as well as the reaction sites and change in oxidation state of the metal atoms. These results will be combined with experimental studies to probe the mechanism of polychlorinated dibenzo-p-dioxins and dibenzofurans formation.