Naturally occurring surfaces that exhibit structural iron in different oxidation states are known to be capable of heterogeneous reduction/oxidation (redox) reactions, and this reactivity influences the transport and fate of redox active aqueous contaminants. To date, little molecular-level understanding of this class of geochemical reactivity is available. The main objective of the current study is to obtain structural, electronic and thermodynamic characterization of the oxidized and reduced iron-bearing clay surfaces. We are particularly interested the edge-surface (110) of NAu-1. Several ratios of Fe(II)/Fe(III) in the structure of NAu-1 are studied in the realm of density functional theory (DFT) and employing a Hubbard U term to treat the strongly correlated Fe d states. In the style of Reuter et al., the DFT results are used in a thermodynamics framework to calculate surface free energies across ambient temperature and pressure conditions.

First principles characterization of nontronite clay surfaces with varying Fe(II)/Fe(III) composition

249th National Meeting (2015)

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