%0 Journal Article
%T Periodic density functional theory calculations of bulk and the (010) surface of goethite
%A James D Kubicki
%A Kristian W Paul
%A Donald L Sparks
%J Geochemical Transactions
%D 2008
%I BioMed Central
%R 10.1186/1467-4866-9-4
%X Calculations of the bulk mineral structure accurately reproduced the observed crystal structure and vibrational frequencies, suggesting that this computational methodology was suitable for modeling the goethite-water interface. Energy-minimized structures of bare, hydrated (one H2O layer) and solvated (three H2O layers) (010) surfaces were calculated for 1 ¡Á 1 and 3 ¡Á 3 unit cell slabs. A good correlation between the calculated and observed vibrational frequencies was found for the 1 ¡Á 1 solvated surface. However, differences between the 1 ¡Á 1 and 3 ¡Á 3 slab calculations indicated that larger models may be necessary to simulate the relaxation of water at the interface. Comparison of two hydrated surfaces with molecularly and dissociatively adsorbed H2O showed a significantly lower potential energy for the former.Surface Fe-O and (Fe)O-H bond lengths are reported that may be useful in surface complexation models (SCM) of the goethite (010) surface. These bond lengths were found to change significantly as a function of solvation (i.e., addition of two extra H2O layers above the surface), indicating that this parameter should be carefully considered in future SCM studies of metal oxide-water interfaces.Goethite (¦Á-FeOOH) is a common and reactive mineral in the environment [1]. ¦Á-FeOOH is the most thermodynamically-stable form of the Fe-oxyhydroxides found in soils, groundwater, and acid mine drainage precipitates [2]. ¦Á-FeOOH is an excellent adsorbent of contaminants (e.g., arsenate) and nutrients (e.g., phosphate) and is an electron receptor for anaerobic bacterial respiration under anoxic conditions ([3,4] and references therein). Consequently, the surface chemistry of ¦Á-FeOOH is important for understanding many environmental processes. One of the most stable and well-studied low-index surfaces of ¦Á-FeOOH is the (010) surface (Pbnm space group = (100) in the Pnma space group; [5,6]). As a result, this study will focus on the (010) ¦Á-FeOOH surface.Several molecular mo
%U http://www.geochemicaltransactions.com/content/9/1/4