GEOC 71 |
| Barry R. Bickmore, Department of Geology, Brigham Young University, P.O. Box 24606, Provo, UT 84602, Christopher J. Tadanier, Department of Geological Sciences and Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061, and Kevin M Rosso, Pacific Northwest National Laboratory, PO Box 999, K8-96, Richland, WA 99352. |
| A new method has been developed to predict acidity constants for oxyacids and oxide surface functional groups, combining bond-valence theory with ab initio molecular structure calculations. In the past, bond-valence methods for predicting acidity constants have neglected the effect of bond relaxation, which can be quite large. Therefore, we have calculated molecular structures of oxyacids and oxide surfaces using ab initio methods in order to estimate this effect. The unsaturated valence of oxygen on the conjugate base for a given acid-base reaction, divided among possible bonding orbitals, is linearly correlated to electrostatically corrected acidity constants for successive deprotonations of the same oxyacid. The slope of this correlation is nearly constant for all oxyacids, but the intercept varies with Me-O bond ionicity. The same method has been used to predict acidity constants on silica and gibbsite, with excellent success. |
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Interfacial Phenomena: Linking Atomistic and Macroscopic Properties
8:00 AM-11:40 AM, Tuesday, March 30, 2004 Marriott -- Marquis NW, Oral
Division of Geochemistry |