HR: 1340h
AN: B33C-1438    [Abstracts]
TI: Surface Energetics of Calcite {10-14} Faces upon the Adsorption of succinic Acid
AU: * Hu, Q
EM: qiaona@umich.edu
AF: Department of Geological Sciences, University of Michigan, 2534 C.C. Little Building,1100 N. University Ave., Ann Arbor, MI 48109, United States
AU: Teng, H
AF: Department of Chemistry, George Washington University, Washington, D.C. 20052, Washington, D.C, 20052, United States
AU: Biswas, S
AF: Department of Geological Sciences, University of Michigan, 2534 C.C. Little Building,1100 N. University Ave., Ann Arbor, MI 48109, United States
AU: Becker, U
EM: ubecker@umich.edu
AF: Department of Geological Sciences, University of Michigan, 2534 C.C. Little Building,1100 N. University Ave., Ann Arbor, MI 48109, United States
AB: Interactions of calcite with carboxylic acids occur widely and play an important role in many natural processes such as biomineralization and metal ion sequestration. The main contributor to the adsorption energy is the electrostatic interaction between the deprotonated carboxylic group of the organic acid and Ca2+ ions on the mineral surface. Although a number of experimental studies have identified the distribution of adsorption sites on calcite, the energetics of the surfaces of this mineral and the orientation of the organic molecules after the adsorption is still poorly understood. We have used empirical-potential methods to calculate calcite step energies for different step directions on {10-14} surfaces. In the presence of succinic acid (SUC), the less common and polar [421] and [010] directions develop and are shown to be more stable than the periodic bond chain directions. Three different adsorption cases were tested for each step: (i) one SUC molecule in the center of the step, (ii)a neutral SUC molecules chain along the step, (iii) a deprotonated SUC molecules chain along the step. These results indicate that SUC stabilizes steps in the directions parallel to [421] and [010] by lowering the step free energies. Adsorption energies of SUC were calculated along different kinds of steps with decreasing numbers of SUC molecules. The results showed a positive correlation between the number of SUC molecules and the stability of steps along [421] and [010] directions, and an insignificant dependence of step stability upon the amount of SUC molecules for cleavage directions.
DE: 0400 BIOGEOSCIENCES
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
DE: 0419 Biomineralization
DE: 0430 Computational methods and data processing
DE: 0466 Modeling
SC: Biogeosciences [B]
MN: 2007 Fall Meeting