NUCL 16 |
| We carried out electronic structure calculations on adsorption complexes of uranyl(VI) at the surfaces of corundum and kaolinite. A periodic supercell approach was applied in the framework of density functional theory using the projector augmented wave method. For the adsorption of uranyl(VI) on the hydroxylated surface of α-Al2O3(0001) we compared inner- and outer-sphere complexes. Solvation effects were taken into account by explicitly treating the first solvation shell of uranyl while long-range electrostatic effects were estimated by comparison with molecular models. For the defect-free surface, outer-sphere complexation is preferred by about 70 kcal/mol [L. V. Moskaleva, V. A. Nasluzov, N. Roesch, Langmuir 22 (2006) 2141]. Compared to the bulk structure, OH groups were determined to be tilted on the octahedral surface of kaolinite. In agreement with other calculations, surface relaxation effects were calculated to be minor. The interaction of kaolinite surfaces with water was investigated up to coverages of more than a monolayer. While the octahedral surface yields strong hydrogen bonds to the water overlayer, the interaction with the tetrahedral surface was determined to be weak, as expected. We compared inner- and outer-sphere complexes of uranyl(VI) at both surfaces of kaolinite, for different models of charge compensation and for various surface defects. Finally, we compared our results to experimental data for clay minerals. |
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Computational Actinide and Transactinide Chemistry: Progress and Perspectives
8:10 AM-12:00 PM, Sunday, August 19, 2007 Boston Park Plaza -- Franklin Rm, Oral
Division of Nuclear Chemistry & Technology |