Structures of barite (001) and (210)-water interfaces.
The structures of the barite (001) and (210) cleavage surfaces were measured in contact with deionized water at 25 {sup o}C. High resolution ({approx}1 {angstrom}) specular X-ray reflectivity and atomic force microscopy were used to probe the step structures of the cleaved surfaces and the atomic structures of the barite-water interfaces including the structures of water near the barite-water interfaces. The barite (001) and (210) cleavage surfaces are characterized by large (>2500 {angstrom}) domains separated by unit-cell steps (7.15 and 3.44 {angstrom} steps for the (001) and (210) surfaces, respectively). This observation was unanticipated for the (001) surface in which adjacent BaSO{sub 4} layers are displaced vertically by c/2 and symmetry related through a 2{sub 1} screw axis along (001). The atomic structures of the two cleavage surfaces derived by X-ray reflectivity reveal that near-surface sulfate groups exhibit significant ({approx}0.4 {angstrom}) structural displacements, while Ba surface ion displacements are significantly smaller ({approx}0.07 {angstrom}). Water adsorbs to the barite surfaces in a manner consistent, in both number and height, with the saturation of broken Ba-O bonds; no evidence was found for additional structuring of the fluid water near the surface.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 943241
- Report Number(s):
- ANL/ER/JA-38560; JPCBFK; TRN: US200916%%607
- Journal Information:
- J. Phys. Chem. B, Vol. 105, Issue 34 ; Aug. 30, 2001; ISSN 1089-5647
- Country of Publication:
- United States
- Language:
- ENGLISH
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