Atomic-scale structure of the orthoclase (001)-water interface measured with high-resolution x-ray reflectivity.
In situ X-ray specular reflectivity and atomic force microscopy were used to determine the structure of the orthoclase (001) cleavage surface in contact with deionized water at 25{sup o}C. These are the first in situ measurements of the orthoclase-water interface structure performed to Angstrom-scale resolution. The orthoclase (001) cleavage surface has minimal roughness, and only one of two possible surface terminations is exposed. The X-ray data show that (1) the silica network at the orthoclase surface is terminated by an oxygen-containing species (e.g., O or OH) having a coverage of 1.9 {+-} 0.25 ML (the expected coverage is 2.0 ML, where 1 ML = 1 atom/55.76 {angstrom}{sup 2}), (2) the outermost layer of K{sup +} ions have been removed with a derived coverage of 0.0 {+-} 0.08 ML (the bulk truncated K{sup +} coverage is 1.0 ML), and (3) a complex relaxation profile affecting the near-surface structure propagates {approx}26 {angstrom} into the orthoclase with a maximum relaxation of {approx}0.15 {angstrom} near the surface. These data are inconsistent with K{sup +} ion depletion below the topmost K{sup +} layer. These results provide a new baseline for understanding the initial steps of the feldspar dissolution process, demonstrate the power of combining X-ray scattering techniques with scanning probe microscopies for understanding the intrinsic characteristics of complex mineral-water interface systems, and suggest a new approach for understanding feldspar dissolution mechanisms.
- 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:
- 942794
- Report Number(s):
- ANL/ER/JA-34678; GCACAK; TRN: US200922%%596
- Journal Information:
- Geochim. Cosmochim. Acta, Vol. 64, Issue 21 ; Nov. 2000; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- ENGLISH
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