HR: 0830h
AN: B21B-0705    [PDF]
TI: Molecular Structure of Water Absorbed on a Mica Surface
AU: * Park, S
EM: Sungho_Park@lbl.gov
AF: Geochemistry Department, Earth Sciences Division, Lawrence Berkeley National Laboratory, Mail Stop 90/1116, 1 Cyclotron Rd., Berkeley, CA 94720
AU: Sposito, G
EM: GSposito@lbl.gov
AF: Geochemistry Department, Earth Sciences Division, Lawrence Berkeley National Laboratory, Mail Stop 90/1116, 1 Cyclotron Rd., Berkeley, CA 94720
AB: The molecular structure of water adsorbed on micaceous minerals (2:1 layer-type aluminosilicates) has long been of widespread interest because of its crucial role in geochemical and biological processes. Early conceptualization of this structure imputed to it an icelike character because of its longer relaxation times when compared to bulk liquid water and its potential for epitaxy with the hexagonal array of oxygen atoms on the basal surfaces of mica and 2:1 clay minerals. These speculations have received support periodically from experimental and modeling studies, but recent spectroscopic data suggest that the hydration water on micaceous minerals is more disordered and more labile than ice Ih. Monte Carlo simulations of hydration water on the mica (001) surface under ambient conditions revealed water molecules bound closely to the ditrigonal cavities in the surface, with a lateral distribution of approximately one per cavity, and water molecules (interposed between $K^{+}$ counter ions) in a layer situated about 2.5$\AA$ from a surface O along a direction normal to the (001) plane. The calculated water O density profile was in quantitative agreement with recent x-ray reflectivity measurements indicating strong lateral ordering of the hydration water but liquidlike disorder otherwise.
UR: http://www-esd.lbl.gov/GEO/aqueous_geochem/index.html
DE: 0400 Biogeosciences
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
DE: 1099 General or miscellaneous
SC: Biogeosciences [B]
MN: 2003 Fall Meeting