Atomic-scale imaging of calcite growth and dissolution in real time
- Univ. of California, Santa Barbara (United States)
- Pennsylvania State Univ., University Park (United States)
The authors present a new experimental technique for real-time observation of aqueous mineral growth and dissolution at the atomic scale using an atomic-force microscope (AFM) equipped with a flow-through fluid cell. They applied this technique to observe changes in surface topography on the (10{ovr 1}4) cleavage plane of calcite during alternating episodes of growth and dissolution. Growth occurred in a layer-by-layer fashion by the forward motion of monomolecular steps (0.3 {plus minus} 0.1 nm high) lying parallel to the edges of the cleavage face. Under all conditions studied, the velocities of positive (48{ovr 1}) and ({ovr 4}41) steps were the same; velocities of negative (48{ovr 1}) and ({ovr 4}41) steps were undetectably small, less than 0.1 nm s{sup {minus}1}. Steps were straight passing above perfect crystalline material, but roughened into two-dimensional dendrites above defective material. Dissolution nucleated shallow ({lt}5 nm deep) etch pinholes in defective material and faceted existing surface voids into {gt}90-nm-deep rhombic etch cores. Growth into these etch cores was impeded so that steps moved around them. AFM images of the surface atomic structure revealed rows of atoms along (010) spaced by 0.39 {plus minus} 0.05 nm with a periodicity along the rows of 0.43 {plus minus} 0.05 nm.
- OSTI ID:
- 7031701
- Journal Information:
- Geology; (United States), Journal Name: Geology; (United States) Vol. 20:4; ISSN GLGYB; ISSN 0091-7613
- Country of Publication:
- United States
- Language:
- English
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