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The effect of barium on calcite {101#4} surfaces during growth

Astilleros García-Monge, José Manuel and Pina Martínez, Carlos Manuel and Fernández Díaz, Lourdes and Putnis, Andrew (2000) The effect of barium on calcite {101#4} surfaces during growth. Geochimica et cosmochimica acta, 64 (17). pp. 2965-2972. ISSN 0016-7037

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Abstract

In situ atomic force microscopy (AFM) experiments have provided information about the effect
of Ba21 on crystal growth of calcite {101#4} surfaces. The microtopographic features observed have been
interpreted by considering both the structural control that the calcite surfaces exert on the incorporation of
divalent cations and the supersaturation state of the solution used. Pinning of the calcite growth steps occurs
at low Ba concentrations, suggesting specific sites for Ba incorporation. When the Ba content of the solution
is increased the advancement of monomolecular steps is observed. Although [4#41]1 and [481#]1 steps advance
showing characteristic jagged edges, the parallel steps (i.e., [4#41]2 and [481#]2) remain practically immobile.
This fact can be explained by considering the nonsymmetrically related distribution of large and small sites
along the calcite steps and the easier incorporation of barium on the former. The measured increase in the
height of the newly grown steps is also consistent with such preferential incorporation of Ba in certain
positions. A further increase in the Ba concentration of the solutions leads to the formation of bidimensional
nuclei on the calcite {101#4} surfaces. The nature of these nuclei is discussed taking into account the
supersaturation of the solution with respect to two possible structures that can accommodate Ba: the
calcite-type structure and the aragonite-type structure.


Item Type:Article
Uncontrolled Keywords:Crystal growth; Calcite; Barium
Subjects:Sciences > Geology > Crystallography
ID Code:14533
Deposited On:07 Feb 2012 12:56
Last Modified:07 Feb 2012 12:56

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