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dc.contributor.authorPinto, A.
dc.contributor.authorRuiz-Agudo, E.
dc.contributor.authorPutnis, Christine
dc.contributor.authorPutnis, Andrew
dc.contributor.authorJiménez, A.
dc.contributor.authorPrieto, M.
dc.identifier.citationPinto, A. and Ruiz-Agudo, E. and Putnis, C. and Putnis, A. and Jim�nez, A. and Prieto, M. 2010. AFM study of the epitaxial growth of brushite (CaHPO<inf>4</inf>� 2H<inf>2</inf>O) on gypsum cleavage surfaces. American Mineralogist. 95 (11-12): pp. 1747-1757.

The epitaxial overgrowth of brushite (CaHPO4·2H 2O) by the interaction of phosphate-bearing, slightly acidic, aqueous solutions with gypsum (CaSO4·2H2O) was investigated in situ using atomic force microscopy (AFM). Brushite growth nuclei were not observed to form on the {010} gypsum cleavage surface, but instead formed in areas of high dissolution, laterally attached to gypsum [101] step edges. During the brushite overgrowth the structural relationships between brushite (Aa) and gypsum (A2/a) result in several phenomena, including the development of induced twofold twining, habit polarity, and topographic effects due to coalescence of like-oriented crystals. The observed brushite growth is markedly anisotropic, with the growth rate along the main periodic bond chains (PBCs) in the brushite structure increasing in the order [101] > [101] > [010], leading to tabular forms elongated on [101]. Such a growth habit may result from the stabilization of the polar [101] direction of brushite due to changes in hydration of calcium ions induced by the presence of sulfate in solution, which is consistent with the stabilization of the gypsum [101] steps during dissolution in the presence of HPO2-4 ions. The coupling between growth and dissolution was found to result in growth rate fluctuations controlled by the changes in the solution composition.

dc.publisherMineralogical Society of America
dc.titleAFM study of the epitaxial growth of brushite (CaHPO<inf>4</inf>� 2H<inf>2</inf>O) on gypsum cleavage surfaces
dc.typeJournal Article
dcterms.source.titleAmerican Mineralogist
curtin.departmentDepartment of Chemistry
curtin.accessStatusFulltext not available

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