Computational study of cation substitutions in apatites |
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Authors: | Toomas Tamm Merike Peld |
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Institution: | a Department of Chemistry, Tallinn University of Technology, Ehitajate tee 5, EE-19086 Tallinn, Estonia b Laboratory of Inorganic Materials, Tallinn University of Technology, Ehitajate tee 5, EE-19086 Tallinn, Estonia |
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Abstract: | Density-functional theory plane-wave modeling of fluor- and hydroxyapatites has been performed, where one or two calcium ions per unit cell were replaced with cadmium or zinc cations. It was found that cadmium ions favor Ca(1) positions in fluorapatites and Ca(2) positions in hydroxyapatites, in agreement with experiment. A similar pattern is predicted for zinc substitutions. In the doubly substituted cases, where only hydroxyapatites were modeled, a preference for the substituting ions to be located in Ca(2) position was also observed. Displacement of the hydroxide ions from their symmetrical positions on the hexagonal axis can be used to explain the preferred configurations of substituting ions around the axis. |
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Keywords: | Apatites Planewave calculations Ion migration Absorption |
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