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Formation energies and site preference of substitutional divalent cations in carbonated apatite
Author(s) -
Saito Tatsushi,
Yokoi Tatsuya,
Nakamura Atsutomo,
Matsunaga Katsuyuki
Publication year - 2020
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.17263
Subject(s) - divalent , apatite , coordination number , crystallography , chemistry , bond length , phosphate , ion , inorganic chemistry , crystal structure , mineralogy , organic chemistry
First‐principles calculations were performed to examine defect formation energies and site preference of substitutional divalent cations M 2+ (M = Mg, Cu, Zn, Cd, Sr, Pb, and Ba) in hydroxyapatite (HAp, Ca 10 (PO 4 ) 6 (OH) 2 ) and carbonated apatite (CAp). All inequivalent substitutional sites of CO 3 2 -and M 2+ were investigated to determine their most preferential sites. For all M 2+ studied, their defect formation energies for the most stable substitutional sites were lower in CAp than in hydroxyapatite (HAp), demonstrating that M 2+ are preferentially substituted into CAp over HAp. For Ca sites in CAp, correlations between the defect formation energies and Ca‐O bond lengths showed that bigger and smaller M 2+ than Ca 2+ are preferentially substituted for Ca sites with longer and shorter bond lengths than those in HAp, respectively. In addition, Ca sites with lower coordination numbers than 6 are preferentially substituted by Zn 2+ and Cu 2+ that originally tend to form 4‐ or 5‐fold coordination in their phosphate crystals. CO 3 2 -substitution is therefore likely to effectively stabilize substitutional foreign ions by modifying bond lengths and coordination numbers of Ca sites from those in pure HAp. These effects may play an important role in enhancing the M 2+ solubility into CAp.