DFT investigation of structural and vibrational properties of type B and mixed A-B carbonated hydroxylapatite

In nature, hydroxylapatite [Ca10(PO4)6(OH)2] is mostly present with various stoichiometric defects. The most abundant is the carbonate ion that can occupy different crystallographic sites (namely A and B types), however, its effects on the apatite structure is still an object of debate. Type A carbo...

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Bibliographic Details
Published inThe American mineralogist Vol. 99; no. 1; pp. 117 - 127
Main Authors Ulian, Gianfranco, Valdre, Giovanni, Corno, Marta, Ugliengo, Piero
Format Journal Article
LanguageEnglish
Published Washington Mineralogical Society of America 01.01.2014
Walter de Gruyter GmbH
Subjects
apatite
B3LYP
carbonate ion
Combinatorics
Crystal structure
Crystallography
density functional theory
DFT
Fourier transforms
FTIR spectra
Geometry
hydroxylapatite
infrared spectra
lattice parameters
Mineralogy
nonsilicates
numerical analysis
phosphates
Simulation
space groups
spectra
stoichiometry
structure
substitution
type A-B carbonated (hydroxyl) apatite
Type B carbonated hydroxylapatite
unit cell
vibrational spectra
X-ray diffraction data
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Summary:In nature, hydroxylapatite [Ca10(PO4)6(OH)2] is mostly present with various stoichiometric defects. The most abundant is the carbonate ion that can occupy different crystallographic sites (namely A and B types), however, its effects on the apatite structure is still an object of debate. Type A carbonated apatite was quantum mechanically simulated in a previous study, here we extend the simulation to bulk structural and vibrational features of Na-bearing type B and mixed type A-B carbonated hydroxylapatite [Ca10-xNax(PO4)6-x(CO3)x+y(OH)2(1-y), space group P1]. The simulation has been performed by ab initio density functional methods. The geometry of the models (lattice parameters and internal coordinates) have been fully optimized exploring different positions of the sodium ion in the apatite unit cell. The results, in agreement with XRD data, suggest that in each crystallographic cell in the biological mineral there is at least one calcium ion substitution or vacancy per cell. The carbonate ion presence in the apatite structure is in good agreement with biological/chemical data. Furthermore, there is also a very good agreement with FTIR data reported in literature.
ISSN:0003-004X
1945-3027
DOI:10.2138/am.2014.4542