Geometrical parameterization of the crystal chemistry of P63/m apatites: comparison with experimental data and ab initio results

Download
  1. (PDF, 918 KB)
  2. (PDF, 1 MB)
  3. Get@NRC: Geometrical parameterization of the crystal chemistry of P63/m apatites: comparison with experimental data and ab initio results (Opens in a new window)
DOIResolve DOI: http://doi.org/10.1107/S0108768105031125
AuthorSearch for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for:
TypeArticle
Journal titleActa Crystallographica Section B: Structural Science, Crystal Engineering and Materials
ISSN2052-5192
2052-5206
Volume61
Issue6
Pages635655; # of pages: 21
Subjectapatite; crystal chemistry; geometric crystal-chemical modelling; ab initio calculations; crystal structure analysis
AbstractExperimental structure refinements and ab initio simulation results for 18 published, fully ordered P63/m (A^{\rm I}_4)(A^{\rm II}_6)(BO4)6X2 apatite end-member compositions have been analyzed in terms of a geometric crystal-chemical model that allows the prediction of unit-cell parameters (a and c) and all atom coordinates. To an accuracy of ± 0.025 Å, the magnitude of c was reproduced from crystal-chemical parameters characterizing chains of ...-AII-O3-B-O3-AII-... atoms, whereas that of a was determined from those describing (AIO6)-(BO4) polyhedral arrangements. The c/a ratio could be predicted to ±0.2% using multi-variable functions based on geometric crystal-chemical model predictions, but could not be ascribed to the adjustment of a single crystal-chemical parameter. The correlations observed between algebraically independent crystal-chemical parameters representing the main observed polyhedral distortions reveal them as the minimum-energy solution to accommodate misfit components within this flexible structure type. For materials with given composition, good agreement (within ± 0.5-2.0%) of ab initio crystal-chemical parameters was observed with only those from single-crystal refinements with R [less-than or equal to] 4.0%. Agreement with single-crystal work with R > 4.0% was not as good, while the scatter with those from Rietveld refinements was considerable. Accordingly, ab initio cell data, atomic coordinates and crystal-chemical parameters were reported here for the following compositions awaiting experimental work: (Zn,Hg)10(PO4)6(Cl,F)2, (Ca,Cd)10(VO4)6Cl2 and (Ca,Pb,Cd)10(CrO4)6Cl2.
Publication date
PublisherInternational Union of Crystallography
Other version
LanguageEnglish
AffiliationNational Research Council Canada; NRC Institute for Chemical Process and Environmental Technology
Peer reviewedNo
NRC numberNRCC 47848
NPARC number8925995
Export citationExport as RIS
Report a correctionReport a correction
Record identifier5698665f-031e-49ab-9278-b80109611a30
Record created2009-04-23
Record modified2017-08-17
Bookmark and share
  • Share this page with Facebook (Opens in a new window)
  • Share this page with Twitter (Opens in a new window)
  • Share this page with Google+ (Opens in a new window)
  • Share this page with Delicious (Opens in a new window)