Abstract
The atomic arrangements of eight synthetic samples along the fluorapatite-hydroxylapatite join were examined using X‑ray crystallographic techniques; the results of those refinements demonstrate that the incorporation of both F and OH in the apatite anion column, mimicking the human apatite system as modified by fluoridation, is complex. The compositions of the anion columns in the phases ranged from [F0.40(OH)0.60] to [F0.67(OH)0.33], and the high-precision structure refinements yielded R1 values from 0.0116 to 0.0140. The apatite structure responds to the variable content of the anion columns. Counterintuitively, the OH groups in the anion column move monotonically closer to the mirror planes at z = 1⁄4, 3⁄4 with increasing F content, despite the decreasing size of the triangle of Ca2 atoms to which the column anions bond and the increasing overbonding of the hydroxyl oxygen. In the structure the F atoms are underbonded and have zero degrees of positional freedom in the (0,0,1⁄4) special position to relieve that underbonding; the bonding deficiency of the anion column is relieved by the overbonding of the O(H) atom in the anion column, overbonding that increases with increasing content of underbonded F in the anion column. Together the underbonded F and the overbonded OH meet the formal bond valence (1.0 v.u.) required by the anion column occupants. The changes in bonding from the individual anion column occupants to the surrounding Ca2 atoms with composition induce bond length changes principally in the irregular Ca2 polyhedron and also affect the a lattice parameter in the apatites. The bond valence values imparted on the F, OH column anions, when extrapolated to end-member compositions, suggest that different column anion arrangements may exist near the F and OH end-member compositions, as is also seen along the apatite Cl-OH join. These values have implications for the incorporation of fluoride in human teeth during the fluoridation process.
Acknowledgments
Support for this work was provided by the National Science Foundation through grants NSF-MRI 1039436 and EAR-1249459 to J.M.H. and EAR-0952298 to J.R. The manuscript was improved by reviews by Francis McCubbin and Adrian Fiege. The authors greatly appreciate the editorial handling by Assistant Editor Aaron Celestian. Max Wilke and Sarah Cichy are thanked for running the F-OH apatite synthesis experiments in the internally heated gas pressure vessel.
References cited
Akella, J., Vaidya, S.N., and Kennedy, G.C. (1969) Melting of sodium chloride at pressures to 65 kbar. Physical Review, 185(3), 1135–1140.10.1103/PhysRev.185.1135Search in Google Scholar
Brese, N.E., and O’Keeffe, M. (1991) Bond-valence parameters for solids. Acta Crystallographica, B47, 192–197.10.1107/S0108768190011041Search in Google Scholar
Chew, D.M., and Spikings, R.A. (2015) Geochronology and thermochronology using apatite: time and temperature, lower crust to surface. Elements, 11, 189–194.10.2113/gselements.11.3.189Search in Google Scholar
Constantz, B.R., and Osaka, G.C. (1994) Hydroxyapatite prosthesis coatings. U.S. Patent 5,279,831 A.Search in Google Scholar
Elser, J., Metson, G., and Bennet, E. (2012) Uncertain supplies, shifting demands, and the sustainability of the human phosphorus cycle. 9th INTECOL International Wetlands Conference, Orlando, Florida.Search in Google Scholar
Etter, B., Tilley, E., Khadka, R., and Udert, K.M. (2011) Low-cost struvite production using source-separated urine in Nepal. Water Research, 45, 852–862.10.1016/j.watres.2010.10.007Search in Google Scholar PubMed
Ewing, R.C., and Wang, L. (2002) Phosphates as nuclear waste forms. Reviews in Mineralogy and Geochemistry, 48, 673–700.10.2138/rmg.2002.48.18Search in Google Scholar
Featherstone, J.D. (1999) Prevention and reversal of dental caries: role of low level fluoride. Community Dentistry and Oral Epidemiology, 27, 31–40.10.1111/j.1600-0528.1999.tb01989.xSearch in Google Scholar PubMed
Harlov, D.E. and Aranovich, L., Eds. (2018) The Role of Halogens in Terrestrial and Extraterrestrial Geochemical Processes: Surface, Crust, and Mantle, 1030 pp. Springer.10.1007/978-3-319-61667-4Search in Google Scholar
Hawthorne, F.C., and Grice, J.D. (1990) Crystal-structure analysis as a chemical analytical method: application to light elements. Canadian Mineralogist, 28, 693–702.Search in Google Scholar
Harlov, D.E., and Rakovan, J.F., Eds. (2015) Apatite: A mineral for all seasons. Elements, 11, no. 3.10.2113/gselements.11.3.171Search in Google Scholar
Hughes, J.M. (2015) The many facets of apatite. Mineralogical Society of America Presidential Address. American Mineralogist, 100, 1033–1039.10.2138/am-2015-5193Search in Google Scholar
Hughes, J.M., and Rakovan, J. (2002) The crystal structure of apatite, Ca5(PO43(F,OH,Cl). Reviews in Mineralogy and Geochemistry, 48, 1−12.10.2138/rmg.2002.48.1Search in Google Scholar
Hughes, J.M., and Rakovan, J. (2015) Structure, chemistry, and properties of apatite and apatite supergroup minerals. Elements, 11, 165–170.10.2113/gselements.11.3.165Search in Google Scholar
Hughes, J.M., Cameron, M., and Crowley, K.D. (1990) Crystal structures of natural ternary apatites: solid solution in the Ca5(PO43X (X = F, OH, Cl) system. American Mineralogist, 75, 295–304.Search in Google Scholar
Hughes, J.M., Heffernan, K.M., Goldoff, B., and Nekvasil, H. (2014a) Cl-rich fluorapatite, devoid of OH, from the Three Peaks Area, Utah: The first reported structure of natural Cl-rich fluorapatite. Canadian Mineralogist, 52, 643–652.10.3749/canmin.1400014Search in Google Scholar
Hughes, J.M., Nekvasil, H., Ustunisik, G., Lindsley, D.H., Coraor, A.E., Vaughn, J., Phillips, B., McCubbin, F.M., and Woerner, W.R. (2014b) Solid solution in the fluorapatite-chlorapatite binary system: High-precision crystal structure refinements of synthetic F-Cl apatite. American Mineralogist, 99, 369–376.10.2138/am.2014.4644Search in Google Scholar
Hughes, J.M., Harlov, D., Kelly, S.R., Rakovan, J., and Wilke, M. (2016) Solid solution in the apatite OH-Cl binary system: compositional dependence of solid solution mechanisms in calcium phosphate apatites along the Cl-OH binary. American Mineralogist, 101, 1783–1791.10.2138/am-2016-5674Search in Google Scholar
Kelly, S., Rakovan, J., and Hughes, J.M. (2017) Column anion arrangements in chemically zoned chlorapatite and fluorapatite from Kurokura, Japan. American Mineralogist, 102, 720–727.10.2138/am-2017-5825Search in Google Scholar
Kerssens, M.M., Matousek, P., Rogers, K., and Stone, N. (2010) Towards a safe non-invasive method for evaluating the carbonate substitution levels of hydroxyapatite (HAP) in micro-calcifications found in breast tissue. Analyst, 135(12), 3156–3161.10.1039/c0an00565gSearch in Google Scholar PubMed
Pasteris, J.D., Yoder, C.H., and Wopenka, B. (2014) Molecular water in nominally unhydrated hydroxylapatite: The key to a better understanding of bone material. American Mineralogist, 99, 16–27.10.2138/am.2014.4627Search in Google Scholar
Payne, S.A., DeLoach, L.S., Smith, L.K., Kway, W.L., Tassano, J.B., Krupke, W.F., Chai, B.H.T., and Loutts, G. (1994) Ytterbium-doped apatite-structure crystals: A new class of laser materials. Journal of Applied Physics, 76, 497–503.10.1063/1.357101Search in Google Scholar
Piccoli, P.M., and Candela, P.A. (2002) Apatite in igneous systems. Reviews in Mineralogy and Geochemistry, 48, 255–292.10.1515/9781501509636-009Search in Google Scholar
Putnis, A. (2009) Mineral replacement reactions. In E.H. Oelkers and J. Schott, Eds., Thermodynamics and Kinetics of Water-Rock Interaction. Reviews in Mineralogy and Geochemistry, 70, p. 87–124. Mineralogical Society of America, Chantilly, Virginia.10.1515/9781501508462-005Search in Google Scholar
Rakovan, J.F., and Pasteris, J.D. (2015) A technological gem: materials, medical, and environmental mineralogy of apatite. Elements, 11, 195–200.10.2113/gselements.11.3.195Search in Google Scholar
Schettler, G., Gottschalk, M., and Harlov, D.E. (2011) A new semi-micro wet chemical method for apatite analysis and its application to the crystal chemistry of fluorapatite-chlorapatite solid solutions. American Mineralogist, 96, 138–152.10.2138/am.2011.3509Search in Google Scholar
Sheldrick, G.M. (2008) A short history of SHELX. Acta Crystallographica, A64, 112–122.10.1107/S0108767307043930Search in Google Scholar PubMed
Stock, M.J., Humphreys, M.C.S., Smith, V.C., Johnson, R.D., Pyle, D.M., and EIMF (2015) New constraints on electron beam induced halogen migration in apatite. American Mineralogist, 100, 281–293.10.2138/am-2015-4949Search in Google Scholar
Stormer, J.C., Pierson, M.L., and Tacker, R.C. (1993) Variation of F and Cl X‑ray intensity due to anisotropic diffusion in apatite during electron microprobe analysis. American Mineralogist, 78, 641–648.Search in Google Scholar
Wright, J., and Conca, J. (2002) Remediation of groundwater and soil contaminated with metals and radionuclides using apatite II, a biogenic apatite mineral. In Extended Abstracts of the 2002 American Chemical Society Meeting, August 18–22, American Chemical Society, Columbus, Ohio.Search in Google Scholar
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