Rietveld structure refinement of precipitated carbonate apatite using neutron diffraction data

The effect of type-B carbonate content on the elasticity of fluorapatite

“…Both spectra of the CFAP samples exhibit the typical absorption bands of CO groups in the spectral region 1400-1600 cm . The asymmetric-stretching bands of CO (ν ) are observed at 1455 and 1430 cm , and are characteristic of a type-B substitution, whereas the out-of-plane bending mode of CO (ν ) is observed at 865 cm , in agreement with those reported in the literature (Elliott 1994;Wilson et al 2004;Fleet 2009;Yi et al 2013). The carbonate-band intensities (absorbance) in the FRA spectrum (Fig.…”

“…The higher content of carbonate in FRA with respect to FOW is consistent with the observed a unit-cell parameter reduction from 9.3527(1) to 9.3330(1) Å and the significant increase of the c parameter from 6.8752(1) to 6.8984(1) Å (Table 3). The results of the structure refinement at room temperature (Table 4) show that, within FRA CFAP, the B carbonate ion is located close to the substituted phosphate group and the C atoms occupies a position (occupancy = 0.11) similar to the one observed by Wilson et al (2004) in a sodium carbonate-bearing apatite and by Yi et al (2013) in CFAP. In FOW CFAP, it was not possible to determine the position of the C atoms because of the low carbonate content.…”

“…Several studies (Elliott 1994;Wilson et al 1999Wilson et al , 2004Elliott et al 2002) have noted that the occupancy of the phosphorus position gives the most reliable estimate of the extent of substitution by type-B carbonate. The occupancies of P in FOW and FRA CFAP (Table 4) become significantly less than unity, and these data are consistent with a substitution of the (PO ) phosphate group by the (CO ) carbonate ion.…”

“…Whereas the structural details of FAP, CAP, and HAP are generally well-established, those of "carbonated" apatite are not yet very clear (Liu et al 2011;Yi et al 2013). Due to the importance of carbonate-bearing HAP in biomineralization (Elliott 2002), the incorporation of carbonate into apatite and its resulting physicalchemical changes have been investigated extensively and yet are still not well understood (McClellan 1980;Perdikatsis 1991;Elliott 1994;Regnier et al 1994;Nathan 1996;Wilson et al 1999Wilson et al , 2004Comodi and Liu 2000;Leventouri et al 2000;Ivanova et al 2001;Elliott et al 2002;Pan and Fleet 2002;, 2008aYi et al 2013). Incorporation of carbonate into the apatite structure can occur by substitution for both channel anion (type-A) and phosphate ion (type-B), as first suggested by McConnell (1938 1990) have shown a correlation between increased carbonate and decreased phosphate, with different effects on the unit-cell parameters (Knudsen and Gunter 2002).…”

Diffraction techniques and vibrational spectroscopy opportunities to characterise bones

“…Thus, in some case, it is more appropriate to select neutron scattering than X-ray scattering [46]. For example, in order to explain the higher bioactivity of the silicon-substituted hydroxyapatite (SiHA), Arcos et al [47,48] have considered neutron diffraction.…”