Structure of calcium metaphosphate Ca(PO3)2

Rothammel, W.; Burzlaff, H.; Specht, R. C.

doi:10.1107/s0108270188012922

Cited by 24 publications

(22 citation statements)

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“…The total Ca-O coordination number of 5.01 for the glass is relatively small compared to the average value of 7.5 for crystalline -Ca(PO 3 ) 2 [87], but the crystal has a much longer average Ca-O bond length of 2.47 Å compared to the average value of 2.38 Å for the fit reported in Table 6, and so the result may be reasonable. In a combined neutron and X-ray diffraction study of calcium metaphosphate glass, Wetherall et al [44] have found a Ca-O coordination of 5.2 at a distance of 2.35 Å, similar to our result, and also additional coordination of 1.7 at a distance of 2.86 Å, beyond the range that we have addressed.…”

Section: Modifier Coordination In Binary Metaphosphatesmentioning

confidence: 80%

Structural and physico-chemical analysis of calcium/strontium substituted, near-invert phosphate based glasses for biomedical applications

Patel¹,

Moss²,

Hossain³

et al. 2017

Acta Biomaterialia

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Neutron diffraction, 23 Na and 31 P NMR and FTIR spectroscopy have been used to investigate the structural effects of substituting CaO with SrO in a 40P 2 O 5 ·(16-x)CaO·20Na 2 O·24MgO·xSrO glass, where x is 0, 4, 8, 12 and 16 mol%. The 31 P solid-state NMR results showed similar amounts of Q 1 and Q 2 units for all of the multicomponent glasses investigated, showing that the substitution of Sr for Ca has no effect on the phosphate network. The M-O coordinations (M= Mg, Ca, Sr, Na) were determined for binary alkali and alkaline earth metaphosphates using neutron diffraction and broad asymmetric distributions of bond length were observed, with coordination numbers that were smaller and bond lengths that were shorter than in corresponding crystals. The Mg-O coordination number was determined most reliably as 5.0(2). The neutron diffraction results for the multicomponent glasses are consistent with a structural model in which the coordination of Ca, Sr and Na is the same as in the binary metaphosphate glass, whereas there is a definite shift of Mg-O bonds to longer distance. There is also a small but consistent increase in the Mg-O coordination number and the width of the distribution of Mg-O bond lengths, as Sr substitutes for Ca. Functional properties, including glass transition temperatures, thermal processing windows, dissolution rates and ion release profiles were also investigated. Dissolution studies showed a decrease in dissolution rate with initial addition of 4 mol% SrO, but further addition of SrO showed little change. The ion release profiles followed a similar trend to the dissolution rates observed. The limited changes in structure and dissolution rates observed for substitution of Ca with Sr in these fixed 40 mol% P 2 O 5 glasses were attributed to their similarities in terms of ionic size and charge.

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Section: Modifier Coordination In Binary Metaphosphatesmentioning

confidence: 80%

Structural and physico-chemical analysis of calcium/strontium substituted, near-invert phosphate based glasses for biomedical applications

Patel¹,

Moss²,

Hossain³

et al. 2017

Acta Biomaterialia

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“…The input for the Ca containing systems were the structures Ca 3 P 2 O 8 of Roux et al [31], Ca 2 P 2 O 7 of Boudin et al [32], and the CaP 2 O 6 structrures of Rothammel et al [33] as well as that of Schneider et al [34]. In order to avoid dependencies of our results on pseudopotential forms PopleÕs standard STO-6G basis functions were used for all the electrons in the CRYSTAL program.…”

Section: Computational Detailsmentioning

confidence: 99%

Preparation and structural study of binary phosphate glasses with high calcium and/or magnesium content

Karakassides

Saranti

Koutselas

2004

Journal of Non-Crystalline Solids

209

125

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“…The crystalline structure is described as an infinite periodic system using periodic boundary conditions. The NMR calculations were performed for the experimental geometries determined by neutron or X-ray diffraction for the various calcium phosphates: brushite, CaHPO 4 $2H 2 O [28]; MCPM, [30]; g-Ca(PO 3 ) 2 [31]; Ca 4 P 2 O 9 [32]. In the case of Ca 4 P 2 O 9 , a significant better agreement is obtained between experimental and calculated 31 P parameters by taking into account a geometry optimization (starting from the experimental geometry and allowing the positions of the atoms to relax using DFT calculations).…”

Section: Calcmentioning

confidence: 99%

Calcium phosphates: First-principles calculations vs. solid-state NMR experiments

Pourpoint¹,

Gervais²,

Bonhomme-Coury³

et al. 2007

Comptes Rendus. Chimie

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Structure of calcium metaphosphate Ca(PO3)2

Cited by 24 publications

References 1 publication

Structural and physico-chemical analysis of calcium/strontium substituted, near-invert phosphate based glasses for biomedical applications

Structural and physico-chemical analysis of calcium/strontium substituted, near-invert phosphate based glasses for biomedical applications

Preparation and structural study of binary phosphate glasses with high calcium and/or magnesium content

Calcium phosphates: First-principles calculations vs. solid-state NMR experiments

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