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Issue 4, 2008
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Probing the surface structure of hydroxyapatite using NMR spectroscopy and first principles calculations

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Abstract

The surface characteristics of hydroxyapatite (HA) are probed using a combination of NMR spectroscopy and first principles calculations. The NMR spectrum is taken from a bone sample and the first principles calculations are performed using a plane-wave density functional approach within the pseudopotential approximation. The computational work focuses on the (100) and (200) surfaces, which exhibit a representative range of phosphate, hydroxyl and cation bonding geometries. The shielding tensors for the 31P, 1H and 17O nuclei are calculated from the relaxed surface structures using an extension of the projector augmented-wave method. The calculated 31P chemical shifts for the surface slab are found to be significantly different from the bulk crystal and are consistent with the NMR data from bone and also synthetically prepared nanocrystalline samples of HA. Rotational relaxations of the surface phosphate ions and the sub-surface displacement of other nearby ions are identified as causing the main differences. The investigation points to further calculations of other crystallographic surfaces and highlights the potential of using NMR with ab initio modelling to fully describe the surface structure and chemistry of HA, which is essential for understanding its reactivity with the surrounding organic matrix.

Graphical abstract: Probing the surface structure of hydroxyapatite using NMR spectroscopy and first principles calculations

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Publication details

The article was received on 20 Sep 2007, accepted on 05 Nov 2007 and first published on 26 Nov 2007


Article type: Paper
DOI: 10.1039/B714512H
Citation: Phys. Chem. Chem. Phys., 2008,10, 600-606
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    Probing the surface structure of hydroxyapatite using NMR spectroscopy and first principles calculations

    H. Chappell, M. Duer, N. Groom, C. Pickard and P. Bristowe, Phys. Chem. Chem. Phys., 2008, 10, 600
    DOI: 10.1039/B714512H

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