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Initial stages of hydration and Zn substitution/occupation on hydroxyapatite (0 0 0 1) surfaces

Paper ID Volume ID Publish Year Pages File Format Full-Text
10265 676 2008 9 PDF Available
Title
Initial stages of hydration and Zn substitution/occupation on hydroxyapatite (0 0 0 1) surfaces
Abstract

The initial stages of the hydration process have been simulated on a single-Ca(I) terminated hydroxyapatite (0 0 0 1) surface in step-by-step fashion using periodic slab density functional theory (DFT). Adsorption configurations and energetic properties have been described at different H2O coverage. At low H2O coverage, oxygen prefers to form CaO bonds with surface Ca cations, but as coverage increases, H2O tends to loosely float on the already-formed water layer. The height of the first layer H2O relative to the surface is found to be 1.6 Å. The hydration process does not cause the decomposition of surface phosphate groups and hydroxyl channel, but does affect the energetics of subsequent Zn substitution and occupation on Ca(I) and Ca(II) sites. The Ca(II) vacancy site is found to be energetically more favorable for occupation due to less spatial constraint. This suggested mechanism of preferential occupation is different from previous attempts to explain the cation substitution site preference in bulk by ionic radius and electronegativity differences.

Keywords
DFT; Hydroxyapatite; Hydration; Ion exchange; Preferential site occupancy
First Page Preview
Initial stages of hydration and Zn substitution/occupation on hydroxyapatite (0 0 0 1) surfaces
Publisher
Database: Elsevier - ScienceDirect
Journal: Biomaterials - Volume 29, Issue 3, January 2008, Pages 257–265
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering