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

Xiaoyan Ma, Donald E. Ellis*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

62 Scopus citations


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 Ca{single bond}O 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.

Original languageEnglish (US)
Pages (from-to)257-265
Number of pages9
Issue number3
StatePublished - Jan 2008


  • DFT
  • Hydration
  • Hydroxyapatite
  • Ion exchange
  • Preferential site occupancy

ASJC Scopus subject areas

  • Bioengineering
  • Ceramics and Composites
  • Biophysics
  • Biomaterials
  • Mechanics of Materials


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