The effect of chemical potential on the thermodynamic stability of carbonate ions in hydroxyapatite

Acta Biomater. 2014 Aug;10(8):3716-22. doi: 10.1016/j.actbio.2014.05.007. Epub 2014 May 10.

Abstract

First-principles calculations were performed for CO3(2-) ions in hydroxyapatite in order to investigate the atomic structures and thermodynamic stability of CO3(2-) and its related defects. Two different chemical equilibrium conditions in high-temperature and aqueous-solution environments were considered, and atomic and ionic chemical potentials for the individual chemical equilibrium conditions were evaluated to calculate defect formation energies. It was found that A-type CO3(2-) (substituting OH(-)) is energetically more favorable than B-type CO3(2-) (substituting PO4(3-)) in the high-temperature environment, whereas B-type is preferred to A-type in the aqueous solution environment. This result successfully reproduces experimentally observed trends. In the formation of A-type and B-type CO3(2-), OH(-) vacancies or protons (interstitial or substitutional) act as charge-compensating defects.

Keywords: Carbonate ion; Defect formation energy; First-principles calculation; Hydroxyapatite; Thermodynamic stability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apatites / chemistry*
  • Biocompatible Materials / chemistry*
  • Carbonates / chemistry*
  • Computer Simulation
  • Drug Stability
  • Durapatite / chemistry*
  • Materials Testing
  • Models, Chemical*
  • Models, Molecular*
  • Thermodynamics

Substances

  • Apatites
  • Biocompatible Materials
  • Carbonates
  • carboapatite
  • Durapatite