Aluminum diffusion and Al-vacancy association in periclase

James A. Van Orman, Chen Li, Katherine L. Crispin

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

Trivalent cations in periclase are attracted to cation vacancies and these defects tend to associate on adjacent sites to form mobile pairs. A theory has been developed to describe the concentration-dependent diffusion of Al in the presence of Al-vacancy pairs, and has been applied to experiments conducted at 1577-2273 K and 1 atm to 25 GPa. In all but one experiment, the Gibbs free energy of binding, inferred from the diffusion profiles, is between -44 and -60 kJ/mol, with an average value of -50 kJ/mol. The absolute value of the entropy of binding is constrained to be less than 50 J mol-1 K-1, and the volume of binding is constrained to be between -1.8 and 0 cm3/mol. The diffusion coefficient of the Al-vacancy pair can be described by the equation D2 = D2,0 exp(-(E + PV)/RT), with E = 213 ± 32 kJ/mol, V = 3.22 ± 0.25 cm3/mol, and log10D2,0 = -6.17 ± 0.99 (in m2/s; all uncertainties 2σ). Calculations are presented for the diffusion of Al and Mg as functions of Al concentration, temperature and pressure.

Original languageEnglish (US)
Pages (from-to)34-42
Number of pages9
JournalPhysics of the Earth and Planetary Interiors
Volume172
Issue number1-2
DOIs
StatePublished - Jan 1 2009

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Geophysics
  • Physics and Astronomy (miscellaneous)
  • Space and Planetary Science

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