Energy minimization methods were used to simulate the migration of Zr, Si and O vacancies in zircon. Two sets of interatomic potentials were used for comparison, but only one used O-Si-O 3-body terms for SiO4. The results for Si were inconclusive, but were consistent with maintaining the integrity of the SiO4 molecular units. Both the Zr and O vacancies could migrate on 3-dimensional sub-lattice networks, and reflecting an experimentally observed diffusional isotropy. The predicted Zr-vacancy migration energy of 1.16 to 1.38eV was in good agreement with experiment; if supplemented by Zr-vacancy formation via Schottky or Frenkel defects (6.21 to 12.28eV/defect). The O-vacancy migration energies were predicted to be between 0.99 and 1.16eV. This was lower than the experimental value of 4.64eV which was measured in natural zircons, but may have included significant contributions from vacancy formation mechanisms (3.31 to 6.52eV/defect).

Native Vacancy Migration in Zircon. R.E.Williford, W.J.Weber, R.Devanathan, A.N.Cormack: Journal of Nuclear Materials, 1999, 273[2], 164-70