Molecular dynamics simulations of vacancy diffusion in chromium(III) oxide, hematite, magnetite and chromite

• Vacancy diffusion in α-Cr2O3, α-Fe2O3, Fe3O4 and FeCr2O4 was studied by direct MD simulations.
• Activation energies for migration were 0.37–0.91 eV (cations) and 0.57–1.34 eV (oxygen).
• In α-Cr2O3 and α-Fe2O3, cations were clearly more mobile than oxygen.
• In FeCr2O4, the mobility of the ions behaved as Fe2 + > O2 − > Cr3 +.
• In Fe3O4, only Fe2 + exhibited mobility that was detectable in the simulations.

Mass transport in bulk α-Cr2O3, α-Fe2O3, Fe3O4 and FeCr2O4 has been studied by means of classical molecular dynamics (MD) simulations. Point defects were assumed to be responsible for ionic diffusion. The focus of this study were vacancies both in the cation and anion lattice (Schottky defects). The Buckingham potential was used to describe the interactions between ions. Defect concentrations in the 10− 4 to 10− 3 range were studied in the temperature range 1300 K–2000 K. Diffusion coefficients were calculated from mean square displacements. Activation energies for migration were determined from Arrhenius plots.