Thermodynamics of oxygen defective Magneli Phases in Rutile: A First Principles Study

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We used Ab initio thermodynamics to calculate the formation energies, in different environmental conditions, of a number of oxygen-defective structures in rutile. In addition to the TinO(2n−1) (n=3,4,5) Magnéli phases, we also considered the two fundamental points defects, Ti interstitials and neutral oxygen vacancies. We compared the predicted phase stability diagram with available experimental data, and and found reasonable agreement between the calculated phase boundaries and those observed. We used these results to discuss a mechanism that has been proposed as an explanation for the formation of the crystallographic shear planes in rutile.