Oxygen-vacancy driven electron localization and itinerancy in rutile-based TiO2

Article

关键词: METAL-INSULATOR-TRANSITION;    INITIO MOLECULAR-DYNAMICS;    TOTAL-ENERGY CALCULATIONS;    CRYSTAL-STRUCTURE;    ANATASE;    GAMMA-TI3O5;    BEHAVIOR;    OXIDES;    SPIN;    VO2;   

DOI  :  10.1103/PhysRevB.95.195159

来源: SCIE

【 摘 要 】

Oxygen-deficient TiO2 in the rutile structure as well as the Ti3O5 Magneli phase is investigated within the charge self-consistent combination of density functional theory with dynamical mean-field theory. It is shown that an isolated oxygen vacancy (V-O) in titanium dioxide is not sufficient to metallize the system at low temperatures. In a semiconducting phase, an in-gap state is identified at epsilon(IG) similar to -0.75 eV in excellent agreement with experimental data. Bandlike impurity levels, resulting from a threefold V-O-Ti coordination as well as entangled (t(2g), e(g)) states, become localized due to site-dependent electronic correlations. Charge localization and strong orbital polarization occur in the V-O-near Ti ions, the details of which can be modified by a variation of the correlated subspace. At higher oxygen vacancy concentration, a correlated metal is stabilized in the Magneli phase. A V-O-defect rutile structure of identical stoichiometry shows key differences in the orbital-resolved character and the spectral properties. Charge disproportionation is vital in the oxygen-deficient compounds, but obvious metal-insulator transitions driven or sustained by charge order are not identified.

【 授权许可】

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