Magnetism of Titanium-Defected Undoped Rutile TiO2: First-Principles Calculations
The physicochemical properties of TiO2 are largely depending on the defects. Here, using first-principles calculations, we report a systematic investigation of the magnetic properties of Ti-defected rutile TiO2 systems. Our calculation results show that the VTi concentration can greatly affect the magnetism size, and the magnetism weakens with the VTi concentration decreasing. Studies on phonon dispersion curves show that systems with lower VTi concentrations of 8.33% and 6.25% are kinetically stable. Further detailed calculations on Ti11O24 system indicate that the magnetism mainly originates from four of the six nearest-neighbor O atoms of the Ti vacancy, but much less from the other two. The magnetic ground states are discussed, results showing that, for Ti11O24 system the FM state of the four nearest-neighbor O atoms of the Ti vacancy is the magnetic ground state, and for Ti22O48 system the FM state of the two vacancies is the magnetic ground state. In addition, calculations also indicate that the magnetic properties of Ti-defected TiO2 can be tuned via strain engineering. In general, this metal-defected TiO2 represents a new kind of semiconductor. Researches on magnetic properties in this paper can enrich the theoretical knowledges in this area and provide more potentials for TiO2-based materials.