Titanium dioxide is well known as a semiconductor material, which attracts a great deal of attention for promising applications in many fields due to its outstanding physical and chemical properties. To investigate the structural, elastic, mechanical, electronic and optical properties of various TiO 2 phases systematically, we present the ultrasoft pseudopotential planewave method within local density approximation and generalized gradient approximation, as well as the normconserving pseudopotential within hybrid functional B3LYP by first-principles calculations on fluorite, pyrite, rutile, anatase, hollandite, brookite, columbite, cotunnite, bronze and baddeleyite TiO 2 phases. The structural parameters of ten phases are calculated, which are shown to be consistent with previous theoretical and experimental data. We obtain the elastic constants of ten phases and then estimate the bulk, shear and Young's moduli, Poisson's coefficient and Lamé's constants using the Voigt-Reuss-Hill approximation. The energy band structures, density of states and charge populations of ten phases were obtained and indicated there is covalency in TiO 2 . Moreover, the complex dielectric function, refractive index and extinction coefficient of the ten phases were calculated; this data can aid future experimental research.

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Qi-Jun(刘其军) a) † , Zhang Ning-Chao(张宁超) a) , Liu Fu-Sheng(刘福生) a) , and Liu Zheng-Tang(刘正堂) b) a) Bond and Band Engineering Group,

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Structural, elastic, mechanical, electronic properties, and dispersion of optical functions of hexagonal ZnTiO3 have been investigated from first‐principles within density‐functional theory (DFT) using the norm‐conserving pseudopotentials method, within the generalized gradient approximation (GGA) to the exchange‐correlation functional. The calculated structural parameters agree with the available experimental and theoretical results. The elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and Lamé's constants as well as mechanical stability have been studied, indicating that hexagonal ZnTiO3 is mechanically stable, anisotropic, and ductile. The electronic structure and chemical bonding of hexagonal ZnTiO3 have been analyzed according to the calculated energy band structure, density of states (DOS), and charge populations. Dispersion of optical functions is shown and analyzed, including the complex dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient, loss function, and optical conductivity.