Minerals and Materials Science and Technology, Mawson Institute, Division of IEEE, University of South Australia, Mawson Lakes Campus, South Australia 5095, Australia.
J Phys Condens Matter. 2011 Jan 19;23(2):025901. doi: 10.1088/0953-8984/23/2/025901. Epub 2010 Dec 16.
We present an analysis of the dielectric properties of the three polymorphs of TiO₂ (rutile, anatase and brookite phases), using ab initio time-dependent density functional perturbation theory based on the Vignale-Kohn functional. We implement this functional, which incorporates many-body effects, using the periodic program BAND. The improved result for the density of states spectra for brookite is suggestive of increased titanium ion Jahn-Teller effects for this phase. The imaginary and real components of the frequency-dependent dielectric functions show notable dielectric anisotropies, with implications for excitonic interactions, for all three common phases of TiO₂. Comparison of the electron energy-loss spectrum for undoped and doped rutile and anatase reveals the critical role of collective charge excitations in photocatalytic mechanisms. The correlation between plasmon peaks present at lower energies and decreased photocatalytic activity due to substitutional aluminum doping in combination with oxygen vacancies in rutile and anatase is highlighted. Moreover, there is clear correlation between dielectric properties and the microstructure of the TiO₂ polymorphs as suggested via the framework of the Born effective charge and Hirshfeld charge distribution schemes.
我们使用基于 Vignale-Kohn 泛函的第一性原理含时密度泛函微扰理论，对 TiO₂ 的三种多晶型（金红石、锐钛矿和板钛矿相）的介电性质进行了分析。我们使用周期性程序 BAND 实现了这个包含多体效应的泛函。板钛矿的态密度谱的改进结果表明，该相的钛离子 Jahn-Teller 效应增强。对于 TiO₂ 的所有三种常见相，频率相关介电函数的虚部和实部都表现出显著的介电各向异性，这对激子相互作用有影响。与掺杂和未掺杂的金红石和锐钛矿的电子能量损失谱的比较揭示了集体电荷激发在光催化机制中的关键作用。由于在金红石和锐钛矿中存在替代铝掺杂和氧空位，导致较低能量的等离子体峰与光催化活性降低之间存在相关性，这一点得到了强调。此外，介电性质与 TiO₂ 多晶型的微观结构之间存在明显的相关性，这一点可以通过 Born 有效电荷和 Hirshfeld 电荷分布方案的框架来解释。
