【摘要】 为了研究锐钛矿TiO2晶体中氧空位对光学性质的影响,利用基于局域密度泛函理论框架下的广义梯度近似平面波超软赝势方法,用第一性原理对含氧空位锐钛矿TiO2晶体进行了结构优化处理,计算了完整的和含氧空位锐钛矿TiO2晶体的电子态密度、复数折射率、介电函数及吸收光谱的偏振特性。二者比较发现,引入氧空位后,锐钛矿TiO2的电子结构发生了变化,电子总态密度的费米面进入了导带,引起了莫特相变;含氧空位的锐钛矿TiO2晶体的Ti 3d态大约在-6.097 eV处出现了新的劈裂峰值。两种模型的介电函数虚部、吸收光谱以及复折射率的实部,它们的峰值位置一一对应,说明它们之间存在着内在的联系,这些都与电子态密度分布直接相关。理论分析和计算发现二者的介电函数虚部和吸收光谱峰值位置移动是弛豫效应影响的结果,同时,峰值大小变化是电子跃迁的几率来决定的。晶体的各向异性是由晶体结构的对称性决定的。更多还原

【Abstract】 The effect of oxygen vacancy in anatase TiO2 crystal on the optical property was studied by using the plane waves ultrasoft pseudopotential technique,which was based on density functional theory.The crystal structure of anatase with oxygen vacancies was optimized by using the first principle.Then electronic-state density,complex refractive index,dielectric functions and absorption spectra in pure and oxygen doped anatase TiO2 crystal were calculated.By comparing the results,we find there are some changes in electronic structure,which lead to a change of the interaction between electrons. The Fermi surface of the total density of states(TDOS) extends into the conducting band,and causes Mott phase transformation,and the Ti 3d state of the anatase crystal of TiO2 at-6.097 eV shows new split peaks.Positions of imaginary part of dielectric functions and real part of the absorption spectrum and complex refractive index are identified,showing there are inner relations between them,which are related to the state density of the electrons.By theoretical analysis and calculation,we find that the imaginary part of dielectric functions and the peak position of absorption spectrum are caused by the relaxation effect,meanwhile the height of the peaks is related to the transition probability of the electrons,and anisotropism of the crystal is determined by its symmetry structure of crystal.更多还原