尖晶石型ZnGa_2O_4光学性质的第一性原理计算

First Principles Calculations of Optical Properties of Spinel ZnGa_2O_4

首先采用基于密度泛函理论(DFT)框架下广义梯度近似平面波超软赝势法(包括PBE、PBESOL、PW91、RPBE、WC)对尖晶石型ZnGa2O4的结构进行了优化,得到和实验值最接近晶格常数a0=0.837 8 nm;然后在结构优化的基础上采用GGA-WC计算ZnGa2O4的电子结构和光学性质。结果表明,ZnGa2O4为间接带隙复合氧化物,带隙宽为2.335 eV;ZnGa2O4的静态介电常数为3.45,静态折射率为1.85,介电函数吸收边位于4.0 eV附近;ZnGa2O4的反射系数在19.3 eV附近取得最大值,吸收系数在11.0 eV^17.5eV间取值均较大,电子能量损失谱的共振峰在20.5 eV处,并与此能量时反射系数R(ω)的陡降相对应。

The generalized gradient approximation （including PBE, PW91, PBESOL, RPBE and WC） with plane wave ultrasoft pseudopotential based on the framework of density functional theory （DFT） was employed to optimize the structure of spinel ZnGa204. The calculated lattice constant of ZnGa204 is 0.837 8 nm, which is the most close to the experimental one. Next the functional of GGA-WC was used to calculate the electronic structure and optical properties of ZnGa204. The calculation results show that ZnGa204 is an indirect-band-gap semi-conductor with a wide-band gap of 2.335 eV. The static dielectric constant of ZnGa204 is 3.45, the static refractive index is 1.85, and the absorption starts at about 4.0 eV. The reflectivity of ZnGa204 reaches its highest point at 19.3 eV, the absorption is higher at from 11.0 eV to 17.5 eV, and the peak of the electron energy loss spectrum （EELS） is at 20.5 eV where there is an abrupt reduction in the the reflectivity.