Mn掺杂浓度对Mn:MgAl_2O_4电子结构和光学性质的影响

Influence of Mn Ion Doping Concentration on Electronic Structure and Optical Properties of Mn:MgAl_2O_4

采用密度泛函理论(DFT)的平面波超软赝势(PW-USP)和广义梯度近似(GGA)对不同锰离子掺杂浓度的掺杂镁铝尖晶石晶体Mg1-xMnxAl2O4(x=0、0.125、0.5)的晶体结构、电子结构和光学性质进行了计算。解释了锰离子掺杂浓度使晶格常数变化的微观机制;分析了锰离子掺杂浓度对电子结构和光学系数的影响。结果表明,锰离子掺杂浓度的增加使掺杂晶体的带隙降低,价带变窄,杂质能级展宽。掺杂晶体的导带对掺杂浓度的变化较为敏感。锰掺杂使可见光区吸收增大,且掺杂浓度越高可见光区光学吸收越强,起吸收边越向长波方向移动,即发生红移,与实验结果一致。

The lattice and electronic structure as well as optical properties of Mg1-xMnxAl2O4 （x = 0,0. 125, 0. 5） are investigated using the pseudo-potential plane-waves approach based on density functional theory, coupled with the generalized gradient approximation. The microscopic mechanism is attempted for changes in the lattice constants due to the doping concentration of Mn ion. The effects of doping concentration on the electronic structure along with optical properties are analyzed. The results show that the band gaps decrease, the valence band becomes narrow, and the doped impurity energy level widens as the Mn ion doping concentration increases. The Mn ion doping concentration exerts a significant effect on the conductive band width. The absorption intensity in the visible range increases, and the absorptional edge shifts to the long wavelength side, （i. e. , red shift）, as the Mn ion doping concentration increases.