The Application Of Density Functional Theory In Crystal Doping

The alkaline earth metal Ca₂Ge is a new type of environmentally friendly semiconductor material,and had been attracted for its potential use?new environmentally friendly electronic products?.As the study of Ca₂Ge started recently,the relevant literature reports and data very few.The purpose of this study is to enhance the performance of Ca₂Ge material,to the regulation object which may better serve the relevant field.In this study,the first principle plane wave method is used,the band structure,dielectric function,absorption coefficient and magnetic properties of Ca₂Ge,Sr-doped Ca₂Ge system,Fe and Co magnetic doped Ca₂Ge system are investigated,the content as the following:?1?Based on the DFT first principle plane wave method,the geometrical structure,energy band structure,dielectric function and energy loss function of block Ca₂Ge were explored.From which we concluded that Ca₂Ge is a direct bandgap semiconductor with Eg =0.306 e V and static dielectric constant and refractive index of 21.5 and 4.6,respectively.?2?The geometrical structure,band structure,dielectric function and energy loss function of Sr doped Ca₂Ge were investigated by using the DFT first principle plane wave method.The result of the calculation: Sr doping Ca₂Ge,the Fermi surface and its vicinity of the band structure,dielectric function and energy loss function has undergone significant changes,the bandgap value increased from 0.306 e V to 0.350 e V,the reason for this change is that the 3p state of Sr is hybridized with the 3s state of the Ca atom and the 3p state of the Ge atom.The refractive index of the system was enhanced,while the reflection spectrum reduced,the electronic transition ability becomes stronger,while the optical properties were improved.?3?The formation enthalpy and the spin density of Fe-doped Ca₂Ge were calculated,comparison of the stability of Fe-doped bulk Ca₂Ge at different positions,and the reason of magnetic properties of Fe-doped block Ca₂Ge was analyzed.?4?The formation enthalpy and the spin density of Fe-doped Ca₂Ge were calculated,the stability of Co-doped Ca₂Ge in two different positions was compared,and the reason of magnetic properties of Fe-doped block Ca₂Ge was analyzed.