摘要
通过应力调控方式,采用了GGA和LDA两种近似方法分别计算了立方相Ca2Ge在-2~4 GPa应力下的电子结构和光电特性。根据能带结构计算结果得到,在-2~4 GPa应力范围,立方相Ca2Ge均为在G高对称点的直接带隙半导体,在0 GPa下GGA和LDA计算的带隙值分别为0. 55 e V和0. 426 e V。态密度结果表明了在所有调控应力下,价带主要是由Ge的p态电子贡献,导带主要是由Ca的d态电子贡献。分析复介电函数得到,0 GPa下的静态介电常数ε1(0)取得最大值,在所有应力范围内,介电函数ε1在E=0. 7 e V附近获得最大峰值,但2 GPa和4 GPa下的介电函数最大值向低能区移动,介电函数虚部ε2峰值主要是由Ge的4p态电子向Ca的3d态跃迁所产生的。根据折射率、反射谱、吸收谱信息,-2 GPa、2 GPa和4 GPa的调控应力使立方相Ca2Ge在5. 2~6. 5 e V能量范围内呈现出了较强的金属反射特性,此时,折射率和吸收谱值为0,反射谱取得最大值1,而能量损失函数分析表明,在调控应力下,出现最大能量损失的横坐标值从10. 2 e V移动至7. 8 e V,表明了可通过施加应力方式调控光电子能量出现的最大损失。
The electronic structure and optical properties of cubic Ca2Ge have been calculated by the GGA and LDA of the pseudo-potential plane wave method,under the pressures from-2 GPa to 4 GPa. The calculated band stuctrue indicated the cubic Ca2Ge is direct band-gap semiconductor at G point with the pressure range from-2 GPa to 4 GPa,and at 0 GPa pressure,the band gaps are 0. 55 e V and 0. 426 e V when using the GGA and LDA,respectively. Analysing the density of states reveal that the valence band is mainly contributed from the Ge p-state electrons and the conduction band is mainly composed of the Ca d-state contribution. The dielectic function results show the dielectric constant of 0 GPa obtain maximum value at the point of E = 0 e V,and in other energy ranges,the dielectric constants ε1 achieve maximum peak value when the energy is near 0. 7 e V. From the dielectric function and band structure,we can also conclude the peak values of dielectric constant ε2 are mainly caused by the Ge 4 p-state electron transfer to the Ca 3 d-state electron for all pressures. Besides,according to the diagrams of refractive index,extinction coefficient,reflectivity and absorption,the phenomenon of strong metallic reflection be found in the energy range from 5. 2 e V to 6. 5 e V,under the pressures of-2 GPa,2 GPa and 4 GPa,the values of refractive index and absorption as low as 0,and the reflectivity run up to 1 in this energy range. The abscissa value of loss function with maximum energy loss move from 10. 2 e V to 7. 8 e V under the pressures effect,indicating the energy region of appearing energy loss can be changed by using pressure.
作者
吕林
杨吟野
岑伟富
姚冰
欧建开
LYU Lin;YANG Yin-ye;CEN Wei-fu;YAO Bing;OU Jian-kai(Engineering Training Center,Guizhou Minzu University,Guiyang 550025,China;Special and Key Laboratory of Guizhou Provincial Higher Education for Photoelectric Information Processing and Analysis,Guiyang 550025,China;College of Materials Engineering,Guizhou Minzu University,Guiyang 550025,China)
出处
《硅酸盐通报》
CAS
北大核心
2019年第12期3788-3795,共8页
Bulletin of the Chinese Ceramic Society
基金
贵州省教育厅青年科技人才成长项目(KY[2018]146,KY[2016]166)
贵州民族大学科研基金(2017ZD020)
