Bi2Te3-xSex(X≤3)同晶化合物电子结构的第一性原理研究

摘要

Based on density functional theory with spin-orbit corrections included, the electronic structures of diadochic compounds Bi2Te3-xSex( x ≤ 3 ) have been calculated by first-principles full-potential linearized augmented plane-wave method. The calculated results indicate that spin-orbit interaction is crucial in understanding the gap structure near the Fermi energy. Bi2Te3*xSex(x≤3) are indirect-gap semiconductors, and there is a saddle point at the Г point. The density of states near Fermi level mainly consists of p orbitals of each atom. For the chemical bonding of the various layers of atoms, the covalence bond component of X(1)-Bi is stronger than that of X(2)-Bi (X = Te, Se). With the increase of the Se mol ratio in the systems, the unit cell volume is reduced, the energy of the system is increased, and the covalence bond component of Te(1)-Bi, Se(2)-Bi, Se(1)-Bi is gradually enhanced.%本文采用基于密度泛函理论的第一性原理全势能线性缀加平面波方法(FLAPW),分析了Bi2Te3-xSex体系中各原子自旋轨道耦合(SOI)的P1/2修正对体系性质的影响,并对Bi2Te3-xSex(x≤3)同晶化合物的电子特性进行系统的理论研究,首次计算出Bi2Se2Te的电子特性.计算结果表明:对于Bi2Te3-xSex体系中的Te原子和Bi原子考虑SOI的P1/2修正,对体系费米能级附近能带结构的计算分析尤为重要,而对于Bi2Se2Te和Bi2Te2Se中的Se原子是否考虑SOI的Pi/2修正对费米能级附近的能带结构无显著影响;Bi2Te3-xSex(x≤3)均为间接带隙窄带半导体,体系在费米能级附近Γ点的能带趋势相近,强的杂化压低了价带的最高峰,使得两个边锋提高,在Γ点形成马鞍点;体系费米能级附近的电子态密度主要来源于各原子p态电子贡献;层间原子成键,X(1)-Bi键比X(2)-Bi键(X=Te,Se)的共价键成分较强;随着体系中Se原子摩尔比的增加,晶胞的体积减小,体系的能量增加,Te(1)-Bi键、Se(2)-Bi键、Se(1)-Bi键的共价键成分逐渐增强.