The Microscopic Structure Of The Bi-te-based Materials With Energy Band Theory

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 and Bi2Te3, Bi2Te2Se, Bi2Se2Te, Bi2Se3 are indirect-gap semiconductors. The density of states near Fermi level mainly consists of p orbitals for 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 increment of the Se mol ratio in the systems, the covalence bond component of Te(1)-Bi,Se(2)-Bi,Se(1)-Bi is gradually enhanced. Moreover, the equilibrium geometries and stabilities of BinTem(n+m=3,5) clusters have been systematically investigated by using the density-functional theory at B3LYP/LANL2DZ level. The calculated results indicate that the order of the stability of clusters is:Bi4Te>Bi2Te3> Bi3Te2>BiTe4, and the order of the chemical reactivity of the series is:Bi2Te3> Bi4Te>Bi3Te2>BiTe4. The structure of Bi2Te3 cluster is consist of layers which is good agreenment with that of the Bi2Te3 crystal.