采用基于第一性原理的赝势平面波方法,对Bi Ti O3的多种结构进行了计算.计算结果表明,C1C1结构最为稳定,对应晶格参数为a=b=5.606,c=9.954;α=β=105.1°,γ=61.2°.进一步对C1C1结构的Bi Ti O3的能带结构、电子性质和光学性质进行了研究,发现Bi Ti O3是间接带隙半导体,其费米面附近的能带主要由Ti-3d和O-2p层的电子态构成.通过介电函数、复折射率和反射率等的研究,发现Bi Ti O3的光学性质为近各向同性.
The electronic structure of pure and S-doped chalcopyrite CulnSe2 is investigated using a first-principles pseudopotential method in the generalized gradient approximation. The calculation indicates that the band gap of CulnSe2 broadens as S-doping concentration increases. We find that the decreased lattice volume due to isovalent S-doping in CulnSe2 has a significant impact on the band gap broadening phenomena. This physical insight is further discussed with the study of the electronic structure and bond length changes.
