| In this work,the electronic and optical properties ofⅡ-Ⅵchalcogenide compounds and their alloys were theoretically studied by means of first principles calculations in the framework of density functional theory(DFT) and based on the full-potential linearized augmented plane wave plus local orbitals(FP-LAPW+LO) method.The content is summarily described as follows.The electronic and optical properties of barium chalcogenide compounds BaX(X=S, Se and Te) in NaCl crystal structure have been studied using FP-LAPW+LO method.The band structures show that all of the three compounds have an indirect(Γ→Χ) band gap, confirming the experimental results.Our calculated band gaps are in fair agreement with experiments and much better than other theoretical studies.The real and imaginary parts of the dielectric function and reflectivity are calculated.The calculated results show good agreement with the available experimental results,particularly in the low energy region of the spectra.The effect of the spin-orbit coupling(SOC) on the optical properties is also investigated and found to be significant,especially in the high-energy regions.The electronic properties of the BaSxSe1-x alloys are investigated through FP-LAPW method.Our results show that the lattice constant scales linearly with the composition obeying Vegard's law.A linear relationship is observed between theoretical band gap and 1 /α2(where a is lattice constant).A series of first principles calculations have been carried out to study the optical properties of ZnSxSe1-x alloys for the first time in theory.The electronic structure,density of state(DOS) and band structure were calculated.We also have interpreted the origin of the spectral peaks on the basis of the electronic band structures.The change regularity was clarified.We have investigated the structural,electronic and optical properties of SrSe compound under pressure for both B1(rocksalt) and B2(cesium chloride ) structure.The pressure dependence of the band gaps of SrSe are found to be linear with pressure for both phases. |
