Computational Insight into the Effect of Monovalent Cations on the Electronic, Optical and Lattice Dynamic Properties of XInSe2 (X=Cu, Ag, Li)
Interactions between monovalent cations and anions are common in ternary AIBIIIC2VI chalcopyrite crystals, and is known to significantly influence their electronic behaviors. Density functional theory were used by CASTEP code to investigate the effect of monovalent cations on the electronic, optical and lattice dynamic properties of XInSe2 (X=Cu, Ag, Li) chalcopyrite crystals to understand the intrinsic factors determining the different physical properties. It follows that XInSe2 compounds are all direct band gap semiconductors with calculated direct band gap of 0.68, 0.88 and 2.29 eV for CuInSe2, AgInSe2 and LiInSe2 respectively. It is the hybridization of Se 4p with Cu 3d/Ag 4d states that contributes the small energy gaps of CuInSe2 and AgInSe2. In LiInSe2, Li occur as ions that provide charge balance to the InSe4 polyanion, and the hybridization between In sp and Se 4p states is mainly attribute to the larger energy gap of LiInSe2 because Li do not allow d electron interactions. The results in optical properties illustrate that for XInSe2 compounds, the larger the energy gap is, blueshifted the optical curve is and the smaller the static dielectric constant, refractive index as well as the extinction coefficient are. Additionally, the serious vibrations of the lighter Li atoms form an extra high-frequency phonon band and result in extreme high Debye temperature of LiInSe2. With the reduction of the cationic masses from Ag, Cu to Li, the corresponding phonon frequencies increase for most modes, whereas the anomalistic declines occur for A1 and A2 modes due to the high ionicity of Li-Se bonds as compared to Cu/Ag-Se bonds. The high ionicity of Li-Se bonds also gives rise to the greater LO/TO splitting of the upper phonon polar modes in LiInSe2 than in covalent CuInSe2 and AgInSe2.
Yanlu Li Weiliu Fan Honggang Sun Pan Li Xian Zhao
State Key Laboratory of Crystal Materials , Shandong University, Jinan 250100, China State Key Laboratory of Crystal Materials , Shandong University, Jinan 250100, China Department of C
国际会议
武汉
英文
471-490
2010-09-01（万方平台首次上网日期，不代表论文的发表时间）