First Principles Calculations of Linear and Second-Order Optical Responses in Rhombohedrally Distorted Perovskite Ternary Halides, CsGeX3 (X = Cl, Br, and I)

doi:10.1143/JJAP.48.112402

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Title:	First Principles Calculations of Linear and Second-Order Optical Responses in Rhombohedrally Distorted Perovskite Ternary Halides, CsGeX3 (X = Cl, Br, and I)
Authors:	Tang, Li-Chuan;Chang, Yia-Chung;Huang, Jung-Yau;Lee, Ming-Hsien;Chang, Chen-Shiung
Contributors:	淡江大學物理學系 0021-4922;1347-4065
Date:	2009-11
Issue Date:	2011-10-24 10:49:54 (UTC+8)
Publisher:	Tokyo: Institute of Pure and Applied Physics
Abstract:	Systematic studies based on first-principles calculations of second-order optical susceptibilities as well as the dielectric function of CsGeX3 (X = Cl, Br, and I; CGX) are presented. The relationship between structural properties and optoelectronic responses are examined. The structural factors Δα, and dGe, dX are proposed to describe the degree of distortion from an ideal perovskite structure. Δα and dGe increase when halide anions are changed from Cl to I; while halide anion displacement, dX, decreases. The structural distortion effect on these rhombohedral CGX crystals is analyzed by first-principles calculations. The dielectric function and the second harmonic generation (SHG) response coefficient also increase with increasing Δα and dGe. The direct band gaps (EG) of CsGeX3 all occur at the R-point, ΔER. The experimental band gaps of CGX crystals become smaller, i.e., ECGCG (=3.67 eV) >ECGBG (=2.32 eV) >ECGIG (=1.53 eV), as Δα and dGe increase, i.e., dCGCGe<dCGBGe<dCGIGe. Partial density of states (PDOS) analysis revealed that the valence band maximum (VBM) and conduction band minimum (CBM) are mainly contributed by the p-orbitals of germanium. The calculated magnitudes of χ(2)ijk are close to some reported experimental values near the band gap.
Relation:	Japanese Journal of Applied Physics 48, 112402(9pages)
DOI:	10.1143/JJAP.48.112402
Appears in Collections:	[Graduate Institute & Department of Physics] Journal Article

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