title: Syntheses, structures, and nonlinear-optical properties of metal sulfides Ba2Ga8MS16 (M = Si, Ge).
abstract: Two new metal sulfides, Ba(2)Ga(8)MS(16) (M = Si, Ge), have been synthesized by high-temperature solid-state reactions. They are isostructural and crystallize in the noncentrosymmetric space group P6(3)mc (No. 186) with a = 10.866(5) Å, c = 11.919(8) Å, and z = 2 for Ba(2)Ga(8)SiS(16) (1) and a = 10.886(8) Å, c = 11.915(3) Å, and z = 2 for Ba(2)Ga(8)GeS(16) (2). Their three-dimensional frameworks are constructed by corner-sharing mixed (Ga/M)S(4) (M = Si, Ge) and pure GaS(4) tetrahedra, with Ba(2+) cations filling in the tunnels. Compounds 1 and 2 are transparent over 0.42-20 μm and have wide band gaps of around 3.4 and 3.0 eV, respectively. Polycrystalline 2 displays strong nonlinear second-harmonic-generation (SHG) intensities that are comparable to that of the benchmark AgGaS(2) (AGS) with phase-matching behavior at a laser irradiation of 1950 nm. Of particular interest, compound 2 also possesses a high powder laser-induced damage threshold of ∼22 times that of AGS. The alternate stacking of the mixed (Ga/M)S(4) (M = Si, Ge) tetrahedral layer with the pure GaS(4) tetrahedral layer along the c axis and the alignment of these two types of tetrahedra in the same direction may be responsible for the large SHG signals observed.
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou, Fujian 350002, P. R. China.
authors.forename: Bin-Wen
authors.initials: BW
authors.lastname: Liu
authors.forename: Hui-Yi
authors.initials: HY
authors.lastname: Zeng
authors.forename: Ming-Jian
authors.initials: MJ
authors.lastname: Zhang
authors.forename: Yu-Hang
authors.initials: YH
authors.lastname: Fan
authors.forename: Guo-Cong
authors.initials: GC
authors.lastname: Guo
authors.forename: Jin-Shun
authors.initials: JS
authors.lastname: Huang
authors.forename: Zhen-Chao
authors.initials: ZC
authors.lastname: Dong