The four isostructural compounds Li(2)In(2)MQ(6) (M = Si, Ge; Q = S, Se) have been synthesized for the first time. They crystallize in the noncentrosymmetric monoclinic space group Cc with the three-dimensional framework composed of corner-sharing LiQ(4), InQ(4), and MQ(4) tetrahedra. The second-harmonic-generation signal intensities of the two sulfides and two selenides were close to those of AgGaS(2) and AgGaSe(2), respectively, when probed with a laser with 2090 nm as the fundamental wavelength. They possess large band gaps of 3.61(2) eV for Li(2)In(2)SiS(6), 3.45(2) eV for Li(2)In(2)GeS(6), 2.54(2) eV for Li(2)In(2)SiSe(6), and 2.30(2) eV for Li(2)In(2)GeSe(6), respectively. Moreover, these four compounds all melt congruently at relatively low temperatures, which makes it feasible to grow bulk crystals needed for practical application by the Bridgman-Stockbarger method.

The twelve quaternary rare-earth selenides Ba(2)MLnSe5 (M = Ga, In; Ln = Y, Nd, Sm, Gd, Dy, Er) have been synthesized for the first time. The compounds Ba(2)GaLnSe(5) (Ln = Y, Nd, Sm, Gd, Dy, Er) are isostructural and crystallize in a new structure type in the centrosymmetric space group P ̅1 of the triclinic system while the isostructural compounds Ba(2)InLnSe(5) (Ln = Y, Nd, Sm, Gd, Dy, Er) belong to the Ba(2)BiInS(5) structure type and crystallize in the noncentrosymmetric space group Cmc2(1) of the orthorhombic system. The structures contain infinite one-dimensional anionic chains (1)(∞)[GaLnSe(5)](4-) and (1)(∞)[InLnSe(5)](4-), and both chains are built from LnSe(6) octahedra and MSe(4) (M = Ga, In) tetrahedra in the corresponding selenides. As deduced from the diffuse reflectance spectra, the band gaps of most Ba(2)MLnSe(5) (M = Ga, In; Ln = Y, Nd, Sm, Gd, Dy, Er) compounds are around 2.2 eV. The magnetic susceptibility measurements on Ba(2)GaGdSe(5) and Ba(2)InLnSe(5) (Ln = Nd, Gd, Dy, Er) indicate that they are paramagnetic and obey the Curie-Weiss law, while the magnetic susceptibility of Ba(2)InSmSe(5) deviates from the Curie-Weiss law as a result of the crystal field splitting. Furthermore, Ba(2)InYSe(5) exhibits a strong second harmonic generation response close to that of AgGaSe(2), when probed with the 2090 nm laser as fundamental wavelength.

A new ternary selenostannate Ba6Sn6Se13 has been synthesized by a high temperature solid-state method. The compound crystallizes in the non-centrosymmetric orthorhombic space group P2(1)2(1)2(1) and may be represented as Ba6Sn5(2+)Sn(4+)Se13 with mixed valence Sn atoms. Sn(4+) cations lie in a tetrahedral environment, while Sn(2+) cations are found in two kinds of coordination environments: the trigonal pyramid and quadrangular pyramid. SnSe(n) (n = 3, 4, 5) polyhedra are further connected to generate a three-dimensional framework with Ba(2+) residing in cavities. Ba6Sn6Se13 shows moderate nonlinear optical response and is the first reported NLO compound in the Ba-Sn-Se system. In addition, diffuse reflectance spectroscopy measurement indicates that the band gap of Ba6Sn6Se13 is 1.52(2) eV and thermal analysis suggests that the compound melts incongruently. The theoretically calculated SHG response and band gap are in good agreement with experimental results.

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The 12 new rare-earth tellurides Ba(2)MLnTe(5) (M = Ga and Ln = Sm, Gd, Dy, Er, Y; M = In and Ln = Ce, Nd, Sm, Gd, Dy, Er, Y) have been synthesized by solid-state reactions. The two compounds Ba(2)GaLnTe(5) (Ln = Sm, Gd) are isostructural and crystallize in the centrosymmetric space group P1, while the other 10 compounds belong to another structure type in the noncentrosymmetric space group Cmc2(1). In both structure types, there are one-dimensional anionic (1)(∞)[MLnTe(5)](4-) chains built from LnTe(6) octahedra and MTe(4) (M = Ga, In) tetrahedra, but the connectivity between the LnTe(6) octahedra and MTe(4) tetrahedra is different for the two structure types. On the basis of the diffuse-reflectance spectra, the band gaps are around 1.1-1.3 eV for these compounds. The Ba(2)MLnTe(5) (M = Ga and Ln = Gd, Dy; M = In and Ln = Gd, Dy, Er) compounds are paramagnetic and obey the Curie-Weiss law, while the magnetic susceptibility of Ba(2)InSmTe(5) deviates from the Curie-Weiss law. In addition, electronic structure calculation on Ba(2)MYTe(5) (M = Ga, In) indicates that they are both direct-gap semiconductors with large nonlinear-optical coefficients.

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A new barium ytterbium indium selenide, Ba2YbInSe5, was obtained by conventional high temperature solid state reaction. The compound crystallizes in the noncentrosymmetric space group Cmc21 of the orthorhombic system. The structure contains infinite one‐dimensional anionic chains 1∞[YbInSe5]4–, which are built from YbSe6 octahedra and InSe4 tetrahedra and separated by Ba2+ cation. The magnetic measurement indicates that the compound is paramagnetic. In addition, the calculated bandgap is 0.29 eV.