A new chiral sulfide family, Ln(4)InSbS(9) (Ln = La, Pr, Nd), with its own structure type in space group P4(1)2(1)2 or its enantiomorph P4(3)2(1)2 has been synthesized by solid-state reaction. Remarkably, the La member shows the strongest Kleinman-forbidden second harmonic generation to date, with an intensity 1.5 times that of commercial AgGaS(2) at a laser wavelength of 2.05 μm, and exhibits type-I phase-matchable behavior. Density functional theory calculations and ab initio molecular dynamics simulations suggest that lattice vibrations may be responsible for the origin and magnitude of the strong SHG effect.

Chalcogenides are the most promising mid- and far-infrared materials for nonlinear optical (NLO) applications. Yet, most of them are sulfides and selenides, and tellurides are still rare. Herein, we report three new KCd4Ga5S12-structure type NLO-active tellurides, CsX(II)4In5Te12 (X(II) = Mn, Zn, Cd), synthesized by solid-state reactions. The structure features a 3D diamond-like framework constructed by vertex-sharing asymmetric MTe4 tetrahedra that are stacked along the c-axis. CsCd4In5Te12 exhibits the strongest powder second-harmonic generation (SHG) intensity at 2050 nm (0.61 eV) among tellurides to date, 9 × benchmark AgGaS2 in the range of 46-74 μm particle size. The primary studies reveal the 1.42 eV direct band gap and high absorption coefficient in the visible spectral region for CsCd4In5Te12, suggesting it is a new potential solar cell absorber material. In addition, CsMn4In5Te12 also displays a spin-canted antiferromagnetic property below 50 K.

Two new quaternary chalcogenides, La(4)FeSb(2)S(10) and La(4)FeSb(2)Se(10), have been synthesized from the stoichiometric mixture of elements by solid-state reactions at 1100 degrees C. The compounds crystallize in the orthorhombic space group Pbcm with a = 15.066(4) A, b = 7.590(2) A, c = 13.341(4) A, and Z = 4 and a = 15.596(5) A, b = 7.869(2) A, c = 13.960(4) A, and Z = 4, respectively. These structures represent an unique three-dimensional network, in which SbQ(3) trigonal pyramids (Sb-S < 2.60 A, Sb-Se < 2.80 A) are connected via a relatively weak Sb-Q bond (Sb-S approximately 2.90 A, Sb-Se approximately 3.00 A) in a novel teeter-totter (SbQ(4))(n) chain motif. The theoretical studies confirm the Sb-Q bonding interactions within such teeter-totter chains. Their optical band gaps are measured to be 1.00 and 0.85 eV. At room temperature, their electrical conductivities are about 10(-4) S/cm. Both compounds display antiferromagnetic interactions between Fe centers, and their effective magnetic moments are 5.25 and 6.17 micro(B), respectively.

A novel noncentrosysmmetric sulfide, Pb5Ga6ZnS15 (1), was synthesized for the first time. Its crystal structure revealed the presence of [GaS2](-)∞ (chain 1, chains of [GaS4](5-) tetrahedra) and [Ga4S9](6-)∞ (chain 2, chains of T2-supertetrahedra) connected by isolated [ZnS4](6-) tetrahedra. Structure correlation with the network constructed solely using chain 1 (Pb4Ga4GeQ12-type) is discussed. Pb5Ga6ZnS15 was calculated to have a suitable static briefringence (Δn) of 0.1137, and a large nonlinear optical susceptibility d31 of 58.32 pm V(-1) at a wavelength of 2.05 μm (0.6 eV), much higher than that of the benchmark AgGaS2 (18.14 pm V(-1)).

Four new quaternary lanthanide antimony sulfides: Ln(2)Mn(3)Sb(4)S(12) (Ln = Pr, Nd, Sm, Gd) have been synthesized from a stoichiometric element mixture at 1373 K by conventional solid state reactions. These compounds crystallize in the monoclinic space group C2/m with the unit cell parameters of a = 19.928(2)-19.9672(6) A, b = 3.9323(4)-3.8803(2) A, c = 14.921(2)-14.9011(1) A, V = 938.5(2)-925.63(6) A(3), and Z = 2 on going from Ln = Pr to Gd. Their structure represents a novel wavy MnS(6) octahedron layer decorated on both sides by chains of an SbS(5) square pyramid via strong Sb-S bonding interactions (< 3.0 A). Such a MnS(6) octahedron layer consists of chains of an edge-sharing [Mn1S(6)](2) dimer extending along [010] that are interconnected by single strings of an edge-sharing Mn2S(6) octahedron at axial S apexes. Sm(2)Mn(3)Sb(4)S(12) displays spin-canted antiferromagnetic interactions between Sm(2+) and Mn(2+) centers and an optical gap of 1.50 eV. The DFT study indicates an indirect band gap with an electronic transfer excitation of S 3p to Sb 5p orbital electrons.

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Three thioantimonides charge compensated by Ln/S/Cl cationic layers, namely centrosymmetric La8S4Cl8La12S8Cl4[SbS3]8 and non-centrosymmetric Ln12S8Cl8[SbS3]4 (Ln = La and Ce) have been discovered for the first time.

The first antimony oxychloride sulfide, namely, La3OSCl2[SbS3], has been designed by isovalent anion substitution strategy. It belongs to the polar hexagonal space group P63 mc (No. 186) with a = 9.327(5) Å, c = 7.075(5) Å, V = 533.0(5) Å3, and Z = 2. It is composed of three-dimensional (3D) cationic [La3OSCl2]3+ networks hosting covalent [SbS3] molecular anions. The 3D cationic [La3OSCl2]3+ are formed by the one-dimensional (1D) hexagonal columns of corner-shared [(Cl/S)­La3] polyhedra propagating along the 63 axis situated in (0,0,z) and [OLa3] trigonal pyramids via corner-sharing. Moreover, the alternating [SbS3] and [OLa3] trigonal pyramids are arranged along the 3-fold axis located at (1/3, 2/3, z), generating a dipole moment component along the c-direction. Another remarkable structural motif is the occurrence of the empty octahedra formed by the disordered Cl/S anions, which further share the face to form 1D chains extending along the 63 axis located at (0,0,z). Interestingly, the occurrence of the isolated [La3SbOS3]4+ cubane-like clusters instead of the “chains of [La3SbOS3]4+” make the title compound distinct from the related La4OCl2S4 featuring common chains of [La4OS3]4+. The preliminary nonlinear optical (NLO) measurement indicates a moderate second-harmonic-generation (SHG) signal (ca. 0.7 × AgGaS2) at 2050 nm laser. Moreover, calculated birefringence for La3OSCl2[SbS3] is ∼0.269 at 2050 nm. In addition, the optical energy gap of 2.5 eV for La3OSCl2[SbS3] was derived, which can be assigned to the charge transition from the highest value of valence band derived dominantly from the of S 3p states to the lowest value of conduction band mainly made up of the Sb 5p and of La 5d states.