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Low-dimensional mixed anion compounds Ba18F18In8S21 (1) and Barf10In4S10 (2), are synthesized and characterized. These compounds crystallize in the space group P42/ncm(138) with a = b = 22.0703(8) Å, c = 12.6143(9) Å, and V = 6144.4(6) Å3 (Z = 4) for 1 and Pnma(62) with a = 12.5686(8) Å, b = 19.2822(12) Å, c = 12.5835(9) Å, and V = 3049.6(3) Å3 (Z = 4) for 2. Compound 1 contains the unusual one-dimensional fluorite type [Ba16F18] ionic region and [BaIn8S21] covalent region, whereas 2 has a two-dimensional fluorite type [Ba2F2] block and the unique tetranuclear [In4S10]8- anion. The first principles electronic structure calculation performed with density functional theory (DFT) indicates that the two compounds are both direct band semiconductors with a gap of 2.28 eV for 1 and 2.23 eV for 2. [ABSTRACT FROM AUTHOR]

We present here the structures and magnetism of two quasi-1D linear chain compounds of BiM2BP2O10 (M = Co, Ni), which were synthesized by traditional solid-state reactions for the first time. Two title compounds crystallize in the monoclinic system with space group P21/c and feature novel 3D structures with a linear chain structure of (MO6}n further connected by [BP2O10]7- anionic groups. The results of magnetic property measurements evidence the antiferro-magnetic properties of both compounds in low magnetic field and a field-dependent metamagnetic transition from the antiferromagnetic to ferromagnetic ground state of the BiCo2BP2O10 complex. [ABSTRACT FROM AUTHOR]

Two new mid-infrared transparency compounds, centric Ba2BiGaS5 (1) and acentric Ba2BiInS5 (2), were synthesized from a high-temperature solid-state reaction in evacuated closed silica tubes. Their crystal structures were determined by a single crystal X-ray diffraction method at 293 K. The results of crystal structure solution indicate that compound 1 crystallizes in the centrosymmetric space group Pnma with trans-1∞[BiGaS5]4- chain structure, while compound 2 crystallizes in the noncentrosymmetric polar space group Cmc21 with cis-1∞[BiInS5]4- chain structure. Two types of lone-pair electrons alignment fashions within 1∞[BiMS5]4- chains result in destructive (for 1) or constructive (for 2) dipole moments, as illustrated in the crystal structures and the partial electron density maps based on the first-principles electronic structure computations. Powder second-harmonic generation (SHG) experiments with a 2.05 μm pumping laser show that the SHG efficiency of the polar compound 2 is approximately 0.8 times that of KTiOPO4 (KTP) reference. Furthermore, SHG signal intensity measurements using different size particles of powder samples indicate that compound 2 can also achieve type I phase-matching, which makes the compound promising for practical applications. [ABSTRACT FROM AUTHOR]

Two new quaternary sulfides, Ba2SbFeS5 and Ba2BiFeS5, were synthesized by using a conventional high-temperature solid-state reaction method in closed silica tubes at 1123 K. The two compounds both crystallize in the orthorhombic space group Pnma with a = 12.128(6) Å, b = 8.852(4) Å, c = 8.917(4) Å, and Z = 4 for Ba2SbFeS5 and a = 12.121(5) Å, b = 8.913(4) Å, c = 8.837(4) Å, and Z = 4 for Ba2BiFeS5. The crystal structure unit can be viewed as an infinite one-dimensional edge-shared MS5 (M = Sb, Bi) tetragonal-pyramid chain with FeS4 tetrahedra alternately arranged on two sides of the MS5 polyhedral chain via edge-sharing (so the chain can also be written as 1∞[MFeS5]4−). Interestingly, the compounds have the structural type of a Ba3FeS5 high-pressure phase considering one Ba2+ is replaced by one Sb3+/Bi3+, with Fe4+ reduced to Fe3+ for in order to maintain the electroneutrality of the system. As a result, the isolated iron ions in Ba3FeS5 are bridged by intermediate MS polyhedra in Ba2MFeS5 (M = Sb, Bi) compounds and form the 1∞[MFeS5]4− chain structure. This atom substitution of Ba2+ by one Sb3+/Bi3+ leads to a magnetic transition from paramagnetic Ba3FeS5 to antiferromagnetic Ba2MFeS5, resulting from an electron-exchange interaction of the iron ions between inter- or intrachains. Magnetic property measurements indicate that the two compounds are both antiferromagnetic materials with Neel temperatures of 13 and 35 K for Ba2SbFeS5 and Ba2BiFeS5, respectively. First-principles electronic structure calculations based on density functional theory show that the two compounds are both indirect-band semiconductors with band gaps of 0.93 and 1.22 eV for Ba2SbFeS5 and Ba2BiFeS5, respectively [ABSTRACT FROM AUTHOR]