Crystal structure and physical properties of the quaternary manganese-bearing pavonite homologue Mn1.34Sn6.66Bi8Se20

The quaternary manganese tin bismuth selenide, Mn_1.34Sn_6.66Bi₈Se₂₀ was synthesized by combining constituent elements at 723 K. Single crystal structure determination revealed that Mn_1.34Sn_6.66Bi₈Se₂₀ is isostructural to the mineral pavonite, AgBi₃S₅, crystallizing in the monoclinic space group C2/m (#12) with a=13.648(3) Å; b=4.175(1) Å; c=17.463(4) Å; β=93.42(3)°. In the structure, two kinds of layered modules, denoted A and B, alternate along [0 0 1]. Module A consists of paired chains of face-sharing monocapped trigonal prisms (around Bi/Sn) separated by a single chain of edge-sharing octahedra (around Mn/Sn). Module B represents a NaCl-type fragment of edge-sharing [(Bi/Sn)Se₆] octahedra. Mn_1.34Sn_6.66Bi₈Se₂₀ is an n-type narrow gap semiconductor with E_g∼0.29 eV. At 300 K, thermopower, electrical conductivity and lattice thermal conductivity values are −123 μV/K, 47 S/cm and 0.6 W/m K, respectively. Mn_1.34Sn_6.66Bi₈Se₂₀ is paramagnetic at high temperatures and undergoes antiferromagnetic transition at T_N=10 K.     

Synthesis and characterization of quaternary selenides Sn2Pb5Bi4Se13 and Sn8.65Pb0.35Bi4Se15

Quaternary selenides Sn₂Pb₅Bi₄Se₁₃ and Sn_8.65Pb_0.35Bi₄Se₁₅ were synthesized from the elements in sealed silica tubes; their crystal structures were determined by single-crystal and powder X-ray diffraction. Both compounds crystallize in monoclinic space group C2/m (No.12), with lattice parameters of Sn₂Pb₅Bi₄Se₁₃: a = 14.001(6) Å, b = 4.234(2) Å, c = 23.471(8) Å, V = 1376.2(1) Å³, R₁/wR₂ = 0.0584/0.1477, and GOF = 1.023; Sn_8.65Pb_0.35Bi₄Se₁₅: a = 13.872(3) Å, b = 4.2021(8) (4) Å, c = 26.855(5) Å, V = 1557.1(5) Å³, R₁/wR₂ = 0.0506/0.1227, and GOF = 1.425. These compounds exhibit tropochemical cell-twinning of NaCl-type structures with lillianite homologous series L(4, 5) and L(4, 7) for Sn₂Pb₅Bi₄Se₁₃ and Sn_8.65Pb_0.35Bi₄Se₁₅, respectively. Measurements of electrical conductivity indicate that these materials are semiconductors with narrow band gaps; Sn₂Pb₅Bi₄Se₁₃ is n-type, whereas Sn_8.65Pb_0.35Bi₄Se₁₅ is a p-type semiconductor with Seebeck coefficients −80(5) and 178(7) μV/K at 300 K, respectively.     

Hydrothermal synthesis of [C6H16N2][In2Se3(Se2)]: A new one-dimensional indium selenide

A new organically templated indium selenide, [C₆H₁₆N₂][In₂Se₃(Se₂)], has been prepared hydrothermally from the reaction of indium, selenium and trans-1,4-diaminocyclohexane in water at 170 °C. This material was characterised by single-crystal and powder X-ray diffraction, thermogravimetric analysis, UV-vis diffuse reflectance spectroscopy, FT-IR and elemental analysis. The compound crystallises in the monoclinic space group C2/c (a=12.0221(16) Å, b=11.2498(15) Å, c=12.8470(17) Å, β=110.514(6)°). The crystal structure of [C₆H₁₆N₂][In₂Se₃(Se₂)] contains anionic chains of stoichiometry [In₂Se₃(Se₂)]²⁻, which are aligned parallel to the [1 0 1] direction, and separated by diprotonated trans-1,4-diaminocyclohexane cations. The [In₂Se₃(Se₂)]²⁻ chains, which consist of alternating four-membered [In₂Se₂] and five-membered [In₂Se₃] rings, contain perselenide (Se₂)²⁻ units. UV-vis diffuse reflectance spectroscopy indicates that [C₆H₁₆N₂][In₂Se₃(Se₂)] has a band gap of 2.23(1) eV.     

Quaternary selenostannates Na2−xGa2−xSn1+xSe6 and AGaSnSe4 (A=K, Rb, and Cs) through rapid cooling of melts. Kinetics versus thermodynamics in the polymorphism of AGaSnSe4

The quaternary alkali-metal gallium selenostannates, Na_2−xGa_2−xSn_1+xSe₆ and AGaSnSe₄ (A=K, Rb, and Cs), were synthesized by reacting alkali-metal selenide, Ga, Sn, and Se with a flame melting-rapid cooling method. Na_2−xGa_2−xSn_1+xSe₆ crystallizes in the non-centrosymmetric space group C2 with cell constants a=13.308(3) Å, b=7.594(2) Å, c=13.842(3) Å, β=118.730(4)°, V=1226.7(5) Å³. α-KGaSnSe₄ crystallizes in the tetragonal space group I4/mcm with a=8.186(5) Å and c=6.403(5) Å, V=429.1(5) Å³. β-KGaSnSe₄ crystallizes in the space group P2₁/c with cell constants a=7.490(2) Å, b=12.578(3) Å, c=18.306(5) Å, β=98.653(5)°, V=1705.0(8) Å³. The unit cell of isostructural RbGaSnSe₄ is a=7.567(2) Å, b=12.656(3) Å, c=18.277(4) Å, β=95.924(4)°, V=1741.1(7) Å³. CsGaSnSe₄ crystallizes in the orthorhombic space group Pmcn with a=7.679(2) Å, b=12.655(3) Å, c=18.278(5) Å, V=1776.1(8) Å³. The structure of Na_2−xGa_2−xSn_1+xSe₆ consists of a polar three-dimensional network of trimeric (Sn,Ga)₃Se₉ units with Na atoms located in tunnels. The AGaSnSe₄ possess layered structures. The compounds show nearly the same Raman spectral features, except for Na_2−xGa_2−xSn_1+xSe₆. Optical band gaps, determined from UV-Vis spectroscopy, range from 1.50 eV in Na_2−xGa_2−xSn_1+xSe₆ to 1.97 eV in CsGaSnSe₄. Cooling of the melts of KGaSnSe₄ and RbGaSnSe₄ produces only kinetically stable products. The thermodynamically stable product is accessible under extended annealing, which leads to the so-called γ-form (BaGa₂S₄-type) of these compounds.     

Formation and structural refinements of tunneled intergrowth phases in the Ga2O3-In2O3-SnO2-TiO2 system

Over 100 samples were prepared as (Ga,In)₄(Sn,Ti)_n−4O_2n−2, n=6, 7, and 9 by solid-state reaction at 1400 °C and characterized by X-ray diffraction. Nominally phase-pure beta-gallia-rutile intergrowths were observed in samples prepared with n=9 (0.17?x?0.35 and 0?y?0.4) as well as in a few samples prepared with n=6 and 7. Rietveld analysis of neutron time-of-flight powder diffraction data were conducted for three phase-pure samples. The n=6 phase Ga_3.24In_0.76Sn_1.6Ti_0.4O₁₀ is monoclinic, P2/m, with Z=2 and a=11.5934(3) Å, b=3.12529(9) Å, c=10.6549(3) Å, β=99.146(1)°. The n=7 phase Ga_3.24In_0.76Sn_2.4Ti_0.6O₁₂ is monoclinic, C2/m, with Z=2 and a=14.2644(1) Å, b=3.12751(2) Å, c=10.6251(8) Å, β=108.405(1)°. The n=9 phase Ga_3.16In_0.84Sn₄TiO₁₆ is monoclinic, C2/m, with Z=2 a=18.1754(2) Å, b=3.13388(3) Å, c=10.60671(9) Å, β=102.657(1)°. All of the structures are similar in that they possess distorted hexagonal tunnels parallel to the [010] vector.     

Comparative high-pressure study and chemical bonding analysis of Rh3Bi14 and isostructural Rh3Bi12Br2

The binary compound Rh₃Bi₁₄ was synthesized from the elements. The compound is isostructural with Rh₃Bi₁₂Br₂, crystallizes with the orthorhombic space group Fddd (no. 70) and lattice parameters a=6.8959(15) Å, b=17.379(3) Å, c=31.758(6) Å. The crystal structure consists of a three-dimensional (3D) framework of edge-sharing cubes and square antiprisms (RhBi_8/2). It is closely related to the intermetallic compound RhBi₄, in which two Y-like frameworks of antiprisms interpenetrate. In Rh₃Bi₁₄ and Rh₃Bi₁₂Br₂, additional bismuth and bromine anions, respectively, fill the channels of the 3D polyhedral framework formed by covalently bonded rhodium and bismuth atoms. High-pressure X-ray powder diffraction data from synchrotron measurements of Rh₃Bi₁₄ and Rh₃Bi₁₂Br₂ indicate a high stability of both compounds in the investigated range from ambient pressure to ca. 30 GPa at ambient temperature.     

Synthesis crystal structure and ionic conductivity of Ca0.5Bi3V2O10 and Sr0.5Bi3V2O10

Two new compounds Ca_0.5Bi₃V₂O₁₀ and Sr_0.5Bi₃V₂O₁₀ have been synthesized in the ternary system: MO-Bi₂O₃-V₂O₅ system (M=M²⁺). The crystal structure of Sr_0.5Bi₃V₂O₁₀ has been determined from single crystal X-ray diffraction data, space group and Z=2, with cell parameters a=7.1453(3) Å, b=7.8921(3) Å, c=9.3297(3) Å, α=106.444(2)°, β=94.088(2)°, γ=112.445(2)°, V=456.72(4) Å³. Ca_0.5Bi₃V₂O₁₀ is isostructural with Sr_0.5Bi₃V₂O₁₀, with, a=7.0810(2) Å, b=7.8447(2) Å, c=9.3607(2) Å, α=106.202(1)°, β=94.572(1)°, γ=112.659(1)°, V=450.38(2) Å³ and its structure has been refined by Rietveld method using powder X-ray data. The crystal structure consists of infinite chains of (Bi₂O₂) along c-axis formed by linkage of BiO₈ and BiO₆ polyhedra interconnected by MO₈ polyhedra forming 2D layers in ac plane. The vanadate tetrahedra are sandwiched between these layers. Conductivity measurements give a maximum conductivity value of 4.54×10⁻⁵ and 3.63×10⁻⁵ S cm⁻¹ for Ca_0.5Bi₃V₂O₁₀ and Sr_0.5Bi₃V₂O₁₀, respectively at 725 °C.     

Syntheses, structures, optical properties, and theoretical calculations of Cs2Bi2ZnS5, Cs2Bi2CdS5, and Cs2Bi2MnS5

Three new compounds, Cs₂Bi₂ZnS₅, Cs₂Bi₂CdS₅, and Cs₂Bi₂MnS₅, have been synthesized from the respective elements and a reactive flux Cs₂S₃ at 973 K. The compounds are isostructural and crystallize in a new structure type in space group Pnma of the orthorhombic system with four formula units in cells of dimensions at 153 K of a=15.763(3), b=4.0965(9), c=18.197(4) Å, V=1175.0(4) Å³ for Cs₂Bi₂ZnS₅; a=15.817(2), b=4.1782(6), c=18.473(3)  Å, V=1220.8(3)  ų for Cs₂Bi₂CdS₅; and a=15.830(2), b=4.1515(5), c=18.372(2) Å, V=1207.4(2) Å³ for Cs₂Bi₂MnS₅. The structure is composed of two-dimensional _∞²[Bi₂MS₅²⁻] (M=Zn, Cd, Mn) layers that stack perpendicular to the [100] axis and are separated by Cs⁺ cations. The layers consist of edge-sharing _∞¹[Bi₂S₆⁶⁻] and _∞¹[MS₃⁴⁻] chains built from BiS₆ octahedral and MS₄ tetrahedral units. Two crystallographically unique Cs atoms are coordinated to S atoms in octahedral and monocapped trigonal prismatic environments. The structure of Cs₂Bi₂MS₅, is related to that of Na₂ZrCu₂S₄ and those of the AMM′Q₃ materials (A=alkali metal, M=rare-earth or Group 4 element, M′= Group 11 or 12 element, Q=chalcogen). First-principles theoretical calculations indicate that Cs₂Bi₂ZnS₅ and Cs₂Bi₂CdS₅ are semiconductors with indirect band gaps of 1.85 and 1.75 eV, respectively. The experimental band gap for Cs₂Bi₂CdS₅ is ≈1.7 eV, as derived from its optical absorption spectrum.     

Synthesis of Bi2Se3 thermoelectric nanosheets and nanotubes through hydrothermal co-reduction method

Bi₂Se₃ nanosheets and nanotubes were prepared by a hydrothermal co-reduction method at 150, 180, 200, and 210 °C. Bi₂Se₃ nanosheets, nanobelts and nanotubes were obtained. The Bi₂Se₃ nanoflakes are 50-500 nm in width and 2-5 nm in thickness. The Bi₂Se₃ nanotubes are 5-10 nm in diameter, 80-120 nm in length, and 1.3 nm in wall thickness. X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and electron diffraction were employed to characterize the products. Experimental results showed that the nanosheets and the nanotubes are hexagonal in structure with a=4.1354 Å and c=27.4615 Å. A possible formation and crystal growth mechanism of Bi₂Se₃ nanostructures is proposed.     

Synthesis and phase width of new quaternary selenides PbxSn6−xBi2Se9 (x=0-4.36)

Quaternary chalcogenides Pb_xSn_6−xBi₂Se₉ (x=0-4.36) were synthesized with solid-state methods; their structures were determined from the X-ray diffraction of single crystals. Pb_xSn_6−xBi₂Se₉ crystallizes in an orthorhombic space group Cmcm (No. 63); the structure features a three-dimensional framework containing slabs of NaCl-(3 1 1) type that exhibits identical layers containing seven octahedra units, which expand along the direction [0 1 0]. Each slab contains fused rectangular units that are connected to each other with M-Se contacts in a distorted octahedral environment. Calculations of the band structure, measurements of Seebeck coefficient and electrical conductivity confirm that these compounds are n-type semiconductors with small band gaps and large electrical conductivities.     

Yb3Cu6Sn5, Yb5Cu11Sn8 and Yb3Cu8Sn4: crystal structure of three ordered compounds

Yb₃Cu₆Sn₅, Yb₅Cu₁₁Sn₈ and Yb₃Cu₈Sn₄ compounds were prepared in sealed Ta crucibles by induction melting and subsequent annealing. The crystal structures of Yb₃Cu₆Sn₅ and Yb₅Cu₁₁Sn₈ were determined from single crystal diffractometer data: Yb₃Cu₆Sn₅, isotypic with Dy₃Co₆Sn₅, orthorhombic, Immm, oI28, a=4.365(1) Å, b=9.834(3) Å, c=12.827(3) Å, Z=2, R=0.019, 490 independent reflections, 28 parameters; Yb₅Cu₁₁Sn₈ with its own structure, orthorhombic, Pmmn, oP48, a=4.4267(6) Å, b=22.657(8) Å, c=9.321(4) Å, Z=2, R=0.047, 1553 independent reflections, 78 parameters. Both compounds belong to the BaAl₄-derived defective structures, and are closely related to Ce₃Pd₆Sb₅ (oP28, Pmmn). The crystal structure of Yb₃Cu₈Sn₄, isotypic with Nd₃Co₈Sn₄, was refined from powder data by the Rietveld method: hexagonal, P6₃mc, hP30, a=9.080(1) Å, c=7.685(1) Å, Z=2, R_wp=0.040. It is an ordered substitution derivative of the BaLi₄ type (hP30, P6₃/mmc). All compounds show strong Cu-Sn bonds with a length reaching 2.553(3) Å in Yb₅Cu₁₁Sn₈.     

Rb2BaNb2Se11: A new quaternary niobium polyselenide with infinite anionic chains composed of Nb2Se11 building block

The quaternary compound Rb₂BaNb₂Se₁₁ has been synthesized by reacting Nb metal with an in situ formed flux of Rb₂Se₃, BaSe and Se at 773 K. Rb₂BaNb₂Se₁₁ crystallizes in the monoclinic space group P2₁/c with four formula units and lattice parameters a=7.8438(5) Å, b=13.6959(6) Å, c=17.0677(13) Å, β=97.917(9)°. The structure consists of one-dimensional anionic chains formed by interconnection of dimeric [Nb₂Se₁₁] units. The chains are directed along the crystallographic c-axis with Rb⁺ and Ba²⁺ ions being located between the chains. The [Nb₂Se₁₁] units are formed by face sharing of two NbSe₇ bipyramids and are joined by Se₂²⁻ dianions to form infinite ¹_∞[Nb₂Se₁₁⁴⁻] chains. The compound was characterized with infrared spectroscopy in the FIR region, Raman and UV/Vis diffuse reflectance spectroscopy.     

The structural investigation of Ba4Bi3F17

The anion-excess ordered fluorite-related phase Ba₄Bi₃F₁₇ has been synthesized by a solid state reaction of BaF₂ and BiF₃ at 873 K. The crystal structure of Ba₄Bi₃F₁₇ has been studied using electron diffraction and X-ray powder diffraction (a=11.2300(2) Å, c=20.7766(5) Å, S.G. , R_I=0.020, R_P=0.036). Interstitial fluorine atoms in the Ba₄Bi₃F₁₇ structure are considered to form isolated cuboctahedral 8 : 12 : 1 clusters. The structural relationship between Ba₄Bi₃F₁₇ and similar rare-earth-based phases is discussed.     

Subsolidus phase relations and crystal structures of the mixed-oxide phases in the In2O3-WO3 system

Subsolidus phase relationships in the In₂O₃-WO₃ system at 800-1400°C were investigated using X-ray diffraction. Two binary-oxide phases—In₆WO₁₂ and In₂(WO₄)₃—were found to be stable over the range 800-1200°C. Heating the binary-oxide phases above 1200°C resulted in the preferential volatilization of WO₃. Rietveld refinement was performed on three structures using X-ray diffraction data from nominally phase-pure In₆WO₁₂ at room temperature and from nominally phase-pure In₂(WO₄)₃ at 225°C and 310°C. The indium-rich phase, In₆WO₁₂, is rhombohedral, space group (rhombohedral), with Z=1, a=6.22390(4) Å, α=99.0338(2)° [hexagonal axes: a_H=9.48298(6) Å, c=8.94276(6) Å, a_H/c=0.9430(9)]. In₆WO₁₂ can be viewed as an anion-deficient fluorite structure in which 1/7 of the fluorite anion sites are vacant. Indium tungstate, In₂(WO₄)₃, undergoes a monoclinic-orthorhombic transition around 250°C. The high-temperature polymorph is orthorhombic, space group Pnca, with a=9.7126(5) Å, b=13.3824(7) Å, c=9.6141(5) Å, and Z=4. The low-temperature polymorph is monoclinic, space group P2₁/a, with a=16.406(2) Å, b=9.9663(1) Å, c=19.099(2) Å, β=125.411(2)°, and Z=8. The structures of the two In₂(WO₄)₃ polymorphs are similar, consisting of a network of corner sharing InO₆ octahedra and WO₄ tetrahedra.     

Two new octahedral/pyramidal frameworks containing both cation channels and lone-pair channels: syntheses and structures of Ba2MnMn2(SeO3)6 and PbFe2(SeO3)4

The hydrothermal syntheses, single crystal structures, and some properties of Ba₂Mn^IIMn₂^III(SeO₃)₆ and PbFe₂(SeO₃)₄ are reported. These related phases contain three-dimensional frameworks of vertex (FeO₆) and vertex/edge linked (MnO₆) octahedra and SeO₃ pyramids. In each case, the MO₆/SeO₃ framework encloses two types of 8 ring channels, one of which encapsulates the extra-framework cations and one of which provides space for the Se^IV lone pairs. Crystal data: Ba₂Mn₃(SeO₃)₆, M_r=1201.22, monoclinic, P2₁/c (No. 14), a=5.4717 (3) Å, b=9.0636 (4) Å, c=17.6586 (9) Å, β=94.519 (1)°, V=873.03 (8) Å³, Z=2, R(F)=0.031, wR(F²)=0.070; PbFe₂(SeO₃)₄, M_r=826.73, triclinic, (No. 2), a=5.2318 (5) Å, b=6.7925 (6) Å, c=7.6445 (7) Å, α=94.300 (2)°, β=90.613 (2)°, γ=95.224 (2)°, V=269.73 (4) Å³, Z=1, R(F)=0.051, wR(F²)=0.131.     

Yb3CoSn6 and Yb4Mn2Sn5: New polar intermetallics with 3D open-framework structures

Two new ternary ytterbium transition metal stannides, namely, Yb₃CoSn₆ and Yb₄Mn₂Sn₅, have been obtained by solid-state reactions of the corresponding pure elements in welded tantalum tubes at high temperature. Their crystal structures have been established by single-crystal X-ray diffraction studies. Yb₃CoSn₆ crystallizes in the orthorhombic space group Cmcm (no. 63) with cell parameters of a=4.662(2), b=15.964(6), c=13.140(5) Å, V=978.0(6) Å³, and Z=4. Its structure features a three-dimensional (3D) open-framework composed of unusual [CoSn₃] layers interconnected by zigzag Sn chains, forming large tunnels along the c-axis which are occupied by the ytterbium cations. Yb₄Mn₂Sn₅ is monoclinic space group C2/m (no. 12) with cell parameters of a=16.937(2), b=4.5949(3), c=7.6489(7) Å, β=106.176(4)°, V=571.70(8) Å³, and Z=2. It belongs to the Mg₅Si₆ structure type and its anionic substructure is composed of parallel [Mn₂Sn₂] ladders interconnected by unusual zigzag [Sn₃] chains, forming large tunnels along the c-axis, which are filled by the ytterbium cations. Band structure calculations based on density function theory methods were also made for both compounds.     

Crystal and electronic structure of the red semiconductor Ba4LaSbGe3Se13 comprising the complex anion [Ge2Se7-Sb2Se4-Ge2Se7]

Ba₄LaGe₃SbSe₁₃ was prepared by reacting the elements under exclusion of air at 700°C, followed by slow cooling to room temperature. It crystallizes in a new type of the monoclinic space group P2₁/c, with lattice dimensions of a=1633.30(9) pm, b=1251.15(7) pm, c=1303.21(7) pm, β=103.457(2)°, V=2590.0(2) 10⁶ pm³ (Z=4). The structure contains isolated GeSe₄ as well as Ge₂Se₇ digermanate units. Two of the latter are interconnected via an Sb₂Se₄ bridge yielding an almost linear complex anion [Ge₂Se₇-Sb₂Se₄-Ge₂Se₇]¹⁴⁻. The oxidation states are assigned to be Ba^II, La^III, Ge^IV, Sb^III, and Se^−II, in accord with an electronically saturated nonmetal. The lone pair of Sb^III reflects itself in highly irregular Se coordination. The red color of the material is indicative of semiconducting behavior with an activation energy of 2.0 eV. Electronic structure calculations based on the LMTO approximation point to a smaller gap, typical for this calculation method. We utilized the COHP tool to explore the bonding character of the different Sb-Se interactions.     

Preparation and crystal structure of [Bi3I(C4H8O3H2)2(C4H8O3H)5]2Bi8I30 containing the novel polynuclear [Bi8I30] anion

Preparation and crystal structure of the novel compound [Bi₃I(C₄H₈O₃H₂)₂(C₄H₈O₃H)₅]₂Bi₈I₃₀ are reported. The title compound is prepared by heating of BiI₃ and diethylene glycol at 413 K in a sealed quartz glass tube filled with argon. Deep red single crystals are grown and applied to perform X-ray powder diffraction and X-ray single-crystal diffraction measurements. The compound crystallizes triclinic with space group P-1: Z=2, a=13.217(1) Å, b=15.277(1) Å, c=22.498(1) Å, α=84.33(1), β=73.18(1), γ=67.48(1). [Bi₃I(C₄H₈O₃H₂)₂(C₄H₈O₃H)₅]₂Bi₈I₃₀ comprises the novel polynuclear [Bi₈I₃₀]⁶⁻ anion and [Bi₃I(C₄H₈O₃H₂)₂(C₄H₈O₃H)₅]³⁺ as the cation. Cation as well as the anion can be assumed to represent intermediates between solid BiI₃ and BiI₃ completely dissolved in diethylene glycol.     

Bi3In4S10 and Bi14.7In11.3S38: Two new bismuth sulfides with interesting Bi-Bi bonding

Two new ternary bismuth chalcogenides, Bi₃In₄S₁₀ and Bi_14.7In_11.3S₃₈, were synthesized from the reactions of binary sulfides via a two-step flux technique. Single-crystal X-ray diffraction analyses indicate that Bi₃In₄S₁₀ crystallizes in the non-centrosymmetric space group Pm and Bi_14.7In_11.3S₃₈ crystallizes in the centrosymmetric space group P2₁/m. Both compounds adopt three-dimensional frameworks. A distinct structural feature in the two structures is the presence of chains of Bi atoms with alternating short Bi-Bi bonds of around 3.1 Å and longer distances of around 4.6 Å. The optical band gaps of 1.42(2) eV for Bi₃In₄S₁₀ and 1.45(2) eV for Bi_14.7In_11.3S₃₈ were deduced from the diffuse reflectance spectra.     

Hydrothermal synthesis and structure of the first tin(II) squarate Sn2O(C4O4)(H2O)—comparison with Sn2[Sn2O2F4]

A tin(II) squarate Sn₂O(C₄O₄)(H₂O) was synthesized by hydrothermal technique. It crystallizes in the monoclinic system, space group C2/m (no. 12) with lattice parameters a=12.7380(9) Å, b=7.9000(3) Å, c=8.3490(5) Å, β=121.975(3)°, V=712.69(7) Å³, Z=4. The crystal structure determined with an R=0.042 factor, consists of [(Sn₄O₁₀)(H₂O)₂] units connected from one another in the [101] and [010] directions via squarate groups to form layers separated by Sn(II) lone pairs. This compound presents the same remarkable structural arrangement as observed in the tin-oxo-fluoride Sn₂[Sn₂O₂F₄] inorganic compound with Sn(II) lone pairs E(1) and E(2) concentrated in large rectangular-shape tunnels running along [001] direction.