The preparation and crystal structures of BiReO4 and BiRe2O6

The crystal structures of two new oxides, BiReO₄ and BiRe₂O₆, have been determined by single-crystal X-ray methods using an Enraf-Nonius CAD-4F diffractometer. BiReO₄ crystallizes as red metallic needles in the space group Cmcm, cell dimensions a = 3.839(1) Å, b = 14.914(2) Å, c = 5.534(1) Å, Z = 4. The structure consists of sheets of corner-shared octahedra (composition ReO₄) linked by Bi atoms (R = 2.55%). BiRe₂O₆ crystallizes as black metallic plates in the space group C2/m, cell dimensions a = 5.516(1) Å, b = 4.906(1) Å, c = 8.384(1) Å, β = 106.71(1)°, Z =2. The structure consists of layers containing Re₂O₁₀ units linked together by corner sharing of the octahedra, alternating with layers of Bi atoms (R = 2.61%). The structure is disordered due to the random stacking of the Re layers. The Re---Re distance of 2.5 Å in the Re₂O₁₀ unit is comparable to that found in similar compounds. Both compounds exhibit stereochemically active lone pairs.     

The Phosphoniobate RbNb2PO8: An Ordered Substitution of PO4 Tetrahedra for NbO6 Octahedra in the HTB Structure

A new phosphoniobate, RbNb₂PO₈, with an intersecting tunnel structure, has been synthesized. It crystallizes in the Pnma space group with a = 13.815(1) Å, b = 15.884(2) Å, c = 12.675(2) Å, and Z = 16. The full matrix least-squares refinement led to R = 0.041 and R_w = 0.050. The host lattice is derived directly from that of the hexagonal tungsten bronzes (HTB) by an ordered substitution of PO₄ tetrahedra, forming two sorts of tunnels running along b and a, respectively, where the Rb⁺ ions are located. The first type of tunnel results from the stacking of six-sided HTB-type rings (5NbO₆ octahedra + 1PO₄ tetrahedron) with seven-sided rings (4NbO₆ octahedra + 3PO₄ tetrahedra), whereas the second type of tunnel consists of brownmillerite rings (4NbO₆ octahedra + 2 PO₄ tetrahedra).     

Hydrothermal Syntheses, Structures, and Properties of Two New Potassium Vanadium Phosphates: K3(VO) (V2O3) (PO4)2(HPO4) and K3 (VO) (HV2O3) (PO4)2(HPO4)

Two new potassium vanadium phosphates have been prepared and their structures have been determined from analysis of single crystal X-ray data. The two compounds, K₃(VO)(V₂O₃) (PO₄)₂(HPO₄) and K₃(VO)(HV₂O₃)(PO₄)₂(HPO₄), are isostructural, except for the incorporation of an extra hydrogen atom into the nearly identical frameworks. The structures consist of a three-dimensional network of [VO]_n chains connected through phosphate groups to a [V₂O₃] moiety. Magnetic susceptibility experiments indicate that in the case of the di-hydrogen compound, there are no significant magnetic interactions between the three independent vanadium (IV) centers. Crystal data: for K₃(VO)(V₂O₃)(PO₄)₂ (HPO₄), M_r = 620.02, orthorhombic space group Pnma (No. 62), a = 7.023(4) Å, b = 13.309(7) Å, c = 14.294(7) Å, V = 1336(2) ų, Z = 4, R = 5.02%, and R_w = 5.24% for 1238 observed reflections [I > 3σ(I)]; for K₃(VO)(HV₂O₃)(PO₄)₂(HPO₄), M_r = 621.04, orthorhombic space group Pnma (No. 62), a = 6.975(3) Å, b = 13.559(7) Å, c = 14.130(7) Å, V = 1336(1) ų, Z = 4, R = 6.02%, and R_w = 6.34% for 1465 observed reflections [I > 3σ(I)].     

Single-crystal characterization of Co7(OH)6(H2O)3(C4H4O4)47H2O; A new cobalt succinate identified through high-throughput synthesis

A new form of cobalt succinate has been discovered using high-throughput methods and its structure was solved by single crystal X-ray diffraction. Co₇(C₄H₄O₄)₄(OH)₆(H₂O)₃7H₂O crystallizes in the monoclinic space group P2₁/c with cell parameters: a=7.888(2) Å, b=19.082(6) Å, c=23.630(7) Å, β=91.700(5)°, V=3555(2) Å³, R₁=0.0469. This complex structure, containing 55 crystallographically distinct non-hydrogen atoms, is compared to the previously reported nickel phase, characterized using ab initio structure solution from synchrotron powder diffraction data.     

Vanadium(II) alkyls. Synthesis and X-ray crystal structures of trans-VMe2(dmpe)2 and cis-V(CH2SiMe3) 2(dmpe)2

Treatment of the vanadium(II) tetrahydroborate complex trans-V(η¹-BH₄)₂(dmpe)₂ with (trimethylsilyl) methyllithium gives the new vanadium(II) alkyl cis-V(CH₂SiMe₃)₂(dmpe)₂, where dmpe is the chelating diphosphine 1,2-bis(dimethylphosphino)ethane. Interestingly, this complex could not be prepared from the chloride starting material VCl₂(dmpe)₂. The CH₂SiMe₃ complex has a magnetic moment of 3.8 μ_B, and has been characterized by ¹H NMR and EPR spectroscopy. The cis geometry of the CH₂SiMe₃ complex is somewhat unexpected, but in fact the structure can be rationalized on steric grounds. The X-ray crystal structure of cis-V(CH₂SiMe₃)₂(dmpe)₂ is described along with that of the related vanadium(II) alkyl complex trans-VMe₂(dmpe)₂. Comparisons of the bond distances and angles for VMe₂(dmpe) ₂, V---C = 2.310(5) Å, V---P = 2.455(5) Å, and P---V---P = 83.5(2)° with those of V(CH₂SiMe₃)₂(dmpe)₂, V---C = 2.253(3) Å, V---P = 2.551(1) Å, and P ---V---P = 79.37(3)° show differences due to the differing trans influences of alkyl and phosphine ligands, and due to steric crowding in latter molecule. The V---P bond distances also suggest that metal-phosphorus π-back bonding is important in these early transition metal systems. Crystal data for VMe₂(dmpe)₂ at 25°C: space group P2₁/n, with a = 9.041(1) Å, b = 12.815(2) Å, c = 9.905(2) Å, β = 93.20(1)°, V = 1145.8(5) ų, Z = 2, R_F = 0.106, and R_wF =0.127 for 74 variables and 728 data for which I 2.58 σ(I); crystal data for V(CH₂SiMe₃)₂(dmpe)₂ at −75°C: space group C2/c, with a = 9.652(4) Å, b = 17.958(5) Å, c = 18.524(4) Å, β = 102.07(3)°, V= 3140(3) ų, Z = 4, R_F = 0.033, and R_wF = 0.032 for 231 variables and 1946 data for which I 2.58 σ(I).     

Preparation and Structure of Cerium Titanates Ce2TiO5, Ce2TiO7, and Ce4Ti9O24

Compounds Ce₂TiO₅, Ce₂Ti₂O₇, and Ce₄Ti₉O₂₄ were prepared by heating appropriate mixtures of solids containing Ce⁴⁺ and Ti³⁺ or Ti which were placed in a platinum-silica-ampoule combination at T = 1250°C (3d) under vacuum. The new compounds were characterized by powder patterns. We obtained Ce₂TiO₅ which is isotypic to La₂TiO₅ and crystallizes in the Y₂TiO₅-type (space group Pnma) with a = 10.877(6) Å, b = 3.893(1) Å, c = 11.389(8) Å, Z = 4. Ce₂Ti₂O₇ is isotypic to La₂Ti₂O₇ and crystallizes in the monoclinic Ca₂Nb₂O₇ type (space group P 2₁) with a = 7.776(6) Å, b = 5.515(4) Å, c = 12.999(6) Å, β = 98.36(5), Z = 4. The compound Ce₄Ti₉O₂₄ crystallizes orthorhombic with a = 14.082(4) Å, b = 35.419(8) Å, c = 14.516(4) Å, Z = 16. The new cerium titanate Ce₄Ti₉O₂₄ is isotypic to Nd₄Ti₉O₂₄ (space group Fddd (No. 70)) which represents a novel type of structure.     

[As(V)As(III)O6]: An uncommon anion group in the crystal structure of K2Cu3(As2O6)2

The crystal structure of K₂Cu₃(As₂O₆)₂ was determined from single-crystal X-ray data by a direct method strategy and Fourier summations [a = 10.359(4) Å, B = 5.388(2)Å, C = 11.234(4) Å, β = 110.48(2)°; space group C2/m; Z = 2; R_w = 0.025 for 1199 reflections up to sin /λ = 0.81 Å⁻¹]. In detail, the structure consists of As(V)O₄ tetrahedra and As(III)O₃ pyramids linked by a common O corner atom to [As(V)As(III)O₆]⁴⁻ groups with symmetry m. The bridging bonds As(V)---O [1.749(3) Å] and As(III)---O [1.838(2) Å] are definitely longer than the other As(V)---O bonds [mean 1.669 Å] and As(III)---O bonds [1.764(2) Å, 2×]. The angle As(V)---O---As(III) is 123.0(1)°. The Cu atoms are [4 + 2]- and [4 + 1]-, and the K atom is [9]-coordinated to oxygen atoms. The As₂O₆ groups and the Cu coordination polyhedra are linked to sheets parallel to (001). These sheets are connected by the K atoms. Single crystals of K₂Cu₃(As₂O₆)₂ suitable for X-ray work were synthesized under hydrothermal conditions.     

The crystal structure of Hg2FeF5(OH)2 · H2O

The new compound Hg₂FeF₅(OH)₂ · H₂O was prepared by evaporation of an aqueous 40% HF solution containing HgO and FeF₃ in the stoichiometric ratio. The material is orthorhombic, space group Cmmm, with a = 7.505(1) Å, b = 11.823(3) Å, c = 3.941(2)Å, and Z = 2. The crystal structure was determined from single crystal intensity data obtained by means of an automated four-circle diffractometer and refined to the conventional values R = 0.0621 and R_w = 0.0566 for 451 observed reflections. The structure is characterized by infinite straight chains of FeF₆ octahedra sharing trans F atoms in the direction [001]. These chains are linked by rutile-type chains of HgF₄(OH)₂ octahedra also running along [001]. Water molecules are statistically distributed on half of the 4i positions; they are off-centered in the channels parallel to [001] allowing O---H ··· F bonding. The structure is compared to that of HgFeF₅ · 2H₂O and to that of the hexagonal tungsten bronze.     

Ba2(VO2)(PO4)(HPO4)·H2O, a New Barium Vanadium(V) Phosphate Hydrate Containing Trigonal Bipyramidal VO5Groups

The hydrothermal synthesis, single crystal structure, and some physical properties of Ba₂(VO₂)(PO₄)(HPO₄)·H₂O, a new barium vanadium(V) phosphate hydrate, are reported. This phase is built up from one-dimensional chains of unusual VO₅trigonal bipyramids and (H)PO₄tetrahedra, fused together via V–O–P linkages. These anionic chains propagate along the polar [010] direction. 11-Coordinate barium cations and water molecules occupy the interchain regions and link the chains together. Structural data for this phase and other known barium vanadium phosphates are briefly compared. Crystal data: Ba₂(VO₂)(PO₄)(HPO₄)·H₂O,M_r=566.57, monoclinic, space groupP2₁(No. 4),a=5.0772(5) Å,b=8.724(2) Å,c=10.806(1) Å,β=90.795(8)°,V=478.6(1) ų,Z=2,R=2.65%,R_w=2.89% [147 parameters, 1893 observed reflections withI>3σ(I)].     

X-Ray and TEM Studies of CdTeMoO6 and CoTeMoO6: A New Superstructure of Fluorite Type with Cation and Anion Deficiencies (▪CoTeMo)(□2O6)

The crystal structures of two telluromolybdates CdTeMoO₆ and CoTeMoO₆ have been solved ab initio. CdTeMoO₆ crystallizes in a tetragonal cell (space group No. 113, P 2₁m, Z=2) with a=5.2840(1) Å, c=9.0595(2) Å whereas CoTeMoO₆ crystallizes in orthorhombic space group P2₁2₁2 (No. 18) with two formula units in the unit cell of dimensions a=5.2545(1) Å, b=5.0653(1) Å, and c=8.8589(2) Å. The X-ray powder diffraction pattern data were refined by the Rietveld profile technique and led respectively to R_Bragg=0.07 for CdTeMoO₆ and R_Bragg=0.07 for CoTeMoO₆. The crystal structure of CdTeMoO₆ is built up from corner-sharing distorted CdO₄ tetrahedra which build a layer in the a,b plane, while in CoTeMoO₆ cobalt atoms exhibited an octahedral distorted surrounding. Both compounds are simultaneously cation- and anion-deficient 1.1.2 superstructures of fluorite in which the electron lone pairs of tellurium are stereo-chemically active. High-resolution electron microscopy images of CdTeMoO₆ showed well-ordered crystals fragments, but in some crystals defects have also been detected.     

(C6H16N2)Zn3(HPO3)4H2O: a new layered zinc phosphite templated by diprotonated trans-1,4-diaminocyclohexane

Employing trans-1,4-diaminocyclohexane (trans-1,4-DACH) as a template, a new two-dimensional layered zinc phosphite (C₆H₁₆N₂)Zn₃(HPO₃)₄H₂O (1) has been prepared hydrothermally. Single-crystal X-ray diffraction analysis shows that it crystallizes in the monoclinic space group P2₁/n with a=10.458(2) Å, b=14.720(3) Å, c=13.079(3) Å, β=97.93(3)°, V=1994.1(7) ų, Z=4, R₁=0.0349 (I>2σ(I)) and wR₂=0.0605 (all data). The inorganic layer is built up by alternation of ZnO₄ tetrahedra and HPO₃ pseudo pyramids forming a 4.6.8-net. The sheet is featured by a series of capped six-membered rings. The diprotonated trans-1,4-DACH molecules reside in the interlayer region and interact with the inorganic network through H-bonds.     

Three modifications of BaCu(SeO3)2 and the compound SrCu(SeO3)2: Preparation and crystal structure determination

The crystal structures of four hydrothermally synthesized alkaline earth-copper-selenites were determined: BaCu(SeO₃)₂-I [a = 5.247(1), B = 13.353(2), C = 8.981(1) Å, space group Pnm2₁, Z = 4, R_w = 0.024 for 1270 reflections], BaCu(SeO₃)₂-II [a = 5.256(1), B = 13.231(2), C = 8.933(1) Å, β = 90.19(1)°, space group P2₁/c, Z = 4, R_w = 0.046 for 2238 reflections], BaCu(SeO₃)₂-III [a = 8.031(1), B = 5.185(1), C = 15.823(2) Å, β = 90.83(1)°, space group C2/c, Z = 4, R_w = 0.038 for 1866 reflections], and SrCu(SeO₃)₂ [a = 7.929(1), B = 5.132(1), C = 14.997(2) Å, β = 90.53(1)°, space group C2/c, Z = 4, R_w = 0.028 for 1414 reflections; isotypic with BaCu(SeO₃)₂-III].BaCu(SeO₃)₂-I and -II contain Cu(SeO₃)₂ sheets lying parallel to (100) formed by CuO₄ “squares” and selenite groups. These sheets are topologically different: in BaCu(SeO₃)₂-I they are formed by the connection of Cu₂(SeO₃) and Cu₆(SeO₃)₄ rings while in BaCu(SeO₃)₂-II they are formed by Cu₂(SeO₃)₂ and Cu₆(SeO₃)₆ rings. The Cu(SeO₃)₂ sheets are rugged in BaCu(SeO₃)₂-I and they are slightly waved in BaCu(SeO₃)₂-II. In both compounds they are connected to each other by a fifth Cu---O bond and by the Ba atoms. In BaCu(SeO₃)₂-III and in its isotypic Sr analog the CuO₄ “squares” and the selenite groups form parallel chains [010], which are connected by the alkaline earth atoms.     

The Glaserite-like Structure of Double Sodium and Iron Phosphate Na3Fe(PO4)2

The double sodium and iron phosphate Na₃Fe(PO₄)₂ was synthesized and studied by the XRD method, the second harmonic generation technique, and Mössbauer and IR spectroscopy. The compound crystallizes into a monoclinic system (space group C2/c) with unit cell parameters a=9.0736(2) Å, b=5.0344(1) Å, c=13.8732(3) Å, β=91.435(2)° and is found to be related to the K₃Na(SO₄)₂ structure type. The crystal structure was determined by Rietveld analysis (R_wp=5.86, R_I=2.03). Iron cations occupy the M (Na) position while sodium cations occupy the X (K) and Y (K) positions of the glaserite-like structure. Mössbauer spectroscopy shows the presence of high-spin Fe³⁺ in octahedral coordination.     

The thallium tungstate Tl2W4O13: A tunnel structure related to the hexagonal tungsten bronze

The crystal structure of thallium tungstate Tl₂W₄O₁₃ (a = 7.327Å; b = 37.864 Å; c = 3.840 Å; space group Pmab) has been resolved by three-dimensional single-crystal X-ray analysis. The average structure was resolved by standard Patterson and Fourier techniques and refined by full-matrix least squares to final agreement indices R = 0.087 and R_w = 0.100. Superstructure reflections referred to a supercell (a, b, 2c; space group Pcab) led to a framework model which is described. The structure consists of corner-sharing chains of WO₆ octahedra parallel to a and c axes. Hexagonal and pentagonal tunnels, bound by these chains, are filled by thallium atoms. The atomic arrangement is closely related to the hexagonal bronze structure. The tungstate Tl₂W₄O₁₃ can thus be considered as a member of a series of phases (TlB₃X₉)_n · Tl₆B₁₀X₃₄ (X = O, F) involving hexagonal tungsten bronze ribbons.     

The Crystal Structures of the Strontium Gallates Sr10Ga6O19 and Sr3Ga2O6

The crystal structures of Sr₁₀Ga₆O₁₉ and Sr₃Ga₂O₆ have been characterized using X-ray diffraction techniques. In the case of Sr₁₀Ga₆O₁₉, the structure was determined from a single crystal diffraction data set collected at room conditions and refined to a final R index of 0.061 for 3471 observed reflections (I>2 σ(I)). The compound is monoclinic with space group C12/c1 (a=34.973(4) Å, b=7.934(1) Å, c=15.943(2) Å, β=103.55(1)°, V=4300.7(6) ų, Z=8, D_calc=4.94 g/cm³, μ(MoKα)=32.04 mm⁻¹) and can be classified as an oligogallate. It is the first example of an inorganic compound where six [TO₄]-tetrahedra of only one chemical species occupying the tetrahedral centres are linked via bridging oxygen atoms to form [T₆O₁₉] groups. The hexamers are not linear, but highly puckered. Eleven symmetrically different Sr cations located in planes parallel (100) crosslink between the oligo-groups. They are coordinated by six to eight oxygen ligands. The structure of Sr₃Ga₂O₆ has been refined from powder diffraction data using the Rietveld method (space group Pa , a=16.1049(1), V=4177.1(1) ų, Z=24, D_calc=4.75 g/cm³). The compound is isostructural with tricalcium aluminate and contains highly puckered, six-membered [Ga₆O₁₈]¹⁸⁻ rings. The rings are linked by strontium cations having six to nine nearest oxygen neighbors.     

Structure and properties of triclinic Ni0.85Mo6Te8

The structure of Ni_0.85Mo₆Te₈ was refined from single-crystal X-ray diffraction data at room temperature. It is triclinic, space group

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; 1619 reflections, 75 refined parameters, R = 0.031. The Mo atoms form distorted octahedral clusters (2.69 Å ≤ d_intra[Mo---Mo] ≤ 2.81 Å; 3.58 Å < d_inter[Mo---Mo]). The Ni atoms are disordered (site occupancy: 0.423(7); d[Ni---Ni] = 2.586(6) Å), and interact strongly with one Mo₆ cluster (d[Ni---Mo] = 2.603(3) and 2.958(3) Å), and weakly with another (d[Ni---Mo] = 2.985(3) Å). The structure transforms at 1057(5) K into a rhombohedral modification (a_hex = 10.457(2) Å, c_hex = 11.866(3) Å at 1073 K). Measurements on powders suggest metallic conductivity (5.1 × 10⁻⁴ Ω-cm at 293 K) and weakly temperature-dependent paramagnetism (110 × 10⁻⁶ emu/g at 100 K).     

Synthesis and characterization of [Zn(2,2′-bipy)]2(H2PO3)4: A neutral zinc phosphite cluster containing ZnO3N2 and H2PO3 units

The hydrothermal synthesis, crystal structure and some properties of a zinc phosphite with a neutral cluster, [Zn(2,2′-bipy)]₂(H₂PO₃)₄, are reported. This compound crystallizes in the triclinic system of space group P-1 (No. 2), a=8.3067(5) Å, b=8.9545(4) Å, c=10.0893(6) Å, α=95.448(2)°, β=99.7530(10)°, γ=103.461(2)°, V=712.23(7) ų, Z=1. The cluster consists of 4-membered rings formed by alternating ZnO₃N₂ square pyramids and H₂PO₃ pseudo pyramids, with two “hanging” H₂PO₃ groups attached to each of the Zn centers. The clusters are linked together by extensive multipoint hydrogen bonding involving the phosphite units to form a sheet-like structure. This compound represents the first example of zinc phosphite with P---OH bonds. An intense photoluminescence was observed from this compound upon photoexcitation at 388 nm.     

Phase Transition in Cs2KMnF6: Crystal Structures of Low- and High-Temperature Modifications

Crystalline Cs₂KMnF₆, when prepared below 500°C, adopts a tetragonal elpasolite structure type. Differential scanning calorimetric investigations indicated that Cs₂KMnF₆ undergoes a phase transition from the low-temperature tetragonal phase (LT) to a high-temperature phase (HT) at about 530°C. Single crystals of the new HT phase could be obtained by annealing a crystalline LT specimen at 600°C followed by rapid quenching to room temperature. In the present study the structures of both phases have been studied by single-crystal X-ray diffraction techniques. The LT phase has the tetragonal space group symmetry I4/mmm, with unit-cell parameters a=6.319(1) (a· =8.936) and c=9.257(2) Å, and Z=2. The HT phase has the cubic symmetry Fm3m, with the cell parameter a=9.067 Å and Z=4. Structural models of the LT and HT phases have been refined vs collected single-crystal X-ray reflection data to R values of 0.034 and 0.022, respectively. The uneven Mn–F bond distance distribution in the LT form, four bonds of 1.860(6) two of 2.034(9) Å, are typical for an octahedrally coordinated high-spin Mn³⁺ ion affected by Jahn–Teller effects. Due to symmetry constraints, all six octahedral Mn–F bonds in the HT form are equal to 1.931(5) Å. However, the mean square atomic displacement parameters of the fluorine atoms increases significantly from about 0.022 Ų for the LT phase to 0.042 Ų for the HT phase. The increased displacement parameters indicate that the phase transition from the LT to the HT form is associated with a directional disorder of the Jahn–Teller distortions around the Mn³⁺ ions.     

Li3−xTi2(PO4)3 (0 ≤ x ≤ 1): A new mixed valent titanium(III/IV) phosphate with a NASICON-type structure

A new NASICON-related structure of lithium titanium phosphate Li_2.72Ti₂(PO₄)₃ has been determined. This compound crystallizes in an orthorhombic system, Pbcn, with a = 12.064 (3) Å, b = 8.663 (3) Å, c = 8.711 (4) Å, V = 910.4 (8) ų, and Z = 4. The single crystal structure of this novel mixed valent titanium(III/IV) phosphate reveals one titanium atom per asymmetric unit. Two lithium sites are characterized by a pair of distorted polyhedra, Li(1)O₄ and Li(2)O₅, which share a common edge resulting in a short Li(1) … Li(2) distance, i.e., 2.29 (5) Å. Magnetic susceptibility and microprobe analysis confirmed the structural composition. The room temperature ionic conductivity is comparable with that of the known Li_1+xTi^IV_2−xIn^III_x(PO₄)₃, which suggests possible fast ionic conductivity.     

An oxygen deficient fluorite with a tunnel structure: Bi8La10O27

A new lanthanum bismuth oxide, Bi₈La₁₀O₂₇, has been synthesized. It crystallizes in the Immm space group with the following parameters: a = 12.079 (2) Å, b = 16.348 (4) Å, c = 4.0988 (5) Å. Its structure was determined from powder X-ray and neutron diffraction data. It can be described as an oxygen deficient fluorite superstructure (a ≈ 3a_F/√2, b ≈ 3a_F, c ≈ a_F/√2) in which bismuth and lanthanum, as well as oxygen vacancies, are ordered. The structure consists of fully occupied (110) or lanthanum planes (La) which alternate with mixed planes and fully occupied oxygen planes (A) which alternate with two sorts of oxygen deficient (110) or planes (B and C) according to the sequence . The anionic distribution determines tunnels where the bismuth ions are located, forming diamond-shaped based tunnels. The coordination of bismuth and lanthanum is discussed. The high thermal factor of some oxygen atoms suggests that this oxide exhibits ionic conductivity.