NaFe(TeO3)2

The hydro­thermally prepared title compound, sodium iron(III) bis­[trioxotellurate(IV)], is isotypic with its GaIII analogue and consists of corrugated layers with an overall composition of [FeTe2O6]− together with Na+ cations. The layers extend parallel to (001) and are made up of [Fe2O10] edge-shared octa­hedral dimers and TeO3 trigonal pyramids sharing vertices. The Na+ cations are located in the cavities of this arrangement and link adjacent [FeTe2O6]− layers via distorted [NaO8] polyhedra

Crystal structure of the thortveitite-related M phase, (MnxZn1-x)2V2O7 (0.75 < x < 0.913): a combined synchrotron powder and single-crystal X-ray study.

The determination of the crystal structure of the M phase, (MnxZn1-x)2V2O7 (0.75 < x < 0.913), in the pseudobinary Mn2V2O7-Zn2V2O7 system for x ≃ 0.8 shows that the previously published triclinic unit-cell parameters for this thortveitite-related phase do not describe a true lattice for this phase. Instead, single-crystal X-ray data and Rietveld refinement of synchrotron X-ray powder data show that the M phase has a different triclinic structure in the space group P-1 with Z = 2. As prior work has suggested, the crystal structure can be described as a distorted version of the thortveitite crystal structure of β-Mn2V2O7. A twofold superstructure in diffraction patterns of crystals of the M phase used for single-crystal X-ray diffraction work arises from twinning by reticular pseudomerohedry. This superstructure can be described as a commensurate modulation of a pseudo-monoclinic basis structure closely related to the crystal structure of β-Mn2V2O7. In comparison with the distortions introduced when β-Mn2V2O7 transforms at low temperature to α-Mn2V2O7, the distortions which give rise to the M phase from the β-Mn2V2O7 prototype are noticeably less pronounced.Funding for this research was provided by: Royal Society (joint international exchange programme award to Anjan Sil); British Council, New Delhi (UKIERI project No. SA07-0052 to Kevin Knowles, Anjan Sil)

Crystal Structure and Characterisation of Mercury(II) Dichromate(VI)

Dark-red single crystals of HgCr2O7 were grown by reacting HgO and CrO3 in excess at 200°C for four days. The crystal structure (space group P32, Z = 3, a = 7.2389(10), c = 9.461(2) A, 1363 structure factors, 57 parameters, R[F2>2σ(F2)] = 0.0369, wR(F2 all) = 0.0693) was determined from a crystal twinned by merohedry according to (110). It consists of nearly linear HgO2 units (${\bar {d}}$(Hg–O) = 2.02 A) and dichromate units that are linked into infinite chains ‘O3Cr–O–CrO3–Hg–O3Cr–O–CrO3’ running parallel to the c-axis. Six additional Hg–O contacts between 2.73 and 2.96 A stabilise the structural arrangement. The dichromate anion exhibits a staggered conformation with a bent Cr–O–Cr bridging angle of 140.7(6)°. Upon heating above 300°C, HgCr2O7 decomposes in a two-step mechanism to Cr2O3. The title compound was additionally characterised by vibrational spectroscopy.Centro de Química Inorgánic

K3Al2As3O12

Single crystals of K3Al2As3O12, tripotassium dialuminotriarsenate(V), were obtained unintentionally by the reaction of KAsO3 with a corundum crucible at 973 K. The asymmetric unit contains three K, two Al, three As and 12 O atoms. The structure of the title compound is isotypic with those of other K3 M′2 X 3O12 (M′ = Al, Ga; X = P, As) structures and is made up of a three-dimensional network of corner-sharing [AlO4] and [AsO4] tetra­hedra. The three K+ cations are located in channels running along the [100], [001], [101] and [10] directions, exhibiting different coordination numbers of 9, 8 and 6, respectively. All corresponding [KOx] polyhedra are considerably distorted

Pb3Te2O6Br2

Single crystals of the title compound, trilead(II) bis­[tellurate(IV)] dibromide, have been grown under hydro­thermal conditions. The structure is isotypic with that of the chloride analogue, Pb3Te2O6Cl2, and consists of three Pb, two Te, two Br and four O atoms in the asymmetric unit. Except for two of the O atoms, all atoms are located on mirror planes. The Pb3Te2O6Br2 structure can be described as being built up from ∞ 2[Pb3Te2O6]2+ layers extending parallel to (20) and Br− anions between the layers. Cohesion of the structure is accomplished through Pb—Br contacts of two of the three lead atoms, leading to highly asymmetric coordination polyhedra. The lone-pair electrons of both TeIV and PbII atoms are stereochemically active and point towards the anionic halide layers

Crystal Structure and Characterisation of Mercury(II) Dichromate(VI)

Dark-red single crystals of HgCr2O7 were grown by reacting HgO and CrO3 in excess at 200°C for four days. The crystal structure (space group P32, Z = 3, a = 7.2389(10), c = 9.461(2) A, 1363 structure factors, 57 parameters, R[F2>2σ(F2)] = 0.0369, wR(F2 all) = 0.0693) was determined from a crystal twinned by merohedry according to (110). It consists of nearly linear HgO2 units (${\bar {d}}$(Hg–O) = 2.02 A) and dichromate units that are linked into infinite chains ‘O3Cr–O–CrO3–Hg–O3Cr–O–CrO3’ running parallel to the c-axis. Six additional Hg–O contacts between 2.73 and 2.96 A stabilise the structural arrangement. The dichromate anion exhibits a staggered conformation with a bent Cr–O–Cr bridging angle of 140.7(6)°. Upon heating above 300°C, HgCr2O7 decomposes in a two-step mechanism to Cr2O3. The title compound was additionally characterised by vibrational spectroscopy.Centro de Química Inorgánic

Ammonium bis(salicylaldehyde thiosemicarbazonato)ferrate(III), a supramolecular material containing low-spin FeIII

The synthesis and crystal structure (100 K) of the title com­pound, ammonium bis­[salicyl­aldehyde thio­semi­car­ba­zon­ato(2−)-κ3O,N1,S]iron(III), NH4[Fe(C8H7N3OS)2], is reported. The asymmetric unit consists of an octa­hedral [FeIII(thsa)2]− fragment, where thsa2− is salicyl­aldehyde thio­semi­car­ba­zon­ate(2−), and an NH4+ cation. Each thsa2− ligand binds via the thiol­ate S, the imine N and the phenolate O donor atoms, resulting in an FeIIIS2N2O2 chromophore. The ligands are orientated in two perpendicular planes, with the O and S atoms in cis and the N atoms in trans positions. The FeIII ion is in the low-spin state at 100 K. The crystal structure belongs to a category I order–disorder (OD) family. It is a polytype of a maximum degree of order (MDO). Fragments of the second MDO polytype lead to systematic twinning by pseudomerohedry

Anisotropic Physical Properties of the Kondo Semimetal CeCu1.11_{1.11}As2_2

The recently proposed novel materials class called Weyl-Kondo semimetal (WKSM) is a time reversal invariant but inversion symmetry broken Kondo semimetal in which Weyl nodes are pushed to the Fermi level by the Kondo interaction. Here we explore whether CeCu$_{1+x}$As$_2$ may be a new WKSM candidate. We report on its single-crystal growth, structure determination and physical properties investigation. Previously published studies on polycrystalline samples suggest that it is indeed a Kondo semimetal, which is confirmed by our investigations on single crystals. X-ray diffraction reveals that CeCu$_{1+x}$As$_2$ crystallizes in a tetragonal centrosymmetric structure, although the inversion symmetry could still be broken locally due to partially occupied Cu sites. Chemical analysis results in an average occupation $x$ = 0.11(1). The electrical resistivity increases logarithmically with decreasing temperature, and saturates below 10 K. A Kondo temperature $T_{\mathrm{K}}$ $\approx$ 4 K is extracted from entropy, estimated from the specific heat measurements. From Hall effect experiments, a charge carrier density of $8.8 \times 10^{20}$ cm$^{-3}$ is extracted, a value characteristic of a semimetal. The magnetization shows pronounced anisotropy, with no evidence of magnetic ordering down to 0.4 K. We thus classify CeCu$_{1.11}$As$_2$ as a tetragonal Kondo semimetal with anisotropic magnetic properties, with a possibly broken inversion symmetry, thus fulfilling the necessary conditions for a WKSM state.Comment: 6 pages, 4 figures, Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019

The dehydration of SrTeO3(H2O) - a topotactic reaction for preparation of the new metastable strontium oxotellurate(IV) phase e-SrTeO3

Microcrystalline single-phase strontium oxotellurate(IV) monohydrate, SrTeO3 (H2O), was obtained by microwave-assisted hydrothermal synthesis under alkaline conditions at 180 ◦C for 30 min. A temperature of 220 ◦C and longer reaction times led to single crystal growth of this material. The crystal structure of SrTeO3 (H2O) was determined from single crystal X-ray diffraction data: P21/c, Z = 4, a = 7.7669(5), b = 7.1739(4), c = 8.3311(5)A˚ , b = 107.210(1)◦, V = 443.42(5)A˚ 3 , 1403 structure factors, 63 parameters, R[F2&gt;2s(F2 )] = 0.0208, wR(F2 all) = 0.0516, S = 1.031. SrTeO3 (H2O) is isotypic with the homologous BaTeO3 (H2O) and is characterised by a layered assembly parallel to (100) of edge-sharing [SrO6 (H2O)] polyhedra capped on each side of the layer by trigonal-prismatic [TeO3 ] units. The cohesion of the structure is accomplished by moderate O–H ◊ ◊ ◊ O hydrogen bonding interactions between donor water molecules and acceptor O atoms of adjacent layers. In a topochemical reaction, SrTeO3 (H2O) condensates above 150 ◦C to the metastable phase e-SrTeO3 and transforms upon further heating to d-SrTeO3 . The crystal structure of e-SrTeO3 , the fifth known polymorph of this composition, was determined from combined electron microscopy and laboratory X-ray powder diffraction studies: P21/c, Z = 4, a = 6.7759(1), b = 7.2188(1), c = 8.6773(2)A˚ , b = 126.4980(7)◦, V = 341.20(18)A˚ 3 , RFobs = 0.0166, RBobs = 0.0318, Rwp = 0.0733, Goof = 1.38. The structure of e-SrTeO3 shows the same basic set-up as SrTeO3 (H2O), but the layered arrangement of the hydrous phase transforms into a framework structure after elimination of water. The structural studies of SrTeO3 (H2O) and e-SrTeO3 are complemented by thermal analysis and vibrational spectroscopic measurements.Centro de Química Inorgánic