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Understanding the properties of transition metal materials requires consideration of the competition between the various types of electrons that comprise the system, whether they be delocalized and metallic, localized and magnetic, or localized and bonded. Here we report the refined crystal structure determination and physical properties of the two-dimensional layered compound TaOCl 2. Within each layer we find a strong in-plane dimerization of Ta atoms perpendicular to the Ta-O-Ta chains, with significant disorder in the positioning of dimers in adjacent layers, suggesting that the free electron of each Ta localizes in Ta-Ta bonds. This is supported by resistivity measurements (ρ 300K = 4.4*108 Ω-cm) as well as featureless, temperature-independent magnetic susceptibility up to T = 750 K. Analysis of the phonon contribution to specific heat shows the presence of a localized Einstein mode with T E = 175 K, attributed to the localized vibrations of the Ta-Ta dimers. Density functional theory calculations show that the magnitude of the Ta displacements (0.24 Å) has a dramatic effect on the electronic structure, changing from a metal with a bandwidth of 3.2 eV to an insulator with a flat band just below E F. Our results show how direct exchange interactions between Ta atoms that are relatively far from each other can still play a central role in the behavior of 5d transition metal compounds, taking advantage of the extended 5d atomic orbitals, and produce localized dimers with a bond distance of approximately 2.84 Å. Illustrating the discovery of and modeling disorder in the crystal structure of TaOCl 2. [Display omitted] • In-plane disorder leading to Ta-Ta dimerization discovered in crystal structure. • Dimerization significantly affects physical properties. • Significant electrical resistance observed, at odds with predicted electronic band structure of undistorted crystal structure. • Significant potential for tuning of crystal structure and properties. [ABSTRACT FROM AUTHOR]

A novel mixed-anion oxychloride, KBi(SeO 4)(IO 3)Cl, has been hydrothermally synthesized and structurally characterized. The compound crystallizes in the monoclinic space group of P 2 1 /c with cell parameters of a = 7.8802(2) Å; b = 10.8088(2) Å, c = 10.1364(2) Å, β = 112.849(1)°, V = 795.62(3) Å3, and Z = 4. KBi(SeO 4)(IO 3)Cl exhibits a three-dimensional tunnel framework that is composed of three types of atomic groups, i.e., tetrahedral SeO 4 , trigonal pyramidal IO 3 , and polyhedral BiO 6 Cl. Both IO 3 pyramid and BiO 6 Cl polyhedron are in strongly acentric coordination due to the influence of I5+ and Bi3+ lone electron pairs. The measurement of UV–vis–NIR spectra for powder KBi(SeO 4)(IO 3)Cl indicates that the material is a wide band gap semiconductor with E g = 3.9 eV. Theoretical analysis shows that the electron transition from Bi 6p to O 2p states in the BiO 6 Cl unit dominates the optical absorption edge. Thermal stability and IR spectrum were also analyzed for the material. A novel oxychloride KBi(SeO 4)(IO 3)Cl was hydrothermally synthesized and structurally determined for the first time. The compound shows a 3D tunnel framework composed of three functional units SeO 4 tetrahedron, IO 3 trigonal pyramid, and BiO 6 Cl polyhedron. [Display omitted] • A novel mixed-anion oxychloride KBi(SeO 4)(IO 3)Cl was hydrothermally synthesized and structurally determined. • KBi(SeO 4)(IO 3)Cl shows a 3D tunnel framework composed of three functional units. • KBi(SeO 4)(IO 3)Cl is a wide band gap semiconductor with E g = 3.9 eV. [ABSTRACT FROM AUTHOR]

A new mayenite-type strontium oxy-chloride, Sr 12 Al 3.44 Fe 8.16 Ge 2.38 O 32 Cl 4.34 , was grown from a SrCl 2 flux at 1000 ​°C. The compound crystallizes in the complex three-dimensional chloromayenite structure type, a rare calcium aluminum oxide mineral of cubic symmetry, exhibiting nanocages that contain Sr and Cl ions. The lattice framework is composed of corner-sharing, three-component Al/Fe/Ge site-mixed tetrahedra. The compound crystallizes in the cubic space group I -43 d with lattice parameter a ​= ​12.6126(3) Å. [Display omitted] • Single crystals of Sr 12 Al 3.44 Fe 8.16 Ge 2.38 O 32 Cl 4.34 (SAFGOC) were grown out of molten SrCl 2 flux. • The crystal structure of the compound was solved using single crystal X-ray diffraction. • SAFGOC crystallizes in mayenite structure type and exhibits three-component site mixing. [ABSTRACT FROM AUTHOR]

Abstract: A new oxychloride Pb5Fe3TiO11Cl has been synthesized using the solid state method. Its crystal and magnetic structure was investigated in the 1.5–550K temperature range using electron diffraction, high angle annular dark field scanning transmission electron microscopy, atomic resolution energy dispersive X-ray spectroscopy, neutron and X-ray powder diffraction. At room temperature Pb5Fe3TiO11Cl crystallizes in the P4/mmm space group with the unit cell parameters a=3.91803(3)Å and c=19.3345(2)Å. Pb5Fe3TiO11Cl is a new n=4 member of the oxychloride perovskite-based homologous series A n+1 B n O3n−1Cl. The structure is built of truncated Pb3Fe3TiO11 quadruple perovskite blocks separated by CsCl-type Pb2Cl slabs. The perovskite blocks consist of two layers of (Fe,Ti)O6 octahedra sandwiched between two layers of (Fe,Ti)O5 square pyramids. The Ti4+ cations are preferentially located in the octahedral layers, however, the presence of a noticeable amount of Ti4+ in a five-fold coordination environment has been undoubtedly proven using neutron powder diffraction and atomic resolution compositional mapping. Pb5Fe3TiO11Cl is antiferromagnetically ordered below 450(10)K. The ordered Fe magnetic moments at 1.5K are 4.06(4)μB and 3.86(5)μB on the octahedral and square-pyramidal sites, respectively. [Copyright &y& Elsevier]

Abstract: The oxidation of HCl to Cl2 (Deacon process) was studied over RuO2-based catalysts in bulk and supported forms. RuO2 (7wt.%) was incorporated onto different TiO2 carriers (rutile, anatase, and P25) by deposition–precipitation of Ru(OH)2 followed by calcination. RuO2/TiO2-rutile exhibits the highest activity at ambient pressure in a continuous flow fixed-bed reactor. Insights into the mechanism of this experimentally demanding reaction on RuO2 and the influence of the TiO2-rutile carrier were gained by studies in the Temporal Analysis of Products (TAP) reactor at 623K. HCl multipulsing in the absence of O2 leads to chlorination of the catalysts with no detectable gas-phase Cl2 production. The chlorine uptake of RuO2 amounts to 0.16mmolCl , which enables to estimate that ca. 75% of the total surface Ru atoms (coordinatively unsaturated and bridge sites) are chlorinated, forming a RuO2− x Cl x oxychloride. RuO2 is also chlorinated by Cl2, but to a lesser extent compared to HCl. The chlorine uptake of fresh RuO2/TiO2-rutile per gram of sample was four times higher than that of fresh RuO2, namely due to chlorination of the high surface area carrier. Upon equilibration at ambient pressure under Deacon conditions, the TAP-derived chlorine uptake in the supported catalyst experienced a 6-fold decrease with respect to the fresh sample due to permanent chlorination. Pulsing of a mixture of O2 and HCl over the catalysts revealed that both gas-phase Cl2 evolution and H2O desorption are impeded processes. Pump–probe experiments of O2 and HCl evidenced the tight dependence of the net Cl2 production on both the oxygen and chlorine coverage. In addition, a limited contribution of lattice surface species could be detected by the production of small amounts of Cl2 at very low coverages. The equilibration procedure (ambient or TAP conditions) influences the reaction mechanism and the net Cl2 production, giving account of the reaction complexity due to the highly dynamic state of the catalyst surface. The Deacon process on RuO2− x Cl x -based catalysts can be mostly described by a Langmuir–Hinshelwood scheme with a minor 2D Mars–van Krevelen contribution. [Copyright &y& Elsevier]

Abstract: Solid state solutions of Ca4Fe3− x Mn x O8− δ Cl2 (0.92≤x≤1.79 (δ∼0.1) single crystals were synthesized in CaCl2-flux in air. The structure, determined by single-crystal X-ray diffraction, is related to the n=3 Ruddlesden–Popper phase in space group I4/mmm with strong deviations from the ideal structure. Mn and Fe are disordered over two transition metal sites. Due to the positional disordering of the equatorial oxygen atoms in the MO6 octahedra in Ca4Fe3− x Mn x O8− δ Cl2 both tilting (∼9°) along the c-axis and rotation (∼10.5°) within the ab-plane are observed. All the Fe ions are trivalent, as confirmed by 57Fe Mössbauer spectroscopy and X-ray absorption near edge spectroscopy (XAS), while the formal valence state of Mn varies from very close to 4+ in the x=0.92 to mix-valent 3+/4+ in the x=1.79 member, as indicated by XAS. Magnetic investigations evidence short-range antiferromagnetic ordering already at room temperature and spin-glass behavior at low temperature due to the structural disordering of Mn/Fe. [Copyright &y& Elsevier]

Abstract: A new bismuth tellurium oxychloride was obtained by reaction of BiOCl and TeO2 in air. According to energy dispersive X-ray spectroscopy and neutron powder diffraction refinement the composition of the substance was determined as Bi0.87Te2O4.9Cl0.87. The new compound crystallizes in the trigonal system space group R 3¯ (#148), Z=6, a=4.10793(4), c=31.1273(4)Å, χ 2=3.20, wR p=0.0369. Bi0.87Te2O4.9Cl0.87 has a new type of layered structure constructed by Bi–Te–O layers separated by chloride ions. The Te atoms in Bi0.87Te2O4.9Cl0.87 show an unusual umbrella-like environment. A comparison with known related structures has been made. [Copyright &y& Elsevier]

Abstract: The thermogravimetric behavior of HfCl4 powders with different hydration states has been compared. Strongly hydrated powders consist of HfOCl2·nH2O with . Partially hydrated powders consist of particles with a HfCl4 core and a hydrated outerlayer of HfOCl2·nH2O with n in the range of 0–8. Hydrated powders decomposed at temperature lower than 200°C whereas the decomposition of partially hydrated powders was completed at a temperature of around 450°C. The observed differences in decomposition temperature is related to the structure of HfOCl2·nH2O, which is different if n is higher or smaller than 4 and leads to intermediate compounds, which decompose at different temperatures. [Copyright &y& Elsevier]

Crystals of Ba5Fe5−xPtxClO13 and Ba5Co5−yPtyClO13 were prepared for x=1.31, 1.51, 1.57, 1.59 and y=0, 0.97 and 1.08 in a BaCl2 flux and investigated by X-ray diffraction methods. These compounds adopt a 10H perovskite structure built from the stacking of BaO3 and BaOCl layers in the sequence (BaO3)4(BaOCl) with space group P63/mmc. The cation sites within the trimeric unit of face-sharing octahedra are occupied by Co or Fe and Pt ions, while the tetrahedral sites formed between BaO3 and BaOCl layers are only occupied by Fe or Co. Moreover, oxygen stoichiometry indicates an average oxidation state for Co and Fe higher than +III, indicating the stabilization of Co4+ and Fe4+. [Copyright &y& Elsevier]