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A general structure model for Bi-Se phases using a superspace formalism

Solid-state synthesis in the Bi-Se system produced both commensurate and incommensurate phases of compositions ranging from Bi2Se3 to Bi4Se3, all crystallising in rhombohedral or trigonal layer structures. The a parameters are very similar for all phases but the c parameters vary irregularly between 10 and 100 Å. A general model for all these phases was developed, using single crystal X-ray diffra

Synthesis of structurally controlled nanocarbons - In particular the nanobarrel carbon

Nanoporous carbons have been prepared through a selective etching reaction, performed by halogenisation of aluminum carbide. The structures obtained can be controlled by varying the chlorination temperature. The unique set of nanocarbons obtained include nanoporous amorphous structures, the nanobarrel structure and a nanographitic structure as chlorination temperatures were increased from 400 °C t

Effects from hydrogen bonds on water structure in (H3O)2[Mo6 Cl8X6]·yH2O X = Cl (y = 7), Br (y = 6), or I (y = 6)

The compounds (a) (H3O)2[Mo6Cl8 Cl6]·7H2O, (b) (H3O)2[Mo6 Cl8Br6]·6H2O and (c) (H3O)2[Mo6 Cl8I6].6H2O were synthesized from MoCl2 and the corresponding halide acid. The structures were determined by X-ray diffraction and refined in the monoclinic space groups, (a) C2/c and for (b) and (c) P21/a. The cell parameters were for (a), a = 17.3607(2), b = 9.1351(7), c = 18.6300(2) Å and β = 98.13(1)°, (b

Preparation and double-helix icosahedra structure of δ-Co2Zn15

The first known example of a regular face-sharing icosahedra helix is presented in the novel crystal structure of δCo2Zn15, solved and refined from single-crystal X-ray and neutron powder diffraction data. The compound δCo2Zn15 is also the first example of an intermetallic compound crystallizing in the acentric hexagonal space group P62. The parameters from the single crystal refinement are a = 11

Structure of Dy13Zn57 a binary quasicrystal approximant

The title compound Dy13Zn57, crystallizes in the orthorhombic space group Pnma (No. 62) with the cell parameters a = 14.060(5), b = 14.260(5) and c = 24.700(3) Å. The structure has formerly been described as Dy13Zn58 with the hexagonal type structure of Gd13Zn58. Single-crystal X-ray diffraction measurements however, show extra reflections breaking the C-centering of the corresponding orthorhombic

The structure of Nb5O12F

The title compound was synthesized according to Andersson Acta Chem. Scand. 18 (1964) 2233. The structure is an incommensurately modulated variation of the UO3 structure, in a (3 + 1)-dimensional super space description isostructural to the composite phases (1 - x)Ta2O5•xWO3 Acta Crystallogr., Sect. B 52 (1996) 223 and Acta Crystallogr., Sect. B 51 (1995) 709. The compound crystallizes in the orth

Superlattice formation in the lithiated vanadium oxide phases Li0.67V6O13 and LiV6O13

Two new lithiated phases of V6O13 were formed by carefully tuning the temperature of electrochemical lithiation in a 'coffee-bag' type Li-ion battery at 2.78 V versus Li/Li+. These were studied by single-crystal X-ray diffraction. A phase with the composition Li2/3V6O13 was obtained at 308 K with a unit cell three times the volume of the original V6O13 cell. A single crystal discharged at ambient

Anomalous vibrational dynamics in the Mg2Zn11 phase

We present a combined experimental and theoretical study of the structure and the lattice dynamics in the complex metallic alloy Mg2Zn 11, by means of neutron and x-ray scattering, as well as ab initio and empirical potential calculations. Mg2Zn11 can be seen as an intermediate step in structural complexity between the simple Laves-phase MgZn2 on one side, and the complex 1/1 approximants and quas

Structure of Ca13Cd76 : A novel approximant to the MCd5.7 Quasicrystals (M = Ca, Yb)

The closest cubic approximant to the MCd5.7 (M = Ca, Yb) quasicrystals known so far, namely Ca13Cd76, was obtained by high-temperature reaction of the elements. It exhibits a new type of structure for intermetallic compounds with an unprecedented arrangement of triacontahedral clusters (see structure), which could prove useful in modeling the structures of the MCd5.7 quasicrystals.

Incommensurately modulated Nowotny chimney-ladder phases : Cr1-xMoxGe∼1.75 with x = 0.65 and 0.84

The crystal structures of two new ternary, incommensurately modulated phases in the Cr/Mo/Ge system, Cr1-xMoxGe∼1.75 with x = 0.65 and 0.84, have been refined using the same composite approach as for the earlier reported compounds, (Mo/Rh)11Ge18 and (Mo/Rh)13Ge22, from the Mo/Rh/Ge system. The composite model consists of a rather stable diamond-like transition metal substructure and a helical main

Computer modeling and description of nonstoichiometric apatites Cd5-η/2(VO4)3I1-η and Cd5-η/2(PO4)3Br1-η as modified chimney-ladder structures with ladder-ladder and chimney-ladder coupling

Diffraction patterns from apatite-structure compounds Cd5-η/2(TO4)3X1-η with T=P, V and X=Br, I show sheets of diffuse scattering normal to c* at incommensurate l=q (q=1.63 for Cd-V-I apatite and q=1.78 for Cd-P-Br apatite), because the c repeat of the average unit cell is shorter than two X diameters. The equilibrium X..X spacing along c defines the incommensurate periodicity c/q and stoichiometr

Gallium and indium under high pressure

A study was carried out to explore the structural competition between the high symmetry fcc and low symmetry bct structure for the IIIA metals Al, Ga, and In. It was found that the competition originates from electronic properties. As a result, the high pressure behavior of the metals appears reversed to the corresponding-states rule.

Single crystsl refinement of the incommensurately modulated Mn0.55Ta0.45O1.7, an oxygen deficient fluorite type compound

A structural investigation of the incommensurately ordered compound Mn0.55Ta0.45O1.7 has been carried out, using single-crystal X-ray diffraction data. The basic structure is related to the fluorite type with a monoclinic distortion. Electron diffraction (ED) patterns for various crystal orientations were used for determination of unit cell, incommensurate modulation vector and superspace group. T

Reassessing the compound CeCd6 : the structure of Ce6Cd37

The crystal structure of the phase Ce6Cd37 was determined by single-crystal X-ray diffraction. It is closely related to, and indeed probably identical to, the previously reported compound CeCd6. The compound crystallizes in the centrosymmetric space group Pn3̄ with the unit cell axis 15.808(2) angstrom. The structure may be described by successive shells centered around the origin and the position

On the question of commensurability - The Nowotny chimney-ladder structures revisited

A composite approach was used for the structure solution and refinement of two new Nowotny chimney-ladder phases, (Mo/Rh)11Ge18 and (Mo/Rh)13Ge22, found during investigations in the Mo/Rh/Ge system. The descriptions of the phases with conventional models (in I4̄2d (No. 122) with a = 5.885(2) Å, c = 52.62(2) Å for (Mo/Rh)11Ge18 and a = 5.922(1) Å, c = 62.88(4) Å for (Mo/Rh)13Ge22) led to high numbe

Incommensurately modulated cadmium apatites

Two cadmium apatites, Cd5(PO4)3Br and Cd5(VO4)3I, earlier reported to be halogenide deficient, were prime suspects of being modulated. In this study, incommensurate ordering was found in satellites occurring in planes perpendicular to c*. The structure of Cd5(PO4)3Br was refined from single-crystal X-ray diffraction data in the four-dimensional super space group R:P3̄:(00γ): a = 16.932(2) Å, c = 6

Electrical resistivity of one-dimensional quasiperiodic η8-Cu5Sn4

The electrical resistivity, ρ, of one-dimensional quasiperiodic η8-Cu5Sn4 has been studied, and compared with crystalline Cu6Sn5 of identical basic structure (B8) and closely related atomic structure. ρ was measured between 1.5 and 300 K on needle-shaped crystals with their axes along the base lattice c direction, corresponding to the quasiperiodic direction in η8-Cu5Sn4. ρ (4 K) was found to be n