Crystal and magnetic structure of piezoelectric, ferrimagnetic and magnetoelectric aluminium iron oxide FeAlO₃ from neutron powder diffraction

Neutron diffraction, using FeAlO₃ polycrystalline samples at T = 30 K, reveals a classical Néel ferrimagnetism with strong `180 degrees Fe-O-Fe' superexchange antiferromagnetic interactions and an extremely weak spontaneous magnetization (0.38 ± 0.17 μ_B). Piezoelectricity originates in the bond arrangement on the tetrahedral sites.

X-ray structure refinement of (3 + 1)-dimensional incommensurate composite (1-x)Ta₂O₅.xWO₃, x = 0.1

The structure of the x = 0.1 member of the (1-x)Ta₂O₅.xWO₃ solid solution is described and compared with the structures of the x = 0.14 and x = 0.267 members.

Isotope effect on anharmonic thermal atomic vibration and κ refinement of ¹²C and ³C diamond

The anharmonic thermal vibration of atoms of ¹³C_x¹²C_1-x and the isotope dependence of their lattice constant have been examined after κ refinement.

Atomic displacement parameters for garnets: a lattice-dynamical evaluation

Lattice-dynamical calculation of atomic displacement parameters, IR and Raman spectra, and thermodynamic functions for natural garnets is shown. Evidence for disordered Mg and Fe atoms in pyrope and almandine, respectively, is given.

Theoretical study of the deformation densities of d electrons in K₂[PdCl₆] and K₂[PtCl₆] crystals

The deformation densities of d electrons in K₂[PdCl₆] and K₂[PtCl₆] crystals were analyzed by theoretical calculations using embedded cluster models.

Structure and optical non-linearity of PbO.2B₂O₃

The crystal structure of PbO.2B₂O₃ is described. Optical non-linearity measurements are also presented, which indicate that both phase-matchability and high non-linearity may be achieved by barium doping.

Structure of Mg₆SO₂(OH)₁₄ determined by micro single-crystal X-ray diffraction

The crystal structure of Mg₆SO₂(OH)₁₄ has been solved from single-crystal diffraction data collected on an extremely small crystal of dimensions ca 0.5 x 100 x 2.5 μm³ with synchrotron radiation. The structure is based on a stack of zigzag sheets composed of MgO₆ octahedra.

Structural investigation of homonuclear Pt₂ and heteronuclear PdPt complexes containing a metal–metal bond bridged by hydrido and sulfido ligands

The disordered room-temperature structure and ordered low-temperature structure of [Pt₂(μ-H)(μ-S)(dppe)₂](PF₆) are reported, together with the room-temperature structure of the corresponding PtPd complex. NMR spectroscopy confirms the genuine heteronuclear nature of the mixed-metal complex.

Crystal and molecular structures of 3-acetyl-5-[2-(3-ethyl-2-benzo­thiazol­idene)]ethylidenerhodanine and its lithium and sodium salts. Layered organic–inorganic structures

For the first time the J aggregation in the crystal of merocyanine dye is determined. The structure and stability of layered organic-inorganic structures with internal surfaces are discussed.

Structure at 200 and 298 K and X-ray investigations of the phase transition at 242 K of [NH₂(CH₃)₂]₃Sb₂Cl₉ (DMACA)

Studies on the mechanism of ferro-paraelectric phase transitions in DMACA are described. Temperature changes of Sb-Cl bond lengths of up to 0.3 Å were observed and attributed to the deformation of the lone-electron pair on the Sb^''' atom caused by N-H⋯Cl hydrogen bonds.

Modification of crystal structure of ammonium Rochelle salt [NaNH₄(+)-C₄H₄O₆.4H₂O] owing to the replacement of NH₄ ions with K ions

Modification of the crystal structure of ammonium Rochelle salt owing to the replacement of NH₄ with K ions is studied at room temperature. Differences in the accommodation ratios and the environment of the two types of NH₄ ion sites are given.

Four polymorphs of a cobaloxime complex with different solid-state photoisomerization rates

A quantitative relation has been obtained between the void space around the reactive group and the reaction rate in the photoisomerization of four crystal forms of a cobalt complex.

Structure of vanadocene in the temperature interval 108–357 K and the nature of the ring disorder

Multi-temperature X-ray diffraction analysis of the vanadocene Cp₂V single crystal at 108, 170, 297 and 357 K shows that crystal disorder in this compound has a dynamic nature, and at 108 K the crystal structure of Cp₂V is ordered. A model of the disordering at higher temperatures is supposed.

Structure of ammonium hydrogen succinate above and below the phase transition around 170K

No ordering of the H-atom positions in the short hydrogen bonds between hydrogen succinate ions occurs by the phase transition.

Structure of a twin initially solved from a partial data set: di-μ-chlorobis-[di-n-butyldi­thiocarbamato]dipalladium

The monoclinic cell assigned to the twins is not primitive (leading to overlap of hkl with h = ±3n) as originally supposed, but B-centred. This was discovered using a partial data set from which both h = ±3n and (h + l) = 2n + 1 had been removed. Reflexions h = ±3n do not in fact overlap and were restored for full refinement.

Structural studies on monohalogenated derivatives of the phytohormone indole-3-acetic acid (auxin)

Structural studies of natural chlorinated auxin, 4-chloroindole-3-acetic acid and other phenyl-substituted halogen derivatives, based on X-ray structure analysis and computational chemistry methods, are presented.

Structures of four o-nitrobenzo­nitriles

Three substituted o-nitrobenzonitriles show incipient intramolecular nucleophilic attack of a nitro O atom on the electrophilic nitrile C atom.

Structure of 1,3,5,7-tetra­nitro-3,7-di­azabi­cyclo-[3.3.0]octane. Structure solution from molecular packing analysis

Structure solution with the crystal structure prediction program MOLPAK, starting with a molecular mechanics geometry-optimized model, is described. An example of a polynitrodiazabicyclo[3.3.0]octane ring system is studied.

Effects of H/D substitution on thermal vibrations in piperazinium hexanoate-h₁₁,d₁₁

From neutron diffraction data collected at 15 K, mean-square nuclear displacements are obtained for the intramolecular H and D vibrations. The isotope effect is highly significant. For the hexanoate anion, normal-mode analysis using the force field from ab initio quantum mechanical calculations gives mean-square displacements for H and D which do not agree with the neutron diffraction results.

The crystal packing modes of three sterically overcrowded imidazole derivatives

4-Cyclohexylamino-5-hydroxy-1,5-diphenyl-Δ³-imidazolin-2-one crystallizes as a racemate, whereas the corresponding 4-tert-butylamino derivative occurs optically resolved.

The rare trans-syn thymine photodimers: structures of polyoxyethylene-linked bis­thymines and the derived trans-syn thymine photodimers. Comparison of the stereochemistry before and after photodimerization

The structural comparison of two trans-syn thymine photodimers with their respective parent compounds shows that the dimerization results in a strained geometry about the cyclobutane ring and a disturbed planarity of the thymines. The degree of such stereochemical changes, consequent to dimerization, depends on the nature of the linker backbone.

Structure of the charge-transfer salt 2,2',5,5'-tetraselena­fulvalene–7,7,8,8-tetra­cyano-p-quinodi­methane (TSeF–TCNQ)

The charge-transfer salt TSeF-TCNQ has the same segregated stack structure as TTF-TCNQ. Replacement of S by Se changes the relative importance of cation-cation and anion-anion stack interactions in the crystal.

Structure determination by X-ray crystallography by M. F. C. Ladd and R. A. Palmer