Crystal growth and twinned crystal structure of Sr₂CaWO₆

The structure of the double perovskite Sr₂CaWO₆ has been refined using X-ray single-crystal data. Samples have been grown by sintering at high temperature. The model includes a quantitative description of the twinning expected for these compounds.

Superspace description of the homologous series Ga₂O₃(ZnO)_m

A unified description for structures in the homologous series Ga₂O₃(ZnO)_m is presented using the superspace formalism. The structures of phases m = 6 and m = 9 were refined using the proposed model.

Modulation functions of incommensurately modulated Cr₂P₂O₇ studied by the maximum entropy method (MEM)

The MEM provides a description of the atomic modulations within the ordered and disordered regions of incommensurate Cr₂P₂O₇, from its application to X-ray diffraction data of this compound.

Mullite-type Ga₄B₂O₉: structure and order–disorder phenomenon

The structure of Ga₄B₂O₉ is solved from powder X-ray diffraction data and refined by Rietveld analysis. The order–disorder phenomenon in the structure is elucidated by the construction of the fundamental building units.

Two new silicate structures based on a rhodesite-type heteropolyhedral microporous framework

The structures of two new synthetic silicates based on a rhodesite-type heteropolyhedral framework are reported and peculiar microporous features of the group are discussed.

New RE microporous heteropolyhedral silicates containing 4¹5¹6¹8² tetrahedral sheets

The crystal chemical features of heteropolyhedral microporous silicates A₃RESi₆O₁₅·2.25H₂O (A = Na, K, H₃O; RE = rare earths La, Ce, Eu) based on 4¹5¹6¹8² tetrahedral sheets are discussed.

Re-investigation of the structure and crystal chemistry of the Bi₂O₃–W₂O₆ `type (Ib)' solid solution using single-crystal neutron and synchrotron X-ray diffraction

The crystal structure of the floating-zone furnace-grown crystal Bi_35.66W_4.34O_66.51 was determined from simultaneous refinements against single-crystal neutron and synchrotron X-ray data.

Inorganic structures in space group P31m; coordinate analysis and systematic prediction of new ferroelectrics

Analysis of the 62 entries under the polar space group P31m listed in the ICSD release 2009/1 reveals that 11 of the 31 crystallographic families present are candidates for possessing the property of ferroelectricity. New among them are the minerals schairerite, galeite and lizardite in addition to the materials LaNi₅D₆, [N(CH₃)₄]₂Mo₃S₁₃, Li₁₇Ag₃Sn₆ and Cs₃As₅O₉.

Maximum entropy method and charge flipping, a powerful combination to visualize the true nature of structural disorder from in situ X-ray powder diffraction data

Disorder in α-Rb₂[C₂O₄] and α-Rb₂[CO₃] is studied by the application of the maximum entropy method (MEM) to X-ray powder diffraction data, employing phases of reflections from various sources. The MEM applied to reflection phases from charge-flipping combined with amplitudes from a Le Bail extraction provide an ab initio description of the structural disorder in these compounds.

1,1′-Fc(4-C₆H₄CO₂Et)₂ and its unusual salt derivative with Z′ = 5, catena-[Na⁺]₂[1,1′-Fc(4-C₆H₄CO₂⁻)₂]·0.6H₂O [1,1′-Fc = (η⁵-(C₅H₄)₂Fe]

The neutral diethyl 4,4′-(ferrocene-1,1′-diyl)dibenzoate, 1,1′-Fc(4-C₆H₄CO₂Et)₂ [1,1′-Fc = η⁵-(C₅H₄)₂Fe], yields the complex salt with Z′ = 5, poly[disodium bis[diethyl 4,4′-(ferrocene-1,1′-diyl)dibenzoate] 0.6-hydrate], poly-[Na⁺]₂[η⁵-(C₅H₄)₂Fe(4-C₆H₄CO)₂]·0.6H₂O, crystallized with difficulty as small red crystals over 4 weeks from a water/dimethylformamide/pyridine (2:2:1) solution. The asymmetric unit as poly-[Na⁺]₁₀[η⁵-(C₅H₄)₂Fe(4-C₆H₄CO)₂]₅·3H₂O comprises five dianions stacked about a central two-dimensional layer of ten Na⁺ ions and three water molecules.

Change in electronic structure in a six-coordinate copper(II) complex accompanied by an anion order/disorder transition

The complex [Cu(L^OH)₂][ClO₄]₂·2(CH₃)₂CO [L^OH = 2,6-bis(hydroxyiminomethyl)pyridine] undergoes an abrupt structural rearrangement on cooling to 157 ±3 K. This involves a change in the Jahn–Teller distortion of the complex, a crystallographic ordering of a perchlorate ion, and significant displacements of the two lattice acetone molecules.

More examples of the 15-crown-5⋯H₂O—M—OH₂⋯15-crown-5 motif, M = Al³⁺, Cr³⁺ and Pd²⁺

Five co-crystals grown from aqueous solutions equimolar in 15-crown-5 and [M(H₂O)₆](NO₃)_n, M = Al³⁺, Cr³⁺ and Pd²⁺, all contain hydrogen-bonded stacks in which metal complexes containing the fragment trans-H₂O—M—OH₂ alternate with 15-crown-5 molecules. A survey of the literature found 41 structures containing similar stacks.

Proton-transfer dynamics in the (HCO₃⁻)₂ dimer of KHCO₃ from Car–Parrinello and path-integrals molecular dynamics calculations

The proton-transfer mechanism cannot be described as strictly simultaneous or successive as situations close to both of these scenarios were observed.

Predicted crystal structures of tetra­methylsilane and tetra­methylgermane and an experimental low-temperature structure of tetra­methylsilane

The crystal structures of tetramethylsilane, Si(CH₃)₄, and tetramethylgermane, Ge(CH₃)₄, were predicted by global lattice-energy minimizations. For tetramethylsilane, a low-temperature structure at 100 K could be determined from single-crystal X-ray diffraction data.

Universal prediction of intramolecular hydrogen bonds in organic crystals

A complete exploration of intramolecular hydrogen bonds (IHBs) has been undertaken using a combination of statistical analyses of the Cambridge Structural Database and computation of ab initio interaction energies for prototypical hydrogen-bonded fragments. The findings contribute to a new method to predict IHB likelihood in generic organic crystal structures. Predictivity in excess of 90% has been obtained.

L-2-Aminobutyric acid: two fully ordered polymorphs with Z′ = 4

The two closely related polymorphs of L-aminobutyric acid are divided into hydrophilic layers and hydrophobic layers, the latter being exceptionally thin with unique pseudo-centers-of-symmetry.

Precursor effects of the orthorhombic to monoclinic phase transition in benzocaine form (II) revealed by X-ray diffuse scattering

A Monte Carlo computer model has been developed for the room-temperature form (II) polymorph of benzocaine that incorporates, on a local scale, structural features derived from the low-temperature form (III) polymorph. This convincingly reproduces those observed diffraction features that an earlier simple harmonic model was unable to achieve.