Unifying cluster-based structure models of decagonal Al–Co–Ni, Al–Co–Cu and Al–Fe–Ni

The building principles of Al-based decagonal quasicrystals and their approximants are discussed from a geometrical point of view.

Modulated structure of nepheline

The modulated structure of natural nepheline has been determined using the superspace approach.

Structures of two new high-pressure forms of AlPO₄ by X-ray powder diffraction and NMR spectroscopy

The crystal structures of two new high-pressure AlPO₄ phases synthesized at 6–7 GPa and 1523–1773 K are reported. Both phases contain doubly bent chains composed of six edge-shared Al polyhedra linked by PO₄ tetrahedra.

Investigation of the structure and phase transitions of the polymeric inorganic–organic hybrids: [M(Im)₄V₂O₆]_∞; M = Mn, Co, Ni, Im = imidazole

The polymeric isomorphous hybrid inorganic–organic vanadium oxide compounds [M(Im)₄V₂O₆]_∞, M = Mn, Co, Ni, Im = imidazole, were investigated between 100 (2) and 295 (2) K by single-crystal X-ray diffraction. The compounds contain two-dimensional polymeric sheets packed perpendicularly to c* and undergo a reversible order–disorder phase transition. The room-temperature P4₂/n disordered phase (Z = 8) is reversibly transformed to the I4₁/a ordered phase (Z = 32) below 281 K for the Mn and 175 K for the Co compounds, requiring a change of the hydrogen-bond connectivity for two of the eight imidazoles per asymmetric unit of the I4₁/a structure. The ordered phase of the Ni compound was found to have the space group P2/n (Z = 8) at 100 K. Models for the phase-transition mechanisms are considered.

Temperature-dependent analysis of thermal motion, disorder and structures of tris­(ethylenedi­amine)zinc(II) sulfate and tris­(ethylenedi­amine)copper(II) sulfate

The structures of the isostructural title compounds have been determined at multiple temperatures. The disorder in the cation due to hydrogen bonding and/or ring puckering and the Jahn–Teller effect were analyzed using a rigid-body model and normal coordinate analysis.

Structural analysis and multipole modelling of quercetin monohydrate – a qu­antitative and comparative study

A new crystal structure of quercetin monohydrate determined by X-ray diffraction is described. A transferred aspherical atom model is used for electron-density modelling. The resulting electron-density distribution and derived quantities are compared with the theoretical multipolar atom model.

Failures of fractional crystallization: ordered co-crystals of isomers and near isomers

A list of stoichiometric, ordered, molecular co-crystals of isomers, near isomers and molecules that are almost the same has been compiled in order to understand better the circumstances under which fractional crystallization is likely to fail.

Conformation and geometry of cyclo­propane rings having π-acceptor substituents: a theoretical and database study

There is excellent agreement between torsional distributions from crystal structure data and torsional energy profiles computed using DFT for a range of π-acceptor substituents attached to cyclopropane. Asymmetry in ring bond lengths is also highly comparable in the crystal structure and computational results.

Notes for authors 2011