Novel tools for visualizing and exploring intermol­ecular interactions in molecular crystals

Hirshfeld surfaces reflect intermolecular interactions in a novel visual manner, and features characteristic of different interactions can be revealed and highlighted by colour mapping of a variety of functions. A complementary two-dimensional mapping provides a quantitative summary of the intermolecular contacts experienced by molecules in the bulk. These tools provide a new approach to exploring packing modes and intermolecular interactions in molecular crystals, and are used to compile a comprehensive pictorial glossary of intermolecular interactions.

The compression mechanism of CrF₃

The structure of CrF₃ has been studied in the pressure range from ambient to 9.12 GPa. It was found that volume reduction is achieved through rotation of the CrF₆ octahedra, and a small octahedral strain was found to develop during compression. The zero-pressure bulk modulus B_o and its pressure derivative B were determined to be B_o = 29.2 (4) GPa and = 10.1 (3).

Octahedral tilting in cation-ordered perovskites – a group-theoretical analysis

Group-theoretical methods have been used to enumerate structures that arise when B-site cation ordering, as may occur in the 1:2 and 1:3 ordered perovskites A₃BBX₉ and A₄BBX₁₂, is combined with simple octahedral tilting. The numbers of possible structures are 10 and 11 for the 1:2 and 1:3 ordering patterns, respectively.

Structures of stable and metastable Ge₂Sb₂Te₅, an intermetallic compound in GeTe–Sb₂Te₃ pseudobinary systems

Crystal structures of stable and metastable Ge₂Sb₂Te₅, which is a material for phase-change memory, were investigated in detail by powder X-ray diffraction using SPring-8, a synchrotron radiation facility.

Structure refinements of Na_0.8Ti_1.2Ga_4.8O₁₀: X-ray diffraction analysis for the sodium ion distribution in a one-dimensional tunnel-like space

The anions of Na_0.8Ti_1.2Ga_4.8O₁₀ form a network that includes tunnels, within which the Na⁺ ions are found. The distribution of the Na⁺ ions, which may have large displacements from their mean position, was determined from X-ray diffraction data measured at 299, 173 and 123 K.

Transmission electron microscopy and electron diffraction study of the short-range ordering structure of α-LiFeO₂

The short-range ordered structure of the cations in α-LiFeO₂ was analysed by transmission electron microscopy and electron diffraction. The short-range ordering in α-LiFeO₂ is usually characterized by octahedral clusters, but it has been found that a local cation ordering is also characterized by both an alternate-distribution model and by cubic clusters.

Phase transitions in K₂Cr₂O₇ and structural redeterminations of phase II

The first-order transition in K₂Cr₂O₇ between phases I and II is fully described. A comparable transition between phases IIb and I is likely but not between phases II and IIb. An intermediate phase may exist between phases IIb and I.

Structural chemistry of new lithium bis­(oxalato)­borate solvates

The crystal structures of lithium bis(oxalato)borate salts solvated with water, acetonitrile, acetone, dimethoxyethane, 1,3-dioxolane and ethylene carbonate are reported.

Parameterization of the close packing of molecules in the unit cell

The analysis of histograms of pattern coefficients (cell length/molecular dimension) for thousands of crystal structures has shown that molecular crystal structures are fundamentally very similar to one another.

Di-p-bromo­phenyl ether, a redetermined crystal structure derived from low-quality diffraction data

An artificial data set, produced by scaling and merging six independent and individually unsatisfactory data sets from different crystals, has permitted the successful redetermination of the structure of the title compound, C₁₂H₈Br₂O.

Structural investigations of phosphorus–nitrogen compounds. 6. Relationships between molecular parameters in per-X-substituted bridged spermine derivatives and basicity constants ΣαR of substituents

The synthesis and crystal structures of six new per-substituted spermine-bridged cyclotriphosphazenes, [N₃P₃X₄(NHCH₂CH₂CH₂N)CH₂CH₂]₂ (where X = OPh, [spiro-O(CH₂)₃O]_0.5, Ph, NHPh, NC₄H₈ and NHBu^t, respectively) are reported and the observed relationship between molecular parameters of the N₃P₃ ring and substituent basicity constants is discussed.

Geometry of the 2-aminoheterocyclic–carboxylic acid R₂²(8) graph set: implications for crystal engineering

The geometry of the graph set formed between a 2-aminoheterocyclic ring containing an Nsp² atom (in the 1-position of the ring) and a carboxylic acid has been studied by collating data from known structures from the CSD. Unexpected differences were found to occur between both the non-hydrogen contact distances, and specific bond distances and angles of the heterocycle.

Different forms of antiparallel stacking of hydrogen-bonded antidromic rings in the solid state: polymorphism with virtually the same unit cell and two-dimensional isostructurality with alternating layers

The polymorphism of trans-2-hydroxycycloheptanecarboxylic acid with virtually the same unit cell is a special case of two-dimensional isostructurality with alternating (parallel versus antiparallel) layers. A similar phenomenon is exhibited by the analogous trans-2-hydroxy cycloheptanecarboxamide and its cyclopentane homolog.

Structure for perovskites with layered ordering of A-site cations. Erratum

Erratum to Acta Cryst. B60, 249–251.