A two-dimensional polymer (2DP) based on the dimerization of anthraceno groups arranged in a triptycene motif is reported. A photoinduced polymerization is performed in the crystalline state and gives a lamellar 2DP via a crystal-to-crystal (but not single-crystal to single-crystal) transformation. Solvent-induced exfoliation provides monolayer sheets of the 2DP. The 2DP is considered to be a tiling, a mathematical approach that facilitates structural elucidation.

The nanocrystalline αII-phase of the industrially produced organic pigment quinacridone was studied by 3D electron diffraction. The average crystal structure was obtained directly from the data and validated by energy minimization. A model describing the experimentally observed diffuse scattering was proposed.

A method to refine organic crystal structures from powder diffraction data with incorrect lattice parameters has been developed. The method is based on the similarity measure developed by de Gelder et al. [J. Comput. Chem. (2001), 22, 273-289], using the cross- and auto-correlation functions of a simulated and an experimental powder pattern. The lattice parameters, molecular position, molecular orientation and selected intramolecular degrees of freedom are optimized until the similarity measure reaches a maximum; subsequently, a Rietveld refinement is carried out. The program FIDEL (FIt with DEviating Lattice parameters) implements this method. The procedure is also suitable for unindexed powder data, powder diagrams of very low quality and powder diagrams of non-phase-pure samples. Various applications are shown, including structure determinations from powder data using crystal structure predictions by standard force-field methods. Other useful applications include the automatic structure determination from powder data starting from the crystal structures of isostructural compounds (e.g. a solvate, hydrate or chemical derivative), or from crystal data measured at a different temperature or pressure.

The Red carrying the news around the world: Most newspapers and journals worldwide (including Angewandte Chemie) are printed with Pigment Red 57:1. The crystal structures of this pigment in various hydration states have now been determined by X‐ray powder diffraction.

Local structures and energies were calculated for the interaction of acetone molecules with ice I h at the (0001) surface, in the bulk and at small-angle grain boundaries. Force-field methods were used; for the surface additionally ab initio calculations were done. An ordered crystal-structure model of ice I h in space group P112 1 (Z ¼ 8) was used. The small-angle grain boundary was set up as a series of line defects with Burgers vectors of [2/3 1/3 1/2] (in the hexagonal lattice of ice I h ). All calculations were carried out with one or two acetone molecules in a sufficiently large simulation box containing up to 4608 water molecules, representing the low concentration of acetone in the atmosphere. The adsorption on the surface is energetically preferred. The acetone molecule is bound to the surface by two hydrogen bonds. This result is in contrast to earlier works with high acetone concentrations where only one hydrogen bond is formed. With two hydrogen bonds the adsorption enthalpy is calculated as À41.5 kJ mol À1 , which is in agreement with experimental results. The interaction at small-angle grain boundaries is energetically less favourable than at the surface but much more favourable than in the bulk ice. In bulk ice and at small-angle grain boundaries the acetone molecule is bound by two hydrogen bonds like at the surface. The incorporation of acetone in bulk ice distorts the crystal structure significantly, whereas an incorporation at a small-angle grain boundary leads only to a minor distortion.