Crystal-field effects in L-homoserine: multipoles versus quantum chemistry

Crystal-field effects in the non-standard amino acid L-homoserine were investigated. Benchmark results from periodic B3LYP calculations are well reproduced by point-charge models. Basis-set representations of the electron density show subtle features further away from the nuclei, which cannot be retrieved by the Hansen/Coppens multipole model.

Elastic propagation of fast electron vortices through crystals

The propagation of electron vortices in crystals is studied numerically. It is found that angular momentum is exchanged between the probe beam and the crystal lattice.

Enhanced rigid-bond restraints

An extension is proposed to the rigid-bond description of atomic thermal motion in crystals.

Charge-density analysis and electrostatic properties of 2-carb­oxy-4-methylanilinium chloride mono­hydrate obtained using a multipolar and a spherical-charges model

The multipolar electron distribution of the title compound was compared with a spherical-charge modelling of the atoms, bonding density and lone pairs.

A practical study of the electron-density-map variance

An algorithm for the calculation of the variance of electron-density maps via fast Fourier transform is proposed. A study of the related features is described.

Phyllotaxis: a non-conventional crystalline solution to packing efficiency in situations with radial symmetry

Phyllotaxis builds a homogeneous self-similar distribution of points inside a flat disc.

A topological method for the classification of entanglements in crystal networks

A rigorous method is proposed to describe and classify the topology of entanglements between periodic networks if the links are of the Hopf type. The catenation pattern is unambiguously identified by the so-called Hopf ring net, which consists of barycentres of catenating rings with edges corresponding to the Hopf links.

Multiple wave scattering on a bordered crystal. Translation symmetry breaking and forbidden reflections

The interaction of a scalar wave with a single Si crystal is treated using Ewald's self-consistent field method. The reflectivities of allowed and forbidden reflections in the Bragg geometry valid for both coplanar and non-coplanar cases are derived. It is shown that there exists a very narrow reflectivity peak of the forbidden reflection.

On the optical theorem applicability using a self-consistent wave approximation model for the grazing-incidence small-angle X-ray scattering from rough surfaces

Based on a self-consistent wave approximation for solving the integral wave equation, the grazing-incidence small-angle X-ray scattering from a random rough surface is considered to test the applicability of the optical theorem.

Estimates of triplet invariants given a model structure

The triplet structure invariant is probabilistically estimated when a model structure with imperfect isomorphism is available.

David Sayre (1924–2012)

Obituary for David Sayre.

Structure of Materials. An Introduction to Crystallography, Diffraction and Symmetry