New capabilities for `colouring in' the chemistry of crystal defects atom-by-atom

The latest generation of scanning transmission electron microscopes equipped with high-efficiency energy-dispersive X-ray detectors are breaking new ground with respect to high-resolution elemental imaging of materials. In this issue, Paulauskas et al. [Acta Cryst. (2014), A70, 524–531] demonstrate impressive results when applying this technique to improve understanding of CdTe dislocation structures.

Atomic scale study of polar Lomer–Cottrell and Hirth lock dislocation cores in CdTe

Using atomic-column-resolution high-angle annular dark-field imaging and X-ray spectrum imaging in an aberration-corrected scanning transmission electron microscope, dislocation core structures in zinc-blende CdTe are examined. The formation mechanisms of the polar core structures is described using Thompson's tetrahedron adapted to reactions of polar dislocations as they appear in CdTe and other zinc-blende solids.

Unconstrained and X-ray constrained extremely localized molecular orbitals: analysis of the reconstructed electron density

Experimentally constrained wavefunctions are calculated for α-glycylglycine using high-resolution X-ray structure factors and the extremely localized molecular orbital formalism.

High-flux ptychographic imaging using the new 55 µm-pixel detector `Lambda' based on the Medipix3 readout chip

The Large Area Medipix-Based Detector Array (Lambda) has been used in a ptychographic imaging experiment on solar-cell nanowires. By using a semi-transparent central stop, the high flux density provided by nano-focusing Kirkpatrick–Baez mirrors can be fully exploited for high-resolution phase reconstructions.

A study of one-dimensional incommensurate modulated structure determination in high-resolution transmission electron microscopy

An approach has been developed for the first time to determine the displacive and substitutional modulation functions of an incommensurate modulated structure from a limited-size high-resolution transmission electron microscope image and electron-diffraction data.

An algorithm for calculating diffraction profiles of 2θ scans for multiple diffraction from crystals and thin films

An algorithm for calculating the 2θ diffraction profiles is developed based on the dynamical theory of X-ray diffraction for multi-beam cases. The connection between the 2θ-scanned profiles and the excitation of modes is revealed.

Convergent-beam electron-diffraction-pattern symmetry of nanodomains in complex lead-based perovskite crystals

The symmetry of complex nanodomain structures in lead-based perovskite crystals is determined using convergent-beam electron-diffraction patterns along different zone axes based on dynamic diffraction simulations.

Orthorhombic sphere packings. V. Trivariant lattice complexes of space groups belonging to crystal class 222

All homogeneous sphere packings were derived that refer to the trivariant orthorhombic lattice complexes of the space groups belonging to crystal class 222.

Twelvefold symmetric quasicrystallography from the lattices F₄, B₆ and E₆

Twelvefold symmetric quasicrystallographic structures are obtained from the projections of the lattices described by the Coxeter–Weyl groups W(F₄), W(B₆) and W(E₆). The strip-projection technique leads to results compatible with some experimental data.

Finite noncrystallographic groups, 11-vertex equi-edged triangulated clusters and polymorphic transformations in metals

The one-to-one correspondence between a set of cosets of the Mathieu group M₁₁, block sets of the Steiner system S(4, 5, 11) and 11-vertex equi-edged triangulated clusters determines symmetry-allowable transformations between different 11-vertex triangulated clusters as automorphisms of the Steiner system S(4, 5, 11). The transformations can describe local reconstructions corresponding to polymorphic transformations in metals.

Use of bond-valence sums in modelling the diffuse scattering from PZN (PbZn_1/3Nb_2/3O₃)

Diffuse scattering from PZN (PbZn_1/3Nb_2/3O₃) has been analysed by combining the average structure revealed by Bragg diffraction with the requirements of the bond-valence sum. This goes beyond previous models, which are more prescriptive and artificial in nature, although not all key aspects of the short-range order can be shown to arise `naturally' out of the modelled interactions.

An accurate parameterization for scattering factors, electron densities and electrostatic potentials for neutral atoms that obey all physical constraints

An efficient procedure and computer program have been developed to perform an accurate parameterization for scattering factors with the correct inclusion of all physical constraints.

Icosahedral symmetry breaking: C₆₀ to C₇₈, C₉₆ and to related nanotubes

The structure of a particular type of hollow cage fullerenes (C_60+N18) is described in detail, and their existence explained from a symmetry-breaking mechanism starting from the perfect icosahedral symmetry of C₆₀ to specific subgroups A₂. This mechanism expands previous results describing the existence of other groups of fullerenes (C_60+N10) based on the breaking of the icosahedral symmetry of C₆₀ to the subgroup H₂. The mechanism is extended to describe the cases that generate carbon nanotubes, as well as stereoisomers of the C₇₈ molecule.

The coincidence problem for shifted lattices and crystallographic point packings

The coincidence problem for lattices, shifted lattices and crystallographic point packings is considered. The results are illustrated using a shifted square lattice and the diamond packing.

An alternative method for data analysis in serial femtosecond crystallography

A new diffraction data analysis method for serial femtosecond crystallography is proposed. This method is found to obtain satisfactory results.

Seitz symbols for symmetry operations of sub­periodic groups

Revised Seitz notation is provided for the symmetry operations blocks of International Tables for Crystallography Vol. E, Subperiodic Groups.

Accurate atomic displacement parameters from time-of-flight neutron-diffraction data at TOPAZ

Accurate atomic displacement parameters obtained from time-of-flight single-crystal diffraction neutron data, collected at the newly commissioned SNS beamline TOPAZ, are presented for two organic crystals and compared to those obtained from four alternative methods: experimental charge-density modelling, high-order independent-atom models, estimates from combined TLS analysis and literature values as implemented in SHADE, and Hirshfeld atom refinement based on X-ray diffraction data.

Density functional calculations of polysynthetic Brazil twinning in α-quartz. Corrigenda and addenda

Two corrections and a number of additions are made to the article by Grimmer & Delley [Acta Cryst. (2012>), A68, 359–365].

Effects of merohedric twinning on the diffraction pattern. Erratum and corrigenda

A number of corrections are made to the article by Nespolo et al. [Acta Cryst. (2014), A70, 106–125].

Prices of IUCr journals