Structure of planar defects in tilted perovskites

Continuity of octahedral tilting in perovskite compounds necessarily leads to different tilt structures at planar defects such as domain walls.

Grazing-incidence small-angle X-ray scattering from a random rough surface: a self-consistent wavefunction approximation

An attempt is made to go beyond the distorted-wave Born approximation by using the integral wave equation adjusted with the Green function formalism in application to the grazing-incidence small-angle X-ray (GISAX) scattering from a random rough surface. The self-consistent approximation for the wavefunction is applied to obtain a basic solution of the non-averaged integral wave equation. The analytical expressions for the reflected GISAX specular and diffuse scattering intensities are obtained using the statistical model of a random Gaussian surface in terms of the r.m.s. roughness and two-point cumulant correlation function.

Variance of electron-density maps in space group P1

The variance of electron-density maps (observed, difference and hybrid) is estimated in P1 under the hypothesis that the phases are distributed about the correct values according to von Mises distributions.

Translation calibration of inverse-kappa goniometers in macromolecular crystallography

A rapid, easy-to-perform translation calibration procedure has been developed for use with the EMBL/ESRF mini-κ goniometer head and for other inverse-kappa goniometers designed for macromolecular crystallography. Regular calibration ensures the precision of experiments that rely on many degrees of freedom in crystal reorientation.

Simultaneous determination of highly precise Debye–Waller factors and multiple structure factors for chemically ordered tetragonal FePd

Large sets of highly precise and accurate structure factors and anisotropic Debye–Waller factors for the tetragonal chemically ordered and ferromagnetic intermetallic phase FePd were simultaneously obtained using multi-beam convergent-beam electron diffraction (CBED). The CBED pattern sensitivity to structure and Debye–Waller factor changes is assessed and the potential for bonding charge measurements in FePd is discussed.

Non-crystallographic nets with freely acting, non-abelian local automorphism groups

An infinite family of non-crystallographic nets is constructed and analysed.

Faulting in finite face-centered-cubic crystallites

The effects of faulting on the powder line profile are discussed, in particular considering the case of small crystalline face-centered-cubic domains.

On the symmetry and the signature of atomic mechanisms in multiferroics: the example of Ba₂CoGe₂O₇

The peculiar magnetoelectric properties of Ba₂CoGe₂O₇ are explained by making use only of symmetry arguments and symmetry-based phenomenology. This remarkable example shows the general need for a systematic application of magnetic symmetry in the study of multiferroics.

Exact direct-space asymmetric units for the 230 crystallographic space groups

A reference table of exact direct-space asymmetric units for the 230 crystallographic space groups is presented, based on a new geometric notation for asymmetric unit conditions.

About the σ_A estimate

A new set of statistical formulas estimating the σ_A parameter are described and their mean features are studied.

A charge-flipping algorithm to handle incomplete data

A version of the charge-flipping algorithm is introduced to handle incomplete data. The efficiency of the algorithm is thoroughly tested, and it is shown that many small-molecule structures can be solved by utilizing significantly fewer data than is standard in current crystallographic practice.

Conditional ambiguity of one-dimensional crystal structures determined from a minimum of diffraction intensity data

The method of elementary symmetric polynomials with a new origin definition is used to enumerate small one-dimentional crystal structures obtained from a minimum set of diffraction intensities.

The quality of precession electron diffraction data is higher than necessary for structure solution of unknown crystalline phases

It is shown that a reduction in data quality does not alter the success of structure solution of unknown crystals, with high accuracy of the cation positions. The accuracy of the light-atom positions may be slightly reduced.

Precession electron diffraction of Mn₂O₃ and PbMnO_2.75: solving structures where X-rays fail

The structures of Mn₂O₃ and PbMnO_2.75 have been solved from powder samples by precession electron diffraction data. The number of reflections measured appears to be the significant parameter for structure solution rather than precession angle, resolution limit and Lorentz-type correction.

Pseudo extra reflection conditions

The extra reflection conditions as given in International Tables for Crystallography Volume A may be violated if the atomic thermal vibrations and/or static disorder are anisotropic.

Comment on Probability density functions of the average and difference intensities of Friedel opposites by Shmueli & Flack (2010)

Comment on Shmueli & Flack [Acta Cryst. (2010), A66, 669–675].

Response to Olczak's comment on Probability density functions of the average and difference intensities of Friedel opposites

Response to Olczak's comment on Shmueli & Flack [Acta Cryst. (2010), A66, 669–675].