SHELX makes an impact

The 2009 impact factor for Acta Crystallographica Section A is discussed.

Data scaling and temperature calibration in time-resolved photocrystallographic experiments

Relative scaling of light-on and light-off data from photocrystallographic experiments and the correction for temperature differences between the two data sets are discussed.

Simple tilings by polyhedra with five- and six-sided faces

Periodic tilings by polyhedra with five- and six-sided faces with up to 11 kinds of vertex in the tiling are described.

X-ray specular scattering from statistically rough surfaces: a novel theoretical approach based on the Green function formalism

The influence of multiple diffuse scattering effects upon the reflection and transmission coefficients in the case of grazing X-ray specular scattering from statistically rough surfaces is investigated. The statistical properties of the rough surface are described in terms of the r.m.s. roughness σ and correlation length ξ of the two-point height–height correlation function.

Magnetic space and superspace groups, representation analysis: competing or friendly concepts?

An approach based on irreducible representations of the paramagnetic space group is used to find the ordering of magnetic moments induced by a magnetic phase transition. The combination of representation analysis and magnetic symmetry is the most effective way to analyze magnetic ordering and refine magnetic structures.

The influence of different Student's T mosaic distributions on the extinction factor in mosaic crystals

The influence of different Student's T mosaic distributions upon the integrated reflection power ratio and the secondary extinction factor in mosaic crystals is presented.

Double-slit dynamical diffraction of X-rays in ideal crystals (Laue case)

The double-slit dynamical diffraction of X-rays in perfect crystals is theoretically investigated. It is shown that interference fringes similar to Young's fringes are formed on the exit surface of a crystal.

Probability density functions of the average and difference intensities of Friedel opposites

Exact probability density functions of the average (A) and difference (D) intensities of Friedel opposites have been derived and were favourably compared with histograms of A and D, which were simulated as well as recalculated from a published solved P1 structure.

Is there a fundamental upper limit for the significance I/σ(I) of observations from X-ray and neutron diffraction experiments?

The limits of significance due to Poisson statistics have been investigated and theoretical agreement factors were calculated which may serve as benchmark values.

Determination of Debye–Waller factor and structure factors for Si by qu­antitative convergent-beam electron diffraction using off-axis multi-beam orientations

Energy-filtered convergent-beam electron diffraction patterns of Si were obtained by transmission electron microscopy at different temperatures. Off-axis multi-beam orientations offer improved accuracy for simultaneous refinements of multiple structure factors and Debye–Waller factors, which is attributed to strong dynamical interactions between diffracted beams with each other and the transmitted beam.

Simultaneous determination of highly precise Debye–Waller factors and structure factors for chemically ordered NiAl

Debye–Waller and structure factors for B2 ordered simple cubic NiAl were obtained from elastically filtered off-zone-axis multi-beam convergent-beam electron diffraction patterns at different temperatures. The Debye–Waller factors for Al and Ni were shown to be equal at a cross-over temperature of ~90 K.

X-ray diffraction peaks from correlated dislocations: Monte Carlo study of dislocation screening

X-ray diffraction peak profiles are calculated by the Monte Carlo method for different types of dislocation correlations. General conditions for screening of the long-range dislocation strain are derived and implemented.

Volume of intersection of two balls in orientation space

Orientations deviating from an ideal orientation by angles not exceeding a fixed limit constitute a ball. A formula for the volume of the intersection of two such balls is derived.

David H. Templeton (1920–2010)

Obituary for David H. Templeton.

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