Celebrating the past, looking to the future

Four articles from Acta Crystallographica Section A feature in the list of the top 100 most highly cited papers. The new Advances section looks set to continue the trend and is attracting articles with high potential impact and broad appeal.

SHELXT – Integrated space-group and crystal-structure determination

SHELXT automates routine small-molecule structure determination starting from single-crystal reflection data, the Laue group and a reasonable guess as to which elements might be present.

Nuclear-weighted X-ray maximum entropy method – NXMEM

NXMEM is a new method to reconstruct pseudo nuclear-density distributions from X-ray diffraction data. It is validated against simulated and experimental data on two disordered systems, PbTe and Ba₈Ga₁₆Sn₃₀.

Diffuse multiple scattering

A new form of diffraction lines similar to Rutherford, Kikuchi and Kossel lines has been identified. They can be used to eliminate the need for sample/source matching in Lonsdale's triple convergent line method in lattice-parameter determination.

Prediction of molecular crystal structures by a crystallographic QM/MM model with full space-group symmetry

A new crystallographic quantum-mechanical/molecular-mechanical model for the prediction of molecular crystal structures is described. Applications include polymorphic systems and molecules from the CCDC blind tests of crystal structure prediction.

From direct-space discrepancy functions to crystallographic least squares

Crystallographic least-squares properties are derived from discrepancy functions working in direct space.

Analysis of rapidly synthesized guest-filled porous complexes with synchrotron radiation: practical guidelines for the crystalline sponge method

This report describes complete practical guidelines and insights for the crystalline sponge method, which have been derived through the first use of synchrotron radiation on these systems, and includes a procedure for faster synthesis of the sponges. These guidelines will be applicable to crystal sponge data collected at synchrotrons or in-house facilities, and will allow researchers to obtain reliable high-quality data and construct chemically and physically sensible models for guest structural determination.

The anatomy of a comprehensive constrained, restrained refinement program for the modern computing environment – Olex2 dissected

An in-depth presentation is given of olex2.refine, the new refinement engine integrated in the Olex2 program.

An alternative method for the calculation of joint probability distributions. Application to the expectation of the triplet invariant

An explanation is given of the method for the calculation of expectation values by sampling over atomic distributions.

High-symmetry embeddings of interpenetrating periodic nets. Essential rings and patterns of catenation

Crystallographic and catenation data are given for embeddings of interpenetrating sets of common 2- and 3-periodic nets.

Direct phasing of protein crystals with high solvent content

An iterative transform algorithm is proposed for extracting the phases of X-ray reflections directly from the diffraction intensity data of protein crystals with high solvent content. Examples of successful trial calculations carried out with real diffraction data are presented.

Symmetry groups associated with tilings on a flat torus

This work investigates the symmetry and color-symmetry properties of transitive tilings embedded on a flat torus and their geometric realizations as tilings on a round torus. The realizations are used to model nanotori.

Scanning of two-dimensional space groups

Scanning tables of two-dimensional space groups are presented.

Report of the Executive Committee for 2013