Acta Crystallographica Section A

Foundations of Crystallography

Volume 68, Part 4 (July 2012)


	Cover illustration: The sequence of constructing the cartwheel pattern of the first-level hierarchy of the quasi-periodic pattern on the interior walls of the courtyard of the Madrasa of al-'Attarin (1323), Fez, Morocco [Al Ajlouni (2012). Acta Cryst. A68, 235-243].

research papers
obituaries
books received

research papers

Acta Cryst. (2012). A68, 435-442 [ doi:10.1107/S0108767312013001 ]

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

B. Dittrich, E. Sze, J. J. Holstein, C. B. Hübschle and D. Jayatilaka

Synopsis: 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.

Online 1 May 2012

Acta Cryst. (2012). A68, 443-447 [ doi:10.1107/S0108767312013189 ]

Elastic propagation of fast electron vortices through crystals

S. Löffler and P. Schattschneider

Synopsis: 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.

Online 1 May 2012

Acta Cryst. (2012). A68, 448-451 [ doi:10.1107/S0108767312014535 ]

Enhanced rigid-bond restraints

A. Thorn, B. Dittrich and G. M. Sheldrick

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

Online 1 May 2012

Acta Cryst. (2012). A68, 452-463 [ doi:10.1107/S0108767312016571 ]

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

N. Dadda, A. Nassour, B. Guillot, N. Benali-Cherif and C. Jelsch

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

Online 10 May 2012

Acta Cryst. (2012). A68, 464-469 [ doi:10.1107/S0108767312015772 ]

A practical study of the electron-density-map variance

C. Giacovazzo and A. Mazzone

Synopsis: 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.

Online 15 May 2012

Acta Cryst. (2012). A68, 470-483 [ doi:10.1107/S0108767312018910 ]

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

J.-F. Sadoc, N. Rivier and J. Charvolin

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

Online 8 June 2012

Acta Cryst. (2012). A68, 484-493 [ doi:10.1107/S0108767312019034 ]

A topological method for the classification of entanglements in crystal networks

E. V. Alexandrov, V. A. Blatov and D. M. Proserpio

Synopsis: 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.

Online 14 June 2012

Acta Cryst. (2012). A68, 494-504 [ doi:10.1107/S0108767312014705 ]

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

P. Dub and O. Litzman

Synopsis: 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.

Online 10 May 2012

Acta Cryst. (2012). A68, 505-512 [ doi:10.1107/S0108767312017448 ]

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

F. N. Chukhovskii

Synopsis: 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.

Online 30 May 2012

Acta Cryst. (2012). A68, 513-520 [ doi:10.1107/S0108767312022751 ]