issue contents

ISSN: 2053-2733

September 2010 issue

Highlighted illustration

Cover illustration: A collage of related patterns that are formed via tilings of the hyperbolic plane. Two-dimensional `universal tilings' (e.g. UQC473) of hyperbolic space can be wrapped onto a three-periodic minimal surface (e.g. the  gyroid), forming a curvilinear `Epinet tiling' (EGC473) whose edges relax to give a `Systre net', sqc14527. This approach to net enumeration is described in Ramsden et al. [Acta Cryst. (2009), A65, 81-108]. Further examples are collected at

structural transitions in solids

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A selection of papers from the CECAM/SimBioMa workshop on `Structural Transitions in Solids: Theory, Simulations, Experiments and Visualization Techniques' held in Lugano, 8–11 July 2009, are introduced.

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An ensemble of crystal structures can be modeled as a set of points in a high-dimensional space (fingerprint space) equipped with a suitable distance measure. This modeling method allows the use of multidimensional data-analysis tools to extract unique results from runs of the evolutionary structure predictor USPEX and is a useful tool in the study of crystal-structure sets and global chemical features of the energy landscape.

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The energy landscape concept, serving as the foundation of a deductive approach to solid-state chemistry, is applied to the theoretical prediction and synthetic realization of new crystalline compounds.

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A combination of different molecular-scale modeling approaches is used to study the phase stability and phase transition mechanisms in MgSiO3 pyroxenes.

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The interactive visualization of quantum-chemistry data using graphics hardware is described.

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The nonlinear enhancement in energy storage capacity of polyvinylidene fluoride polymer is explained on the basis of a phase transition from nonpolar to polar structures. The energy storage capacity is found to be several times larger than existing polymer materials and to depend critically on copolymerization.

lead articles

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Symmetry-mode decomposition of displacive distorted structures and its applications are reviewed in the light of new freely available software. The advantages of a parameterization in terms of symmetry-adapted collective coordinates are illustrated with multiple examples.

research papers

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A diffusion-equation-based optimization method for determining the global minimum of crystallographic figures of merit is described.

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For an isotropic, quasi-diluted ensemble of right cylinders of oval right section and finite height, geometric parameters are detected from the small-angle-scattering correlation function.

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Frank–Kasper structures occur in the metallurgy of alloys, the crystallography of clathrates, in soap froths and in the solution to the weak Kelvin conjecture. By using a new combinatorial enumeration algorithm, 71 new structures have been found.

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A special class of simple 24-vertex, 14-face polyhedra with four-, five- and six-edge faces has been determined in the framework of algebraic geometry.

short communications

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Agreement factors appropriate for refinements based on the ratios of intensities before and after an external perturbation is applied to a crystal are defined and compared with R factors commonly applied in static structure crystallography.

book reviews

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