Structural transitions in solids

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.

Crystal fingerprint space – a novel paradigm for studying crystal-structure sets

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.

Addressing chemical diversity by employing the energy landscape concept

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.

Integral modeling approach to study the phase behavior of complex solids: application to phase transitions in MgSiO₃ pyroxenes

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

Interactive visualization of quantum-chemistry data

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

Polarization effects and phase equilibria in high-energy-density polyvinyl­idene-fluoride-based polymers

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.

Mode crystallography of distorted structures

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.

Diffusion-equation method for crystallographic figure of merits

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

Geometric parameters of isotropic ensembles of right cylinders from the small-angle-scattering correlation function

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.

Space fullerenes: a computer search for new Frank–Kasper structures

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.

A special class of simple 24-vertex polyhedra and tetrahedrally coordinated structures of gas hydrates

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.

On R factors for dynamic structure crystallography

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.

Crystallography of Quasicrystals