Numerically stable algorithms for the computation of reduced unit cells

Two numerically stable cell reduction algorithms are introduced.

Topological density of nets: a direct calculation

An expression for the topological density of n-dimensional nets is derived from geometrical characteristics associated with their quotient graph.

On a fast calculation of structure factors at a subatomic resolution

The computational complexity of the structure-factor calculation through an intermediate density generation and its Fourier transform have been studied for the subatomic resolution range. Parameters of the method are suggested that minimize the time of the calculations.

Ultra-high-angle double-crystal X-ray diffrac­tometry (U-HADOX) for determining a change in the lattice spacing: experiment

The characteristics of ultra-high-angle double-crystal X-ray diffractometry at Bragg angle 89.5° is described together with an application for determining the linear thermal-expansion coefficient of silicon.

A Fourier optics approach to the dynamical theory of X-ray diffraction – perfect crystals

The paper presents a formalism, based on Takagi's equations and Fourier optics, applicable to the dynamics of X-rays in crystals. The analogy between the dynamics of X-rays and that of two-level quantum systems is exploited to describe X-ray propagation in crystals from a new point of view.

γ-ray and neutron diffraction studies of CoF₂: magnetostriction, electron density and magnetic moments

Paramagnetic antiferromagnetic CoF₂ has been studied by various diffraction techniques. Detailed information on the structural, electronic and magnetic characteristics is presented.

Dispersion corrections of the copper K edge measured by Fresnel diffraction

Dispersion corrections to the atomic scattering factors for the copper K edge have been measured by a new technique, Fresnel diffraction. The results are comparable to those measured by other techniques.

Phase-dependent polarization aspects of three-wave X-ray diffraction: an iterative Born approximation

The iterative Born approximation is derived for analysis of the dependence of three-wave dynamical X-ray diffraction profiles on the polarization state of a linearly polarized incident wave. General conditions of the phase sensitivity, the asymmetries of diffraction profiles, as well as the prediction of new diffraction features are obtained from this approximation and compared with direct dynamical calculations.

First-principles calculations as a tool for structure validation in electron crystallography

The metal-rich structures of Ti₁₁Se₄ and Ti₄₅Se₁₆, which were determined by electron crystallography, have been validated by means of total energy calculations within the non-local density functional theory (program CASTEP). The calculations proved the correctness of the structures and yielded slightly improved lattice parameters and atomic coordinates for both compounds.

Ab initio crystal structure determination using X-ray fluorescence holography for different noise levels: numerical simulation and analysis

The capability of the ab initio structure determination method using X-ray fluorescence holography is proven and it is shown that it does not heavily depend on the holography pattern noise.

Applied geminography – symmetry analysis of twinned crystals and definition of twinning by reticular polyholohedry

The symmetry of twins is revised in terms of the lattice point and translational symmetry and the new category of reticular polyholohedry is introduced. Examples from the literature are critically revisited.

Nominations for the Ewald Prize

Notes for authors 2004