The morphology of quasicrystals, incommensurate composite crystals and modulated crystals derived from the broken-bond model

A model for the surface free energy is proposed for incommensurate intergrowth compounds. Facetting of this type of aperiodic crystals is thus explained, and it is predicted that main facets common to the subsystems will have the highest morphological importance.

Theory of moiré fringes on X-ray diffraction topographs of bicrystals

The properties of moiré fringes on X-ray diffraction topographs of bicrystals are derived from the dynamical theory of X-ray diffraction and discussed for experimentally relevant cases.

X-ray diffraction moiré topography as a means to reconstruct relative displacement fields in weakly deformed bicrystals

A new method to analyse moiré fringes allows the relative displacement field between the two parts of bicrystals to be reconstructed with a strain sensitivity of 10⁻⁶ to 10⁻⁸.

Small-angle scattering by dislocations

It is shown that the small-angle scattering of X-rays or neutrons by dislocations within a deformed metal, which are partially ordered into wall-like structures, is characterized by several factors. Principally, these are associated with: (i) a single dislocation or dipole; (ii) the dislocation configuration in the plane of the wall; and (iii) the distribution of dislocations across the wall thickness.

Direct methods in protein electron crystallography – beef liver catalase in its fully hydrated form at room temperature

A direct analyis of the hydrated catalase crystal structure at room temperature is consistent with earlier studies of frozen hydrated samples by electron microscopy.

Three-wave grazing-incidence X-ray diffraction from thin crystal surface layers: determination of triplet phase invariants

Numerical calculation of the angular and spectral distributions of the intensities of the specularly diffracted waves in the case of three-wave grazing-incidence X-ray diffraction is carried out using the dynamical theory. A method of determining the value of the triplet phase invariant for thin crystal surface layers is also developed.

About new applications of parametric X-radiation for crystallography

A theoretical analysis of the parametric X-radiation (PXR) produced by the nonrelativistic electrons in an X-ray tube with a monocrystalline anode is presented.

Qu­antitative zone-axis convergent-beam electron diffraction (CBED) studies of metals. I. Structure-factor measurements

The quantitative zone-axis CBED technique ZAPMATCH is applied to low-order structure-factor measurements in nickel and copper in an attempt to resolve the debate regarding the accuracy of various experimental methods and theory calculations that have previously been applied to these materials. The extension of ZAPMATCH to the study of thermal diffuse scattering effects is also considered.

Qu­antitative zone-axis convergent-beam electron diffraction (CBED) studies of metals. II. Debye–Waller-factor measurements

The possibility of using the ZAPMATCH quantitative CBED pattern-matching technique to measure Debye–Waller factors accurately is investigated. The application of this approach to nickel and copper 〈110〉 zone-axis patterns is discussed.

X-ray phase determination by the principle of minimum charge

The minimum value of the electron density in the unit cell is proposed as an objective function for phase determination. An algorithm for maximizing this objective function, based on linear programming, finds the correct phases in numerical experiments with simulated crystalline and quasicrystalline structures.

The use of multiple-scattering data to enhance small-angle neutron scattering experiments

It is shown that SANS patterns from specimens of different thicknesses but otherwise identical not only provide information on the shape and size of the scattering entity but also give absolute values of the scattering contrast between particles responsible for SANS and the matrix. No separate calibration of the incident beam is required.

Quasiperiodic patterns generated by mixing lattices derived from a dodecahedral star and an icosahedral star

A mixing of lattices derived from a dodecahedral star and an icosahedral star is considered giving a 16 × 16 matrix for the cut-and-project method of generating 3D quasiperiodic patterns.

The joint probability distribution function of structure factors with rational indices. IV. The P1 case

Joint probability distribution functions of structure factors with rational indices are derived in P1. Phase relationships are obtained.

The joint probability distribution function of structure factors with rational indices. V. The estimates

Probabilistic formulae for estimating structure factors of half-integral index reflections are given and experimental tests are performed.

Moiré patterns in electron microscopy with atomic focuser crystals

The sharply peaked maxima of electron intensity formed at the exit face of a thin atomic focuser crystal may be used to derive the structure of a thin specimen crystal with a resolution of better than 0.04 nm.

On the geometry of a modern imaging diffractometer

A method is proposed to calibrate all the relevant instrumental parameters of a multicircle diffractometer equipped with an area detector.

Positive-definite conditions of elastic constants of two-dimensional quasicrystals with noncrystallographic symmetries

The positive-definite conditions of the elastic constants of two-dimensional quasicrystals with non-crystallographic symmetries have been derived.

A simple view of the spherical wave in dynamical theory

The well known spherical-wave results are obtained by a simple and direct calculation.

Solving crystal structures without Fourier mapping. I. Centrosymmetric case. Erratum

Erratum to Acta Cryst. (1998), A54, 273–282.

International Union of Crystallography
Report of the Executive Committee for 1997