Cover illustration: Diffuse scattering about the 002 reflection of an AlAs/GaAs superlattice grown on an oriented GaAs substrate. The in-plane and out-of plane components of the momentum transfer vector are oriented horizontally and vertically, respectively. The observed features are explained on the basis of the distorted-wave Born approximation. See Chernov et al. [Acta Cryst. (2003), A59, 551-559].
Electron momentum spectroscopy measurements and cumulant expansion many-body theoretical calculations are used to study the role of electron correlations in the ground electronic states of graphite and polycrystalline aluminium.
The Takagi–Taupin theory is synthesized with the ray–optical eikonal theory with time dependence explicitly included. Use of the dispersion surfaces in a unified space–time approach is demonstrated for diffraction under the conditions of crystal structure changes on the subpicosecond time scale. The theory is based upon microscopic electromagnetism and thus treats the spatial and temporal coordinates in the same way.
An amazingly simple structure solution algorithm is presented. It works ab initio on high-resolution data in the manner of Fourier recycling, in real space the sign of the charge density below a threshold is simply flipped.
Shapes are discussed of FFT-asymmetric units in the reciprocal space, compatible with our crystallographic FFT algorithms. An algorithm is presented for automatic generation of such shapes and points in the reciprocal space are characterized according to their isotropy subgroups. It is shown how both forward and inverse Fourier transforms can be calculated in-place.
All homogeneous sphere packings, interpenetrating sphere packings and interpenetrating sphere layers were derived which refer to the bivariant lattice complexes of the hexagonal crystal family. Examples of corresponding crystal structures are given.
It is shown how to enumerate spin point groups and spin-space-group types for quasicrystals and use them to calculate selection rules for neutron diffraction experiments. Two-dimensional octagonal quasicrystals are considered as an example.
Integral lattices (characterized by an integral metric tensor) are revealed by peaks in the frequency distribution of hexagonal and tetrahedral inorganic compounds and in the molecular form of a RNA quadruplex.