X-ray constrained spin-coupled technique: theoretical details and further assessment of the method

A new method that extends the Jayatilaka X-ray constrained wavefunction approach in the framework of the spin-coupled technique of the valence bond theory is presented. The proposed strategy enables the extraction of traditional chemical information (e.g. weights of resonance structures) from experimental X-ray diffraction data without imposing constraints a priori or performing further analyses a posteriori.

Crystallography of three-dimensional fluid flows with chirality in hexagonal cases

Magnetic groups are applied to three-dimensional fluid flows with chirality, which are called Beltrami flows. Eight Beltrami flows are derived and studied using Wyckoff positions. The crystal-like structures of their tube-like surfaces, called invariant tori, are numerically observed.

Perfect colorings of patterns with multiple orbits

Perfect colorings of patterns with multiple orbits were characterized, with a focus on colorings where the orbits share colors. These results were then applied to construct perfect and non-perfect colorings of various symmetrical objects.

A universal algorithm for finding the shortest distance between systems of points

A universal and effective algorithm is proposed for geometrical comparison of abstract sets of n points in Euclidean space. Applications of the algorithm for comparison of both finite (ligands) and periodic (nets) chemical objects are considered.

Measurement and alleviation of subsurface damage in a thick-crystal neutron interferometer

The alleviation of subsurface machining damage in a thick-crystal neutron interferometer is investigated by testing the interferometer throughout an annealing and chemical etching post-fabrication process. Spatially varying Bragg-plane angular misalignments between diffracting components of the interferometer are lessened from 10⁻⁵ rad to less than 10⁻⁹ rad.

X-ray interference fringes from a weakly bent plane-parallel crystal with negative strain gradient

In the waves emitted from the entrance, back and lateral surfaces of a very weakly bent plane-parallel perfect crystal with negative strain gradient, X-ray interference fringes between two refracted beams with different hyperbolic trajectories were observed when the strain was very weak, of the order of 10⁻⁷.

Bayesian machine learning improves single-wavelength anomalous diffraction phasing

The a posteriori probability densities of anomalous structure-factor amplitude differences were estimated by the Markov chain Monte Carlo machine-learning method. The model incorporated the correlation between the different Bijvoet pairs and the improved estimates were shown to be beneficial for SAD phasing.

Relativistic correction of atomic scattering factors for high-energy electron diffraction

Relativistic electron diffraction depends on linear and quadratic terms in the electric potential, the latter being neglected in the frequently used relativistically corrected Schrödinger equation. Conventional tabulations for electron scattering and its large-angle extrapolations can be amended in closed form by a universal correction based on the screened Coulomb potential squared.

A parameter-free double-shear theory for lath martensite

In analogy to the original phenomenological theory of martensite crystallography, a double-shear theory for lath martensite is proposed which chooses the shearing systems as those that are macroscopically equivalent to double twinning. Using only the additional assumptions of overall small shape strain magnitude and a condition of maximal compatibility, this approach naturally gives rise to {5 5 7}_γ habit planes and orientation relationships close to the Kurdjumov–Sachs model.

Data-driven approach for synchrotron X-ray Laue microdiffraction scan analysis

A novel data-driven approach for synchrotron Laue X-ray microdiffraction scans is presented based on machine learning techniques.

Verification of the de Wolff hypothesis concerning the symmetry of β-MnO₂

The de Wolff hypothesis concerning the orthorhombic symmetry of some rutile-type compounds is quantitatively confirmed for β-MnO₂ and MnF₂.

Elastic propagation of fast electron vortices through amorphous materials

This article describes the scattering behavior of electron vortices inside amorphous samples. It focuses on the vortex purity, net angular momentum transfer, and statistical variations due to random beam and atom positions.

Prices of IUCr journals

Berry Phases in Electronic Structure Theory. Electric Polarization, Orbital Magnetization and Topological Insulators

Islamic Geometric Patterns: Their Historical Development and Traditional Methods of Construction