In memory of George Sheldrick.

Pair distribution function (PDF) analysis can provide important local structure insights; however, its application in thin films is limited to those on amorphous substrates. We report a novel data processing approach and program, IsoDAT2D, which demonstrates the feasibility of using unsupervised machine learning algorithms to access PDF data from thin films on single-crystal substrates.

A new phasing method capable of solving crystal structures, from small molecules to macromolecules, is conceived and tested by a feasibility study.

Crystal Palace is a new Windows program for parametric analysis of least-squares and atomic coordination with estimated standard uncertainties. It allows the easy analysis of how crystal structures change with temperature, pressure or composition.

The structure of the α-helix is determined by a helical substructure of the 4D tube polytope with the symmetry group ±[O×D₂₀]; this substructure has a screw axis 40/11 with the angle of rotation of 99°. This polytope belongs to the family of tube polytopes with the starting groups ±1/2[O×C_2n], which determine the screw axes of the α-helices included in superhelices.

An approach is presented to calculate topological coordination numbers (tCNs) obeying the principle of coordination reciprocity from solid angles subtended by the interatomic surfaces of electron density (QTAIM) atomic domains. The tCN approach characterizes a compound's coordination situation as a set of sub-coordination scenarios with associated weights, which is considered a suitable input for future AI applications on structure–property relationships.

The variance of 1/d²_hkl positions for different lattice relaxation schemes is calculated and compared with literature formulas for anisotropic peak broadening in powder diffraction.

The report of the Executive Committee for 2023 is presented.