Geographic style maps for two-dimensional lattices

Continuous invariant-based maps visualize for the first time all two-dimensional lattices extracted from hundreds of thousands of known crystal structures in the Cambridge Structural Database.

Determination of the superlattice structure factor by X-ray diffraction using a temperature gradient

A method is described for determining the structure factor of a superlattice by measuring the value of the temperature gradient that provides diffraction focusing of radiation from a point source of X-rays.

Lorentz factor for time-of-flight neutron Bragg and total scattering

The Lorentz factor for the integrated intensity of time-of-flight neutron scattering is discussed in detail, including that for Bragg diffraction and total scattering. It is shown that normalization using a vanadium measurement does not, in practice, influence the existence of the Lorentz factor.

Introduction of a weighting scheme for the X-ray restrained wavefunction approach: advantages and drawbacks

A weighting scheme for the X-ray restrained/constrained wavefunction approach is proposed. Test calculations were carried out with both theoretical and experimental X-ray diffraction data to assess advantages and drawbacks of the proposed approach in the different cases.

Electron density and thermal motion of diamond at elevated temperatures

The electron densities and atomic displacement parameters of diamond are determined from 100 K to 1000 K using synchrotron powder X-ray diffraction.

A phase retrieval algorithm for triply periodic minimal surface like structures

A method to solve the crystallographic phase problem of materials with triply periodic minimal surface like structures, such as lyotropic liquid crystal bicontinuous cubic phases, is reported.

Revisited relativistic Dirac–Hartree–Fock X-ray scattering factors. I. Neutral atoms with Z = 2–118

Using relativistic wavefunctions from a B-spline Dirac–Hartree–Fock program DBSR_HF, the X-ray scattering factors and corresponding interpolating approximations in the 0–2 and 2–6 Å⁻¹ sin θ/λ ranges for all neutral atoms between He (Z = 2) and Og (Z = 118) have been re-determined. The results seem to represent an excellent compromise among all the previous studies and should (hopefully) be free of typos and inconsistencies.

Magnetic, electric and toroidal polarization modes describing the physical properties of crystals. NdFeO₃ case

A classification of the modes for magnetic, electric and toroidal polarization in crystals is proposed. The classification relies on magnetic point groups. A new notation of magnetic point groups based on the decomposition on proper rotation and generalized inversions is used.

Report of the Executive Committee for 2021