issue contents

ISSN: 2053-2733

January 2023 issue

Highlighted illustration

Cover illustration: It is possible to measure X-ray diffraction from liquid crystal phases with triply periodic minimal surface like structures, but until now there has been no effective way to reconstruct their electron density. In this issue, Oka [Acta Cryst. (2023), A79, 51–58] presents a new phase retrieval algorithm that utilizes the characteristics of liquid crystals, and shows that it is applicable to liquid crystals and mesoporous silicas with triply periodic minimal surface like structures. The image shows the electron density of the lyotropic liquid crystal bicontinuous cubic phase formed by a nonionic surfactant and water.


crystal lattices

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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.

research papers

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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.

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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.

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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.

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

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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.

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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.

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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.

international union of crystallography

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