Introducing the special issue on current research in crystal growth and related characterization

The special issue on crystal growth and related characterization is introduced. The articles were originally published in recent regular issues of Acta Crystallographica Section B.

Structural and magnetic investigations of the Weyl semimetal family CeAlSi_1–xGe_x

A systematic investigation is reported of the structural and magnetic evolution in the CeAlSi_1–xGe_x series, combining X-ray and neutron diffraction with magnetization measurements on polycrystalline samples and single crystals. Chemical substitution leads to a continuous lattice expansion and a suppression of the ferromagnetic ordering temperature without a structural phase transition, revealing a crossover towards antiferromagnetic behaviour and establishing CeAlSi_1–xGe_x as a model system for compositionally tuned magnetism in noncentrosymmetric materials.

Investigating the impact of molybdenum content on the room-temperature optical properties of Li₂WO₄ crystals grown by low-thermal-gradient Czochralski technique

It is shown that even 1.25% of molybdenum in tungstate structure leads to significant decrease in X-ray luminescence intensity. On the other hand, 1.25% molybdenum doping shifts photoluminescence emission to longer wavelengths, the shift increasing with Mo concentration increasing to 5%, without decreasing photoluminescence intensity.

Maus's salts: an old family of iron sulfates with possible magnetic frustration

Structural investigations into Maus's salt derivatives reveal great sensitivity toward alkali metal and cocrystallized water content. Magnetic properties of the Maus's salt iron trimer are explored.

Silicon allotropes by large-volume high-pressure techniques: crystal growth mechanisms, phase diagrams and hexagonal nanostructured Si-6H by in situ X-ray diffraction and computational methods

In situ X-ray diffraction is used for exploring Si crystallography and for studying phase-transformation mechanisms in elemental Si and Na–Si systems. We present original results of hexagonal silicon, Si-6H and a critical analysis of the past-decade discoveries of silicon Si-4H and Si₂₄ using large-volume high-pressure techniques.

Unraveling the symmetry of Al₅C₃N

From experimental and theoretical techniques employed in this thorough reexamination of the structure of Al₅C₃N, the crystal structure is better described in centrosymmetric space group P6₃/mmc (No. 194) rather than in the previously reported noncentrosymmetric space group P6₃mc (No. 186).

Re-refinement of the structure of the planar hexagonal phase of ZnO nanocrystals

The planar hexagonal phase of ZnO is significant for understanding ferroelectricity in this class of materials, and it is well established for ZnO in layered systems. Previously it has been reported as freestanding nanocrystals, but the fitted unit-cell parameters differed from predictions by up to 16%; we resolve this anomaly to provide fundamental understanding of ferroelectric switching.

Form (III) of artemisinin: discovery and crystallographic characterization of a new high-pressure polymorph

The polymorphic behaviour of the three forms of artemisinin was investigated using single-crystal X-ray diffraction in a diamond anvil cell, with notable observation of a pressure-induced phase transition from form (II) to form (III).

α-L-Tyrosine under high pressure: validation of phase transitions and a curious similarity with L-alanine

The effect of hydro­static compression on the crystal structure of α-L-tyrosine was studied and compared with that reported previously for other amino acids, in particular, for structurally related L-alanine.

Structural modification of functionalized carbazoles: from Z′ = 1 to Z′ = 6

The crystal structure of a 2,3,9,9a-tetra­hydro-1H-carbazole in the space group Ia is reported, showing Z′ = 6 and approximate Fdd2 symmetry, and compared to the low Z′ crystal structures of two closely related congeners.

Incommensurate structure of AlPO₄-5 and its stability

The incommensurately modulated structure of AlPO₄-5 was elucidated by single-crystal X-ray diffraction, revealing correlated rotational displacements of AlO₄ and PO₄ tetrahedra.

L-threo-D-galacto-Octitol: a curious non-classical order–disorder polytype with an 88 Å axis

The sugar alcohol L-threo-D-galacto-octitol crystallizes in a structure with P4₃2₁2 pseudo-symmetry and a highly elongated unit cell (c ≈ 88 Å). In distinct layers of the structure, symmetry is broken by an asymmetric hydrogen-bonding network leading to polytypism, which is discussed in the framework of order–disorder theory.

AB₂X₄ spinel structures: similarity and differences between the centrosymmetric, Fd3m, and non-centrosymmetric, F4₁32, space groups

Both centrosymmetric, Fd3m, and non-centrosymmetric, F4₁32, space groups cannot be distinguished in solving, refining and describing AB₂X₄ spinel structures in the harmonic approximation. They can be distinguished only by using the third-order tensor approximation of anisotropic displacement parameters.