Impact of synchrotron X-ray radiation damage on a molecular ferroelectric crystal

The small-molecule crystallographic community has recently begun to assess the radiation damage impact of high intensity beams on samples. Bogdanov et al. [Acta Cryst. (2021), B77, 365–370] investigate the radiation damage impact on molecular ferroelectric crystal glycinium phosphite.

Unusual thermal expansion in organic molecular crystals: a rare phenomenon

A brief insight is presented into thermal expansion of organic molecular crystals with reference to the recent article by Andrew Bond [Acta Cryst. (2021), B77, 357–364].

Revisiting stacking interactions in tetra­thia­fulvalene and selected derivatives using tight-binding quantum chemical calculations and local coupled-cluster method

High-level quantum chemical calculations provide quantitative insights into the nature of intermolecular interactions in the stacking systems of tetra­thia­fulvalene and selected derivatives.

Structural reasons for the formation of multicom­ponent products and the influence of high pressure

High pressure influences the formation of the products during the photochemical reaction in crystals of (S)-(−)-1-phenyl­ethan­aminium 4-(2,4,6-tri­iso­propyl­benzoyl)­benzoate. The reason for this behaviour is the changing geometry of the molecules and their surroundings along with the change in pressure.

Crystal structure of Z-DNA in com­plex with the polyamine putrescine and potassium cations at ultra-high resolution

An ultra-high-resolution crystal structure of Z-DNA with the sequence d(CGCGCG)₂ reveals the pattern of putrescinium(2+) and K⁺ binding. The com­plete polyamine dication is visible in the electron density and assumes a position that allows for hydrogen-bond interactions with three Z-DNA duplexes. The K⁺ cation occupies a mixed K⁺/H₂O site and forms an irregular coordination sphere interacting with water molecules and the O atoms of two phosphate groups of two Z-DNA molecules, with some of the ligands present at fractional occupancy.

Site-occupancy scheme in disordered Ca₃RE₂(BO₃)₄: a dependence on rare-earth (RE) ionic radius

The rare-earth-element occupancy scheme in A₃RE₂(BO₃)₄ (A = Ca, Sr or Ba) structures shows a smooth dependence on the RE to A size ratio.

Structural effects of halogen bonding in iodo­chalcones

The structures of three iodo­chalcones are presented, highlighting the dependence of intermolecular bonding on the functionalization of their aromatic rings.

A survey of thermal expansion coefficients for organic molecular crystals in the Cambridge Structural Database

Thermal expansion coefficients are calculated for 6201 molecular crystals in the Cambridge Structural Database and the distributions of the values are assessed.

Phase transition in an organic ferroelectric: glycinium phosphite, with and without X-ray radiation damage

The effects of radiation on the formation of the polar structure of ferroelectric glycinium phosphite is discussed together with the advantages and drawbacks of synchrotron experimentation with fine temperature sampling.

Incommensurately modulated crystal structure of α′ (O′3)-type sodium cobalt oxide Na_xCoO₂ (x ∼ 0.78)

The incommensurately modulated crystal structure of α′ (O′3)-type sodium cobalt oxide Na_xCoO₂ (x ∼ 0.78) is reported.

Crystal structure of the uranyl arsenate mineral hügelite, Pb₂(UO₂)₃O₂(AsO₄)₂(H₂O)₅, revisited: a correct unit cell, twinning and hydrogen bonding

The crystal structure of the uranyl arsenate mineral hügelite is affected by twinning due to reticular merohedry (diffraction type II). This study documents, apart from the correct description of the unit cell and the nature of the twinning, the possibilities of the JANA2006 program in revealing the real nature of twinning even if using published structural data without the original reflection files.

Hydrogen-bond directionality and symmetry in [C(O)NH](N)₂P(O)-based structures: a comparison between X-ray crystallography data and neutron-normalized values, and evaluation of reliability

The N—H⋯O, H⋯O=P and H⋯O=C angles (X-ray data/neutron normalized) have been studied in nine new [C(O)NH](N)₂P(O)-based structures and 204 analogous structures retrieved from the Cambridge Structural Database. Some topics related to geometry and symmetry are addressed.

Thermal expansion and phase transformation in the rare earth di-titanate (R₂Ti₂O₇) system

The unit-cell parameter and the first temperature-dependent coefficient of thermal expansion values for nine rare earth di-titanates from 25°C to 1550°C were determined via synchrotron powder diffraction with an optical furnace, extending previous studies by 400°C–600°C. The monoclinic to orthorhombic transformation temperature in La₂Ti₂O₇ was accurately determined with both in situ powder X-ray diffraction and in situ neutron powder diffraction, giving a simpler approach to measuring this phase transformation and with higher resolution than existing single-crystal phase transformation studies.

The classification of 1D `perovskites'

The field of 1D perovskites is a growing area and has a wide variety of connectivity of octahedra. A new notation is proposed to bring more concise definition to 1D perovskites.

Structural insight from intermolecular interactions and energy framework analyses of 2-substituted 6,7,8,9-tetra­hydro-11H-pyrido[2,1-b]quinazolin-11-ones

The crystal structures of three 2-substituted 6,7,8,9-tetra­hydro-11H-pyrido[2,1-b]quinazolin-11-ones (mackinazolinone derivatives) are characterized using X-ray diffraction. Packing analyses and energy framework calculations contribute to the understanding of packing in the crystal and enable the nature of the underlying inter-molecular interactions to be delineated, while additional insight into the isolated compounds is gained from quantum chemical calculations to estimate the effect of the different substituents on the chemical reactivity of mackinazolinone.

Modelling the structural variation of quartz and germanium dioxide with temperature by means of transformed crystallographic data

A pseudocubic parameterization of the O₄ tetrahedra of quartz and its structural analogue GeO₂ at variable temperatures allows direct calculation of tetrahedral tilt angle, the microscopic order parameter of the α↔β phase transition. The crystal structures at interpolated or extrapolated temperatures can also be predicted.

Clarification of the ordering of intercalated Fe atoms in Fe_xTiS₂ and its effect on the magnetic properties

Short-range and long-range orderings of intercalated Fe atoms in Fe_xTiS₂ at the concentrations of 0.05 ≤ x ≤ 0.33 were investigated using scanning transmission electron diffraction and transmission electron diffraction. The measured magnetic properties showed a strong correlation with the ordering of Fe atoms.

High-pressure and environment effects in seleno­urea and its labile crystal field around molecules

Seleno­urea phase α is stable between 93 and 473 K, but under high-pressure up to 1.0 GPa it reveals three new forms.