Nifedipine (NIF) molecules (L-type calcium channel antagonists) pack in solvated structures showing strikingly similar patterns, see Jones et al. [Acta Cryst. (2023), B79, 164–175]. How much do molecular shapes, such as the NIF molecule which resembles the letter T, matter in their associations in crystals?

Pseudoatom databanks, collections of parameters from the multipole model of electron densities for various atom types, are used to replace the Independent Atom Model with the more accurate Transferable Aspherical Atom Model (TAAM) in crystal structure refinements. The databanks are also employed to reconstruct the electron density of a molecule, crystal or biomacromolecular complex in a fast yet accurate way and compute various properties such as the energy of electrostatic interactions, for example. A even faster but similarly accurate model for estimations of electrostatic energy exists called aug-PROmol [Bojarowski, Kumar & Dominiak (2016). ChemPhysChem, 17, 2455–2460]. A model analogous to aug-PROmol cannot be built from the current pseudoatom databanks, as they perform badly when truncated to the monopole level. Here, new strategies for multipole model refinements were sought, leading to better parametrization at the monopole level. This would allow the creation of a pseudoatom databank in a single route of model parametrization, which would be suitable for both crystal structure refinement and rapid electrostatic energy calculations. Here it is shown that the cumulative approach to multipole model refinements, as opposed to simultaneous or iterative refinements of all multipole model parameters (Pv, κ, Plm, κ′), leads to substantially different models of electron density. Cumulative refinement of two blocks of parameters, the first with Pv and κ and then the second with Plm and κ′, leads to the Pvκ|Plmκ′ model having promising properties. The Pvκ|Plmκ′ model is as good as the University at Buffalo DataBank (UBDB) in X-ray structure TAAM refinements and electrostatic energy estimations, especially for less polar molecules. When truncated to the monopole level, the Pvκ model has a chance to replace aug-PROmol in fast yet accurate electrostatics energy calculations, although some improvements in κ parametrization for polar functional groups are still needed. The Pvκ model is also a source of point charges which behave similarly to restrained electrostatic potential (RESP) charges in electrostatic interaction energy estimations.

A triple salt of decavanadate, V10O286−, containing mixed organic guanylurea (diaminomethylideneurea cation, HGU+) and metforminium(2+) (H2Met2+) cations and hydronium (H3O+) cations, has been synthesized by heating metformin hydrochloride, picolinic acid, and sodium metavanadate in aqueous solution at pH 4 and 333 K followed by maintaining the solution at 300 K overnight to give an orange crystalline product. As commonly observed, the V10O286− anion lies on an inversion center. Charge is balanced by two H2Met2+ dications and two monocations, one HGU+ and one H3O+, substitutionally disordered about another inversion center. The HGU+ cation is further positionally disordered by rotation of 26.3 (4)° about an axis approximately along the direction of the three essentially collinear N atoms of the cation, thereby hydrogen bonding to two adjacent rows of cluster O atoms running diagonally across the equatorial plane of the V10O286− anion. The highly concerted nature of the HGU+…cluster interaction in each orientation suggests a synthon that likely preexisted in solution and perhaps, along with heat, contributes to the degradation of the metformin to HGU+. The structure of the salt exhibits a complex charge-stabilized hydrogen-bonded network involving extended C44(8) chains of the water molecules and the H2Met2+ cations linking the chains into two-dimensional sheets parallel to the bc plane, and V10O286− anions linking those sheets into a three-dimensional structure through Ow—H…O, N—H…O and C—H…O intermolecular interactions. The disordered HGU+ cation and the H3O+ cation occupy spaces with excess volume in the three-dimensional network structure.

This work is devoted to an investigation of elemental composition, crystal structure and thermal expansion of natural oxoborate azoproite from the Tazheran massif (Siberia, Russia) in the temperature range 5–1650 K. Elemental composition was determined by energy-dispersive X-ray spectroscopy (EDX). Its empirical formula based on five oxygen atoms is (Mg1.81Fe2+0.19)∑2.00(Fe3+0.36Ti0.26Mg0.26Al0.12)∑1.00O2(BO3). Local environment, oxidation states and ratio of Fe atoms are determined using Mössbauer spectroscopy and compared with EDX and single-crystal X-ray diffraction (SCXRD) data. A refinement of the crystal structure from SCXRD data collected at 293 K was provided for the first time. The structure could be described both in terms of cation- and anion-centered polyhedra. It is composed of vertex- and edge-sharing metal–oxygen [MO6]n− octahedra that form extended zigzag chains along the a axis building up a framework with the [BO3]3− triangles located in its distorted trigonal channels. From the other point of view, there are double chains consisting of oxocentred [OM4]n+ tetrahedra and [OM5]n+ tetragonal pyramids forming six-membered rings with the triangles in its cavities. Four non-equivalent Mn+ sites are occupied by cations as follows: M(1) (2a) and M(2) (2d) – Mg, M(3) (4g) – Mg and Fe2+, M(4) (4h) – Fe3+, Ti4+, Mg and Al3+. According to differential scanning calorimetry, low- and high-temperature powder X-ray diffraction (LT- and HT-XRD) data, Mössbauer spectroscopy and magnetometry data (5 ≤ T ≤ 1650 K), there are no phase transitions obtained in the temperature range investigated. However, some anomalies in temperature dependencies of unit-cell parameters caused by a partial Fe2+ → Fe3+ oxidation are found in the range 873–1173 K. Azoproite melts at a temperature higher than 1600 K. Eigenvalues of the thermal expansion tensor are calculated for the oxoborate and thermal expansion is described in comparison with its crystal structure.

Three new 5-dimethylaminomethylidene-4-phenylamino-1,3-thiazol-2(5H)-ones with an hydroxyl group in the ortho, meta and para positions on the phenyl ring were synthesized in order to deduce the structural changes occurring on prototropic tautomerism of the amidine system. The existence of all the title compounds solely in the amino tautomeric form has been established in the solid and liquid (dimethyl sulfoxide solution) phases. The title compounds are analyzed from the point of view of the electronic effects and conformational freedom of their molecules. The intermolecular interactions in the crystals and their supramolecular architecture are highlighted.

Single crystals of [K1–x(NH4)x]3H(SO4)2 (x ≥ 0.57) grown in the K3H(SO4)2–(NH4)3H(SO4)2–H2O water–salt system are studied. The atomic structure including H atoms was determined at room temperature using X-ray structural analysis. [K1–x(NH4)x]3H(SO4)2 (x ≥ 0.57) crystals have trigonal symmetry and disordered hydrogen-bond networks at ambient conditions similar to the high-temperature phases of K3H(SO4)2, (NH4)3H(SO4)2 and other superprotonic compounds M3H(AO4)2. Impedance measurements performed on single crystals show high values of conductivity characteristic for superprotonic phases. Using the methods of impedance spectroscopy and atomic force microscopy, a significant anisotropy of the conductivity of crystals has been detected. It was also shown that there is a qualitative correlation of bulk and local conductivity measured for samples of the same composition and orientation at room temperature, which is due to the peculiarities of their crystal structure.

A novel approach is proposed for the description of possible reconstructive solid-state transformations, which is based on the analysis of topological properties of atomic periodic nets and relations between their subnets and supernets. The concept of a region of solid-state reaction that is the free space confined by a tile of the net tiling is introduced. These regions (tiles) form the reaction zone around a given atom A thus unambiguously determining the neighboring atoms that can interact with A during the transformation. The reaction zone is independent of the geometry of the crystal structure and is determined only by topological properties of the tiles. The proposed approach enables one to drastically decrease the number of trial structures when modeling phase transitions in solid state or generating new crystal substances. All crystal structures which are topologically similar to a given structure can be found by the analysis of its topological vicinity in the configuration space. Our approach predicts amorphization of the phase after the transition as well as possible single-crystal-to-single-crystal transformations. This approach is applied to generate 72 new carbon allotropes from the initial experimentally determined crystalline carbon structures and to reveal four allotropes, whose hardness is close to diamond. Using the tiling model it is shown that three of them are structurally similar to other superhard carbon allotropes, M-carbon and W-carbon.

The structural stability of hexagonal tungsten mononitride (WN) has been studied combining scanning transmission electron microscopy and first-principles calculations. The results show that the WC-type WN with vacancies of 6∼8 at% is more stable than the previously proposed MnP-type and NiAs-type structures. Due to the larger vibrational entropy of the WC-type WN, the vacancy concentration required to stabilize the WC-type structure is lower at high temperatures. The results demonstrate the importance of vacancies and configurational and vibrational entropies in the structural stability of compounds synthesized at high temperatures.

A short commentary is given on a recent paper by Carolyn Pratt Brock [Acta Cryst. B78, 576–588] which discusses the occurrences of approximate symmetries in space group P1.

Solar thermochemical hydrogen production (STCH) via redox-active metal oxides is an approach for direct solar-driven hydrogen generation typically using a high-temperature redox cycle involving refractory oxides and steam. Typical cycles involve high-temperature reduction of oxides to form oxygen vacancies, followed by lower temperature reaction between oxygen vacancies and steam where the oxide is re-oxidized and the steam is reduced to hydrogen. Only a few materials have demonstrated reversible cycling under the typically harsh STCH conditions (e.g. 1500°C reduction, 900°C re-oxidation) and critical questions remain on the true reversibility of non-stoichiometric multi-cation oxide systems, significantly hampered by the lack of single-phase samples for these material systems. To date, most STCH processes have relied on CeO2 as a benchmark active material, but more recently, the 12R phase of BaCe0.25Mn0.75O3 (BCM) has demonstrated greater hydrogen-generation potential at lower peak temperatures. However, previous reports of 12R-BCM have included large fractions, > 10 wt%, of secondary phases, which complicate analysis of the stability and performance. A comprehensive understanding of the redox mechanism and reversibility of the process in BCM can only be achieved with nearly single-phase samples which, to date, have been difficult to produce. Here two approaches to BCM synthesis are reported: solid state and sol–gel-based routes. It is demonstrated that both routes can be tuned to produce the 12R structure with > 97 wt% yield when annealed ≥1450°C. Herein synchrotron-based diffraction measurements of rhombohedral 12R-BCM enabled characterization of the anisotropy between thermal expansion along the c-axis and within the ab plane. The impact of high-temperature redox cycling on the stability and phase fraction of the 12R-BCM polytype was also investigated. These results offer two viable routes for synthesis of high-purity 12R-BCM critically needed for evaluating the efficacy of BCM as a STCH material and validate its ability to split water at lower temperatures over extended numbers of redox cycles.

Vanadium–tellurite glasses, tetragonal TeO2 and orthorhombic V2O5 crystalline samples were characterized for their atomic structure properties by synchrotron X-ray diffraction, pair distribution function analysis, reverse Monte Carlo simulations (RMC) and Rietveld analysis. The pair correlation function, G(r), of V2O5 shows the first peak at 1.61 Å. G(r) of TeO2 shows three peaks at 1.57, 2.13 and 2.88 Å due to Te–O linkages of three different lengths, whereas the Te–Te atomic pair correlation shows a peak at 3.85 Å. The average coordination number of V with O in crystalline V2O5 is 4.39 while that of Te with O in crystalline TeO2 is 3.71. G(r) of the vanadium tellurite glass shows the first peak at 1.90 Å due to overlapping Te–O and V–O atomic pair correlations. The RMC analysis on diffraction data of glasses found that the V–O coordination number is in the range 5.27–5.59 and the Te–O coordination number is 5.39–5.67. However, it is found that these coordination numbers cannot be clearly defined due to short-range disorder.

Experimental charge density analysis is conducted on the coordination compound tetraaquabis(hydrogenmaleato)nickel(II), which exhibits a short intramolecular hydrogen bond. Through topological analysis, the nature of Ni—O bonds is concluded to be intermediate between ionic and covalent, but mainly presenting an ionic character, while the short hydrogen bond is classified as covalent in nature. The compound was also analysed after Hirshfeld atom refinement performed using NoSpherA2. A topological analysis was conducted on the molecular wavefunction and the results are compared with those obtained from experiment. In general, there is good agreement between the refinements, and the chemical bonds involving H atoms are in better agreement with what is expected from neutron data after HAR than they are after multipole refinement.

A method for the visualization of noncovalent interactions using examples of the conformational polymorphs of four organic compounds: 2-(phenylamino)nicotinic, 2-(3-chloro-2-methylphenylamino)nicotinic, N-(3-chloro-2-methylphenyl)anthranilic and 2-(methylphenylamino)nicotinic acids is examined. The changes in noncovalent contacts are plotted against the angle between the planes of aromatic rings allowing a visual representation of conformational adjustment of molecules as well as packing features of crystal structures. According to the k–Φ criterion, the studied structures represent conformational polymorphs. Different types of hydrogen bonding are discussed within the framework of the method of visualization and molecular Voronoi–Dirichlet polyhedra. Good correlations are found between calculated and experimental data for several cases, such as the agreement between π stacking and polymorphic transition temperatures as well as between the area of a contact and the energy of conjugation. Also, an attempt has been made to assess the relative contributions of conformational and packing polymorphism in the formation of polymorphs.

Compounds with the general formula Ln3+(SeO3)(HSeO3)·2H2O, where Ln = Sm3+, Tb3+, Nd3+ and Lu3+, are characterized by orthorhombic symmetry with space group P212121 and unit-cell parameters in the ranges a ∼ 6.473–6.999, b ∼ 6.845–7.101, c ∼ 16.242–16.426 Å. Light-purple irregularly shaped crystals of a new monoclinic polytype of neodymium selenite Nd(SeO3)(HSeO3)·2H2O have been obtained during a mild-condition hydrothermal synthesis. The monoclinic unit-cell parameters are: a = 7.0815 (2), b = 6.6996 (2), c = 16.7734 (5) Å, β = 101.256 (1)°, V = 780.48 (6) Å3; space group P21/c. The crystal structures of Nd(SeO3)(HSeO3)·2H2O polymorphs show order–disorder (OD) character and can be described using the same OD groupoid family, more precisely a family of OD structures built up from two kinds of non-polar layers (category IV). The first monoclinic maximum degree order (MDO) structure (MDO1-polytype) with space group P21/c can be obtained when the inversion centre is active in the L2n-type layers, while the second MDO structure (MDO2-polytype) is orthorhombic with space group P212121 and can be obtained when the [21--] operation is active in the L2n-type layers. The structural complexity parameters and DFT calculations of both polytypes show that the polytype structures are extremely close energy-wise and almost equally viable from the point of total energy of the structure.

In recent years, significant advances have been made in the precise control of the physical properties of metal–organic frameworks (MOFs) via the linker-modulated method in which modulators compete with linkers and impose kinetic limitations through crystal growth. In this regard, the structure of a new barium–organic framework [Ba(H2BTC)2(H2O)4]n, BaBTC (BTC = 1,3,5-benzene tricarboxylic acid) is introduced, which allows the competitive coordination strategy and growth orientation of an alkaline-earth metal–organic framework (AEMOF) to be probed without sacrificing phase purity, porosity and crystallinity. The modulator effect of an assortment of amino acids on the particle size and morphology of BaBTC is investigated. Additionally, another new MOF [Ba(BTC)2(H2O)3]n.nH2O, BaBTC-2, is synthesized through a change in the ligand concentration. This work gives a successful example of a modulation method for AEMOF synthesis by amino acids that may contribute towards targeting future avenues of nanomaterial synthesis.

The synthesis and characterization of a first salt-inclusion aluminophosphate oxocuprate, (Na,Li)3(Cl,OH)[Cu3OAl(PO4)3], obtained as single crystals, is reported. A novel phase, with a strongly pseudo-orthorhombic structure, is described as a monoclinic crystal structure established by the study of a pseudomerohedric microtwin. It was investigated using scanning electron microscopy, microprobe analysis and low-temperature X-ray diffraction. The composite crystal structure represents an original framework assembled from Cu-centered polyhedra, AlO6 octahedra and PO4 tetrahedra with channels, which incorporate the Na/Li salt component [(Na,Li)3(Cl,OH)]2+ that ensures electroneutrality of the compound. Layers of strongly corrugated chains of Cu-centered octahedra with shared edges and linked by PO4 tetrahedra are shown to be topologically identical with the layers also built from Cu-centered polyhedra and AsO4/VO4 tetrahedra forming the crystal structure of a fumarolic mineral aleutite, (M0.5Cl)[Cu5O2(AsO4)(VO4)] [Siidra et al. (2019). MinMag, 83, 847–853]. `Sawtooth chains' and pairs of Cu-centered octahedra inherent in the title structure may be of interest in solid-state physics, engaging studies in the field of low-dimensional and frustrated magnetism.

Single crystal specimens of apatite-type compounds Ca5(VO4)3Cl and Ca4.78 (1)Na0.22(PO4)3Cl0.78 were prepared with a flux-growth technique and their structures were examined with single-crystal X-ray diffraction. The anion channel is defined by a face-sharing array of nearly regular Ca octahedra, which run along c, together with flat O3 trigonal antiprisms that are concentric with the Ca octahedra and highly oblate in [001]. The position of the channel anion in Ca5(VO4)3Cl is split into two at [0, 0, ±0.1691 (6)] with half occupancies. Dynamic disorder among these two positions is suggested from a saddle-shaped electron density distribution through the Ca regular triangle, i.e. the shared face of the Ca octahedra at z = ¼. The position of Cl− was too close to Ca2+ under bond-valence consideration. This is due to repulsion on Cl− from the flat O3 trigonal antiprism which is located at z = 0, namely, in between pairs of split Cl site positions. Ca4.78 (1)Na0.22(PO4)3Cl0.78 crystallizes as a disordered hexagonal structure in which the crystallographic pattern is not an intermediate state but a projection of two distinct halves of the monoclinic pattern [doubled in b; Mackie, Elliot & Young (1972). Acta Cryst. B28, 1840–1848] in one hexagonal cell. In spite of quite different environments, the bond-valence sums for Cl− in these structures are large and similar to each other. The repulsion between O2− and Cl− and a demand for keeping Ca2+ and Cl− apart are balanced at the positions where bond-valence sums for Cl− are around 1.2.

The metallic components are manufactured through several thermomechanical processes. Each selected procedure has multiple targets. The first target is to obtain the required dimensional criteria and second, to achieve the ideal mechanical response toward the application. This is currently accomplished through years of knowhow combined with an academic background of materials science and engineering. Since metals are polycrystalline materials, the several rotations of the crystals, the preferred orientation also known as texture, and their interactions, are crucial characteristics that are directly correlated to the final response of the material, and one could apprehend its thermomechanical prehistory as well as predict is behavior. Different atomic arrangements act differently texture-wise therefore in the current review article, the evolution of the microstructure and the crystallographic texture through the thermomechanically rolling process especially of Al alloys for packaging applications is analyzed. The crystallographic texture evolution in 3xxx Al alloys in different processing routes is presented and compared to the anisotropic effects occurring during deep drawing. The earing phenomena in Al alloys are correlated to the produced texture and therefore their understanding is crucial in order to highlight the importance of texture control throughout the thermomechanical process.