Introduction to the special issue on mineralogical crystallography

A priori bond-valence and bond-length calculations in rock-forming minerals

A priori bond valences and bond lengths are calculated for a series of rock-forming minerals. Comparison of a priori and observed bond lengths allows structural strain to be assessed for those minerals.

Dehydration of microporous vanadosilicates: the case of VSH-13Na

VSH-13Na crystals represent coherent intergrowths of two polytypes (allotwinning) characterized by different orientations of the V=O apical bond in the VO₅ pyramids. The dehydration behaviour of this composite structure is presented in comparison with natural vanadosilicates.

Aravaite, Ba₂Ca₁₈(SiO₄)₆(PO₄)₃(CO₃)F₃O: modular structure and disorder of a new mineral with single and triple antiperovskite layers

The crystal structure of the new mineral aravaite was solved using synchrotron radiation and its disorder is modelled.

Copper minerals from volcanic exhalations – a unique family of natural compounds: crystal-chemical review

The crystal-chemical characterization of copper minerals (96 oxysalts, chlorides and oxides belonging to 80 structure types) formed in volcanic fumaroles is given, including data on complexes of Cu²⁺-centred polyhedra in these structures and on cationic and anionic isomorphism. The significant crystal-chemical difference between minerals formed in the hot (>473 K) and moderately hot (323–423 K) zones of fumaroles is shown; all high-temperature minerals are H-free and the Cu²⁺ cation in them exhibits a strong affinity for four- and fivefold coordination, unlike moderate-temperature fumarolic copper minerals which mainly contain OH and/or H₂O and in which Cu²⁺ shows an affinity for octahedral coordination, as it also does in Cu minerals formed in the oxidation zones of chalcogenide ores.

The atacamite family of minerals – a testbed for quantum spin liquids

Polymorphism and structural topology of the copper-bearing minerals of the atacamite family are reviewed in regard to the observed magnetic properties.

A crystallographic excursion in the extraordinary world of minerals: the case of Cu- and Ag-rich sulfosalts

The structural behavior of copper and silver in selected natural sulfosalts where these elements play a major role is reviewed.

Understanding geology through crystal engineering: coordination complexes, coordination polymers and metal–organic frameworks as minerals

The discovery of naturally occurring metal–organic framework (MOF) minerals highlights the connection between crystal engineering and mineralogy. It is shown how classification of such organic minerals rests on concepts of supramolecular chemistry, coordination chemistry and crystal engineering.

Fundamental aspects of symmetry and order parameter coupling for martensitic transition sequences in Heusler alloys

The combinations of phase transitions which occur in Heusler alloys in terms of order parameters and symmetry have been analysed using a group theoretical approach. It is shown how this approach can be applied to relevant examples.

Role of halogen-involved intermolecular inter­actions and existence of isostructurality in the crystal packing of —CF₃ and halogen (Cl or Br or I) substituted benzamides

A detailed quantitative evaluation of the nature, energetics, electrostatic contributions and topological properties of short and directional intermolecular interactions on 23 halogenated benzamides in the solid state has been performed. The occurrence of three-, two- and one-dimensional isostructurality in halogen (Cl, Br, I) substituted benzamides are also investigated.

Ab initio structure determination of [Eu₅(C₂H₄O₂)₆(CH₃CO₂)₃]_n by X-ray powder diffraction

The structure of the three-dimensional MOF compound [Eu₅(C₂H₄O₂)₆(CH₃CO₂)₃]_n was solved ab initio from synchrotron X-ray powder diffraction. With pore volumes of 82 ų, the structure is similar to those usually observed in zeolites, which makes it suitable for gas storage.

Crystal and solution structures of calcium complexes relevant to problematic waste disposal: calcium gluconate and calcium isosaccharinate

The crystal structures of calcium D-gluconate and calcium α-D-isosaccharinate nave been determined, the latter using a synchrotron source, and found to be coordination polymers. Computational studies complement the structure determinations.

Cocrystals with tunable luminescence colour self-assembled by a predictable method

The σ-hole and π-hole bonding interactions in cocrystals consisting of acenaphthene and haloperfluorobenzenes can be predicted before assembling them by using the maximum surface electrostatic potential difference between the σ-hole and the π-hole in the bonding donor molecules. Thus, fluorescence, delayed fluorescence and phospho­rescence properties of the cocrystals can be estimated.

Crystal packing and theoretical analysis of halogen- and hydrogen-bonded hydrazones from pharmaceuticals. Evidence of type I and II halogen bonds in extended chains of di­chloro­methane

Supramolecular assemblies of halogenated and hydroxyl hydrazones derived from pharmaceuticals are governed by I⋯N and I⋯π halogen bonds or O—H⋯N hydrogen bonds. An unexpected linear arrangement of clathrated di­chloro­methane molecules bound through type I and II halogen bonds is observed. Theoretical calculations support the crystallographic study.

ZnO/ZnS (hetero)structures: ab initio investigations of polytypic behavior of mixed ZnO and ZnS compounds

The main topic of this study is newly discovered ZnO/ZnS polytypes, which provide alternative structural arrangements of ZnO/ZnS compounds. In particular, pristine ZnO and ZnS compounds and mixed ZnO_1–xS_x compounds (x = 0.20, 0.25, 0.33, 0.50, 0.60, 0.66 and 0.75) have been investigated. All calculations have been performed at ab initio level using density functional theory–local density approximation and hybrid Heyd–Scuseria–Ernzerhof functionals.

The inverse perovskite BaLiF₃: single-crystal neutron diffraction and analyses of potential ion pathways

High-temperature neutron diffraction has been performed on a single crystal of oxide-containing BaLiF₃. Analyses of topology and bond-valence site energies at 636.2°C show it to be a vacancy-dependent anion conductor with an estimated migration barrier of ∼0.64 eV.

Structure factors and charge-density study of diamond at 800 K

The structure factors of diamond at 800 K at sin θ/λ ≤ 2.2 Å⁻¹ were determined from multiple overlaid powder profiles. Data correction was essential to extract the Bragg intensities of the weak reflections. The quality of the final charge density determined at 800 K was nearly comparable with that of room-temperature data.

Positive and negative monoclinic deformation of corundum-type trigonal crystal structures of M₂O₃ metal oxides

Synchrotron radiation powder diffraction studies of selected M₂O₃ oxides with nominal corundum-type trigonal structure show two types of monoclinic distortions at ambient conditions. `Positive' monoclinic distortion in Ti<sub>2</sub>O<sub>3</sub>, V<sub>2</sub>O<sub>3</sub>, Cr<sub>2</sub>O<sub>3</sub> and `negative' monoclinic distortion in Al₂O₃, α-Fe₂O₃ are discussed in the context of a possible metal–metal bond as suggested in the literature.

Martensitic transformation, electronic structure and magnetism in D0₃-ordered Heusler Mn₃Z (Z = B, Al, Ga, Ge, Sb) alloys

Mn₃Al shows great potential for application as a ferromagnetic shape memory alloy. Moreover, not only did the martensitic transformation occur in Mn₃Al, it was also observed in similar D0₃-ordered Mn₃Z (Z = B, Ga, Ge, Sb) compounds.

Electronic structure of two isostructural `paddle-wheel' complexes: a comparative study

The experimental electron-density distribution in two isostructural complexes, tetra­kis(μ₂-acetato)di­aquadicopper(II) [H₂OCu(ac)₂Cu(ac)₂H₂O] and tetra­kis(μ₂-acetato)di­aquadichromium(II) [H₂OCr(ac)₂Cr(ac)₂H₂O], has been studied and compared.

Charge density and electrostatic potential of hepatitis C anti-viral agent andrographolide: an experimental and theoretical study

The experimentally derived electrostatic properties using the multipole model of Andrographolide reveal the reactive nature of this molecule in the biological environment.

Theoretical study of charge-transport and optical properties of indeno[1,2-b]fluorene-6,12-dione-based semiconducting materials

The conducting and optical properties of a series of indeno[1,2-b]fluorene-6,12-dione (IFD)-based molecules have been systematically studied and the influences of butyl, butyl­thio and di­butyl­amino substituents on reorganization energies, intermolecular electronic couplings and charge injection barriers of IFD have been discussed.

Copper–lead selenite bromides: a new large family of compounds partly having Cu²⁺ substructures derivable from kagome nets

Extensive experiments in the Pb–Cu–Se–O–Br system at 400°C yielded single crystals of nine new compounds, all but one exhibiting new complex layered or open-framework architectures, organized via the host–guest principle. A remarkable feature of half of the reported compounds is the presence of tetrahedral (Cu²⁺)₄ complexes with arrangements derivable from a kagome network.

Structural, energetic and spectroscopic studies of new luminescent complexes based on 2-(2′-hy­droxy­phenyl)­imidazo[1,2-a]pyridines and 1,2-phenyl­ene­diboronic acid

Three new blue-luminescent complexes of selected 2-(2′-hy­droxy­phenyl)­imidazo[1,2-a]pyridines and 1,2-phenyl­ene­diboronic acid are reported and characterized structurally, spectroscopically and computationally, and discussed within the literature context.

Triamterene–furosemide salt: structural aspects and physicochemical evaluation

A novel drug–drug salt of furosemide (a rapid-acting diuretic) with triamterene (a potassium-sparing diuretic) was successfully synthesized. This dual pharmaceutical salt was comprehensively characterized using single-crystal/powder X-ray diffraction, thermal analysis and vibrational spectroscopy.

Octahedral tilting in the tungsten bronzes. Addendum.

Further investigation of the tilting of corner-connected octahedra in the tetragonal tungsten bronzes has revealed possible structures not identified in our earlier work.