Search

The information-entropy measures of the complexity of nets are proposed that take into consideration both the vertices and edges of nets. The parameters quantify the amount of Shannon information per element (vertex or edge) and per the translationally independent parts of the nets. The nets can be classified according to their complexity into very simple (0–20 bit per cell), simple (20–100 bit per cell), intermediate (100–500 bit per cell), complex (500–1000 bit per cell), and very complex (>1000 bit per cell). The information entropies for 1936 3D nets were calculated and analysed, showing that the simplest (information-poor) nets possess the lowest transitivities. The majority of the most common nets in metal–organic frameworks (MOFs) are the simplest nets within their respective categories (i.e. among the nets with the same coordination of vertices). Since the information is directly related to entropy, which is understood as a statistical parameter, the preference of the simplest nets in MOFs is at least in part governed by their low information contents and high configurational entropies. [ABSTRACT FROM AUTHOR]

Flexible crystal structures, which exhibit single-crystal-to-single-crystal (SCSC) transformations, are attracting attention in many applied aspects: magnetic switches, catalysis, ferroelectrics and sorption. Acid treatment for titanosilicate material AM-4 and natural compounds with the same structures led to SCSC transformation by loss Na+, Li+ and Zn2+ cations with large structural changes (20% of the unit-cell volume). The conservation of crystallinity through complex transformation is possible due to the formation of a strong hydrogen bonding system. The mechanism of transformation has been characterized using single-crystal X-ray diffraction analysis, powder diffraction, Rietvield refinement, Raman spectroscopy and electron microscopy. The low migration energy of cations in the considered materials is confirmed using bond-valence and density functional theory calculations, and the ion conductivity of the AM-4 family's materials has been experimentally verified. [ABSTRACT FROM AUTHOR]

The chemical and structural diversity of minerals containing sulfur as an essential mineral-forming element has been analyzed in terms of the concept of mineral systems and the information-based structural and chemical complexity parameters. The study employs data for 1118 sulfur mineral species approved by the International Mineralogical Association. All known sulfur minerals belong to nine mineral systems, with the number of essential components ranging from one to nine. The chemical and structural complexity of S minerals correlate with each other; that is, on average, chemical complexification results in structural complexification. The minerals with S–O bonds (sulfates and sulfites) are more complex than those without S–O bonds (sulfides and sulfosalts). However, the most complex sulfur mineral known so far is incomsartorite, Tl6Pb144As246S516, a sulfosalt. The complexity-generating mechanism in sulfides and sulfosalts is the complex combination of different modules excised from parent PbS or SnS archetypes with the subsequent formation of superstructures. The drivers for structural complexity in sulfates are more diverse and, in addition to modular construction and superstructures, also include a high hydration state, the presence of polyatomic clusters, and framework complexity. The most complex Martian minerals are most probably halotrichite-group minerals. The chemical and structural complexity increases with the passage of geological time with the formation of the most complex sulfosalts at Lengenbach (Swiss Alps) triggered by life (activity of sulfur-reducing bacteria). [ABSTRACT FROM AUTHOR]

Single crystals of Na2Cu+[Cu2+3O](AsO4)2Cl (1) and Cu3[Cu3O]2(PO4)4Cl2 (2) were prepared by chemical vapor transport reactions. Both crystal structures are based upon the same [O2Cu6]8+ chains formed by corner-sharing (OCu4)6+ tetrahedra and interconnected by (TO4)3− (T = P, As) tetrahedra into porous {[OCu3](TO4)2Cl}3− frameworks. The channels within the frameworks are occupied by Na+, Cu+ and Cl− ions in the crystal structure of 1, whereas the channels in the structure of 2 contain edge-sharing CuO4Cl tetragonal pyramids. Both compounds are structurally related to the previously described synthetic Na2Cu+[Cu2+3O](PO4)2Cl and NaCu2+[Cu2+3O](PO4)2Cl. The compound 2 is structurally and chemically related to yaroshevskite, Cu3[Cu3O]2(VO4)4Cl2, a mineral discovered in volcanic fumaroles, but the two structure types are drastically different. The crystal chemical analysis of the title and related compounds allows to recognize a family of at least four compounds based upon {[OCu3](TO4)2Cl}3− frameworks with channels occupied by different chemical constituents. [ABSTRACT FROM AUTHOR]

The complexities of chemical composition and crystal structure are fundamental characteristics of minerals that have high relevance to the understanding of their stability, occurrence and evolution. This review summarises recent developments in the field of mineral complexity and outlines possible directions for its future elaboration. The database of structural and chemical complexity parameters of minerals is updated by H-correction of structures with unknown H positions and the inclusion of new data. The revised average complexity values (arithmetic means) for all minerals are 3.54(2) bits/atom and 345(10) bits/cell (based upon 4443 structure reports). The distributions of atomic information amounts, chemIG and strIG, versus the number of mineral species fit the normal modes, whereas the distributions of total complexities, chemIG,total and strIG,total, along with numbers of atoms per formula and per unit cell are log normal. The three most complex mineral species known today are ewingite, morrisonite and ilmajokite, all either discovered or structurally characterised within the last five years. The most important complexity-generating mechanisms in minerals are: (1) the presence of isolated large clusters; (2) the presence of large clusters linked together to form three-dimensional frameworks; (3) formation of complex three-dimensional modular frameworks; (4) formation of complex modular layers; (5) high hydration state in salts with complex heteropolyhedral units; and (6) formation of ordered superstructures of relatively simple structure types. The relations between symmetry and complexity are considered. The analysis of temporal dynamics of mineralogical discoveries since 1875 with the step of 25 years show the increasing chemical and structural complexities of human knowledge of the mineral kingdom in the history of mineralogy. In the Earth's history, both diversity and complexity of minerals experience dramatic increases associated with the formation of Earth's continental crust, initiation of plate tectonics and the Great Oxidation event. [ABSTRACT FROM AUTHOR]

Perryite, natural Ni-silicide, is a minor but regular constituent of the metal phase in enstatite chondrite (aubrite) and enstatite chondrite meteorites. Its synthetic analog was shown to have promising catalytic properties. The first-time solution of the crystal structure of natural perryite was completed on the material from the Mount Egerton aubrite. The mineral is trigonal, R-3c, a = 6.6525(5), c = 37.998(5) Å, V = 1456.3(3) and Z = 6. The structure was refined to R1 = 0.0137 based on 457 independent observed reflections. The chemical formula obtained from the structure refinement, (Ni14.14Fe1.88)S16.02PSi5, agrees with that derived from the electron microprobe data, (Ni13.39Fe2.65Co0.01)S16.05P1.22Si4.74. This research showed that P and Si in perryite are ordered, resulting in the simplified formula (Ni,Fe)16PSi8, in contrast to the currently accepted variant (Ni,Fe)8(Si,P)3. The detailed results of EBSD study reveal previously unknown relationships between perryite, associated a-(Fe,Ni) metal (also known as kamacite) and schreibersite, (Fe,Ni)3P. Since enstatitic meteorites represent the early stages of nebular accretion, our results demonstrate that the crystal-chemical factor could affect the differentiation of chemical elements upon the onset of the Solar System formation. [ABSTRACT FROM AUTHOR]

The crystal structure of nikmelnikovite, Ca12Fe2+Fe3+3Al3(SiO4)6(OH)20, a new member of the garnet supergroup from Kovdor massif, Kola Peninsula, Russia (R $\bar{3}$ , a = 17.2072(6), c = 10.5689(4) Å, V = 2710.1(2) Å3 and Z = 3) has been refined to R1 = 0.046 on the basis of 1184 unique observed reflections. Nikmelnikovite is the first mineral species in the garnet supergroup that has a trigonal (rhombohedral) symmetry. The relationship between its unit cell and the pseudocubic (ideal garnet) unit cell can be described by the transformation matrix [1 $\bar{1}$ 0 | 01 $\bar{1}$ | ½½½]. The crystal-chemical relations between the ideal Ia $\bar{3}$ d garnet and the nikmelnikovite structure type can be described by the following series of imaginary modifications: (1) the symmetry is lowered according to the Ia $\bar{3}$ d → R $\bar{3}$ group–subgroup relationship; (2) the cation sites are split according to the following sequences: X → {X1, X2}; Y → {Y1, Y2, Y3, Y4}; Z → {Z1, Z2}; (3) the X sites remain fully occupied by Ca; (4) each Y site is occupied predominantly by a distinct chemical species: Y1 → Al (Al site), Y2 → Fe2+ (Fe1 site), Y3 → Fe3+ (Fe2 site), Y4 → vacancy (Mn site); (5) one of the Z sites (Z1) is occupied by Si, whereas the other site (Z2) is predominantly vacant. The crystal-chemical formula that takes into account the transition between the archetype and the nikmelnikovite structure type can be described as X{Ca12}Y[Fe2+Al4Fe3+2□]Z(Si6□6)O24(OH)20□4. The structural complexity of nikmelnikovite (4.529 bit/atom and 434.431 bit/cell, after H-correction) is higher than those for andradite, grossular and katoite, which is typical for low-temperature minerals formed after primary minerals with simpler structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • the review of structural diversity of antiperovskites includes more than 280 compounds. • the review covers a wide range of chemical compounds, including oxides, halogenides, nitrides, etc. • 45 topological types of antiperovskite units are considered and analysed. • the topological principles of antiperovskite constructions are formulated. • topological complexity analysis is performed using the information-theory methods. The overview of more than 280 antiperovskites as compounds based upon the units formed by condensation of XA 6 anion-centered octahedra (X = anion; A = cation) shows that there are forty-five topologically different types of antiperovskite structures, including eighteen frameworks, fourteen layers, six chains and seven finite clusters. The XA 6 octahedra may polymerize by sharing common corners, edges and faces. One A atom may be shared by no more than six XA 6 octahedra, whereas one A-A edge may be shared by no more than three octahedra. The average connectivity of an octahedron in the unit, < s >, defined as the average number of octahedra linked to a single octahedron in the complex, correlates positively with the X:A ratio. The information-based analysis of topological complexity of antiperovskite units shows that most antiperovskites are rather simple from the structural point of view with the most complex units being the layers present in the crystal structures of A 4 [N 8 O 3 A 47 ](A'N 4) 12 (A = Ca, Sr; A' = Mo, W). The information-based complexity parameters correlate with the number k' of symmetrically independent octahedra in the antiperovskite unit: the higher the value of k' , the more complex is the unit. From the chemical point of view, the review covers oxides, suboxides, oxysalts, nitrides, subnitrides, and complex halogenides. [ABSTRACT FROM AUTHOR]

The main goal of the paper is to contribute to the agenda of developing an algorithmic model for crystallization and measuring the complexity of crystals by constructing embeddings of 3D parallelohedra into a primitive cubic network (pcu net). It is proved that any parallelohedron P as well as tiling by P, except the rhombic dodecahedron, can be embedded into the 3D pcu net. It is proved that for the rhombic dodecahedron embedding into the 3D pcu net does not exist; however, embedding into the 4D pcu net exists. The question of how many ways the embedding of a parallelohedron can be constructed is answered. For each parallelohedron, the deterministic finite automaton is developed which models the growth of the crystalline structure with the same combinatorial type as the given parallelohedron. [ABSTRACT FROM AUTHOR]

Most research on polyoxometalates (POMs) has been devoted to synthetic compounds. However, recent mineralogical discoveries of POMs in mineral structures demonstrate their importance in geochemical systems. In total, 15 different types of POM nanoscale‐size clusters in minerals are described herein, which occur in 42 different mineral species. The topological diversity of POM clusters in minerals is rather restricted compared to the multitude of moieties reported for synthetic compounds, but the lists of synthetic and natural POMs do not overlap completely. The metal–oxo clusters in the crystal structures of the vanarsite‐group minerals ([As3+V4+2V5+10As5+6O51]7−), bouazzerite and whitecapsite ([M3+3Fe7(AsO4)9O8–;n(OH)n]), putnisite ([Cr3+8(OH)16(CO3)8]8−), and ewingite ([(UO2)24(CO3)30O4(OH)12(H2O)8]32−) contain metal–oxo clusters that have no close chemical or topological analogues in synthetic chemistry. The interesting feature of the POM cluster topologies in minerals is the presence of unusual coordination of metal atoms enforced by the topological restraints imposed upon the cluster geometry (the cubic coordination of Fe3+ and Ti4+ ions in arsmirandite and lehmannite, respectively, and the trigonal prismatic coordination of Fe3+ in bouazzerite and whitecapsite). Complexity analysis indicates that ewingite and morrisonite are the first and the second most structurally complex minerals known so far. The formation of nanoscale clusters can be viewed as one of the leading mechanisms of generating structural complexity in both minerals and synthetic inorganic crystalline compounds. The discovery of POM minerals is one of the specific landmarks of descriptive mineralogy and mineralogical crystallography of our time. [ABSTRACT FROM AUTHOR]

Hydrotalcite, ideally [Mg6Al2(OH)16](CO3)(H2O)4, was studied in samples from Dypingdal, Snarum, Norway (3 R and 2 H), Zelentsovskaya pit (2 H) and Praskovie–Evgenievskaya pit (2 H) (both Southern Urals, Russia), Talnakh, Siberia, Russia (3 R), Khibiny, Kola, Russia (3 R), and St. Lawrence, New York, USA (3 R and 2 H). Two polytypes, 3 R and 2 H (both 'classical'), were confirmed on the basis of single-crystal and powder X-ray diffraction data. Their chemical composition was studied by electron-microprobe analysis, infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The crystal structure of hydrotalcite-3 R was solved by direct methods in the space group R $ {\bar 3} $ m on three crystals (two data collections at 290 K and one at 120 K). The unit-cell parameters are as follows (290/290/120 K): a = 3.0728(9)/3.0626(3)/3.0617(4), c = 23.326(9)/23.313(3)/23.203(3) Å and V = 190.7(1)/189.37(4)/188.36(4) Å3. The crystal structures were refined on the basis of 304/150/101 reflections to R 1 = 0.075/0.041/0.038. Hydrotalcite-2 H crystallises in the P 63/ mmc space group; unit-cell parameters for two crystals are (data collection at 290 K and 93 K): a = 3.046(1)/3.0521(9), c = 15.447(6)/15.439(4) Å, V = 124.39(8)/124.55(8) Å3. The crystal structures were refined on the basis of 160/142 reflections to R 1 = 0.077/0.059. This paper reports the first single-crystal structure data on hydrotalcite. Hydrotalcite distribution in Nature, diagnostic features, polytypism, interlayer topology and localisation of M 2+– M 3+ cations within metal hydroxide layers are discussed. [ABSTRACT FROM AUTHOR]

Philipsburgite, Cu5Zn((As,P)O4)2(OH)6·H2O, from the Middle Pit, Gold Hill Mine, Tooele Co., Utah, USA, was studied by single-crystal X-ray diffraction and scanning electron microscopy. The empirical formula of the studied sample is (Cu4.69Zn1.23)(As0.86P0.18O4)2(OH)5.61·H2O, which agrees well with the previous reports on the mineral. Philipsburgite is monoclinic, P21/c, a = 12.385(6), b = 9.261(4), c = 10.770(5) Å, β = 97.10(1)o, V = 1225.7(9) Å3 (at 100 K), and Z = 4. The crystal structure was refined to R1 = 0.046 for 2563 unique observed reflections with |Fo| ≥ 4σF. The crystal structure of philipsburgite is isotypic to that of kipushite and can be considered as a complex three-dimensional framework consisting of two types of layers stacked parallel to the a-axis. The A-type layer is formed by the edge-sharing Jahn-Teller-distorted Cuφ6 octahedra [φ = O2−, (OH)−, H2O]. Two adjacent octahedral layers are linked via (As2O4) tetrahedra. The B-type layer is built by corner-sharing (ZnO4) and (As1O4) tetrahedra and is formed by the four- and eight-membered tetrahedral rings. The A:B ratio of the A and B layers is equal to 2:1. The hydrogen bonding network in philipsburgite is rather complex and consists of two- and three-center hydrogen bonds. The As1 site accommodates ca. 18% of P and is a preferable position for the P substitution in philipsburgite. The observed selectivity of the As1 site for P may indicate that, for the intermediate compositions with the P:As ratios close to 1:1, there is a fully ordered species with P prevalent at the As1 site and As prevalent at the As2 site. The intermediate composition would, therefore, be Cu5Zn(AsO4)(PO4)(OH)6·H2O and such a mineral can be considered as a separate species, according to the rules of the International Mineralogical Association (IMA). Philipsburgite should be considered as structurally complex with the Shannon information contents of 4.954 bits/atom and 614.320 bits/cell. The obvious reason for the structural complexity of the mineral is its modularity, i.e., the presence of two structurally distinct modules, the octahedral-tetrahedral (A) and tetrahedral (B) layers. [ABSTRACT FROM AUTHOR]

Kurchatovite and clinokurchatovite, both of ideal composition CaMgB2O5, from the type localities (Solongo, Buryatia, Russia, and Sayak-IV, Kazakhstan, respectively) have been studied using electron microprobe and single-crystal X-ray diffraction methods. The empirical formulae of the samples are Ca1.01Mg0.87Mn0.11Fe2+0.02B1.99O5 and Ca0.94Mg0.91Fe2+0.10Mn0.04B2.01O5 for kurchatovite and clinokurchatovite, respectively. The crystal structures of the two minerals are similar and based upon two-dimensional blocks arranged parallel to the c axis in kurchatovite and parallel to the a axis in clinokurchatovite. The blocks are built up from diborate B2O5 groups, and Ca2+ and Mg2+ cations in seven- and six-fold coordination, respectively. Detailed analysis of geometrical parameters of the adjacent blocks reveals that symmetrically different diborate groups have different degrees of conformation in terms of the δ angles between the planes of two BO3 triangles sharing a common O atom, featuring two discrete sets of the δ values of ca. 55° (B' blocks) and 34° (B" blocks). The stacking of the blocks in clinokurchatovite can be presented as ...(+B')(+B")(+B')(+B")... or [(+B')(+B")], whereas in kurchatovite it is more complex and corresponds to the sequence ...(+B')(+B")(+B')(-B')(-B")(-B')(+B')(+B")(+B')(-B')(-B")(-B')... or [(+B')(+B")(+B')(-B')(-B")(-B')]. The B':B" ratios for clinokurchatovite and kurchatovite are 1:1 and 2:1, respectively. According to this description, the two minerals cannot be considered as polytypes and their mutual relationship corresponds to the term modular polymorphs. From the viewpoint of information-based measures of structural complexity, clinokurchatovite (IG = 4.170 bits/atom and IG, total = 300.235 bits/cell) is structurally simpler than kurchatovite (IG = 4.755 bits/atom and IG, total = 1027.056 bits/cell). The high structural complexity of kurchatovite can be inferred from the modular character of its structure. The analysis of structural combinatorics in terms of the modular approach allows to construct the whole family of theoretically possible "kurchatovite"-type structures that bear the same structural features common for kurchatovite and clinokurchatovite. However, the crystal structures of the latter minerals are the simplest and are the only ones that have been observed in nature. The absence of other possible structures is remarkable and can be explained by either the maximum-entropy of the least-action fundamental principles. [ABSTRACT FROM AUTHOR]

The Fedorov–Groth law points out that, on average, chemical simplicity corresponds to higher symmetry, and chemically complex compounds usually have lower symmetry than chemically simple compounds. Using mineralogical data, it is demonstrated that the Fedorov–Groth law is valid and statistically meaningful, when chemical complexity is expressed as the amount of Shannon chemical information per atom and the degree of symmetry as the order of the point group of a mineral. [ABSTRACT FROM AUTHOR]

A novel polymorph of RbCuCl3 (rubidium copper trichloride), denoted ϵ‐RbCuCl3, has been prepared by chemical vapour transport (CVT) from a mixture of CuO, CuCl2, SeO2 and RbCl. The new polymorph crystallizes in the orthorhombic space group C2221. The crystal structure is based on an octahedral framework of the 4H perovskite type. The Rb+ and Cl− ions form a four‐layer closest‐packing array with an ABCB sequence. The Cu2+ cations reside in octahedral cavities with a typical [4 + 2]‐Jahn–Teller‐distorted coordination, forming four short and two long Cu—Cl bonds. ϵ‐RbCuCl3 is the most structurally complex and most dense among all currently known RbCuCl3 polymorphs, which allows us to suggest that it is a high‐pressure phase, which is unstable under ambient conditions. [ABSTRACT FROM AUTHOR]

Two quintinite polytypes, 3 R and 2 T , which are new for the Kovdor alkaline-ultrabasic complex, have been structurally characterized. The crystal structure of quintinite-2 T was solved by direct methods and refined to R 1 = 0.048 on the basis of 330 unique reflections. The structure is trigonal, P $\bar 3$ c 1, a = 5.2720(6), c = 15.113(3) Å and V = 363.76(8) Å3. The crystal structure consists of [Mg2Al(OH)6]+ brucite-type layers with an ordered distribution of Mg2+ and Al3+ cations according to the $\sqrt 3 $ × $\sqrt 3 $ superstructure with the layers stacked according to a hexagonal type. The complete layer stacking sequence can be described as ... =Ab 1 C = Cb1A =.... The crystal structure of quintinite-3 R was solved by direct methods and refined to R 1 = 0.022 on the basis of 140 unique reflections. It is trigonal, R $\bar 3$ m , a = 3.063(1), c = 22.674(9) Å and V = 184.2(1) Å3. The crystal structure is based upon double hydroxide layers [ M 2+,3+(OH)2] with disordered distribution of Mg, Al and Fe and with the layers stacked according to a rhombohedral type. The stacking sequence of layers can be expressed as ... =АB = BC = CA =... The study of morphologically different quintinite generations grown on one another detected the following natural sequence of polytype formation: 2 H → 2 T → 1 M that can be attributed to a decrease of temperature during crystallization. According to the information-based approach to structural complexity, this sequence corresponds to the increasing structural information per atom (I G): 1.522 → 1.706 → 2.440 bits, respectively. As the I G value contributes negatively to the configurational entropy of crystalline solids, the evolution of polytypic modifications during crystallization corresponds to the decreasing configurational entropy. This is in agreement with the general principle that decreasing temperature corresponds to the appearance of more complex structures. [ABSTRACT FROM AUTHOR]

Complexity is one of the important characteristics of crystal structures, which can be measured as the amount of Shannon information per atom or per unit cell. Since complexity may arise due to combination of different factors, herein we suggest a method of ladder diagrams for the analysis of contributions to structural complexity from different crystal-chemical phenomena (topological complexity, superstructures, modularity, hydration state, etc.). The group of minerals and inorganic compounds based upon the batagayite-type [M(TO4)Ï•] layers (M = Fe, Mg, Mn, Ni, Zn, Co; T = P, As; Ï• = OH, H2O) is used as an example. It is demonstrated that the method allows for the quantitative estimates of various contributions to the complexity of the whole structure. [ABSTRACT FROM AUTHOR]

Three novel copper compounds, Rb4Cu4OCl10 (I), Rb[Cu3O](SeO3)2Cl (II), and RbCu3(OH)(SeO3)Cl4(H2O)3 (III) were prepared by chemical vapor transport (CVT) reactions method from mixtures of CuO, SeO2, RbCl, and CuCl2. The crystal structures of the three compounds were determined by direct methods. Compound I is a Rb analogue of ponomarevite, K4Cu4OCl10. Its crystal structure contains {[OCu4]Cl10}4- clusters with oxocentered [OCu4]6+ tetrahedra as cores. The clusters are linked by the Rb+ cations. The crystal structure of II contains complex {[O2Cu6](SeO3)4Cl2}2- layers formed by dimers of edge-sharing [OCu4]6+ tetrahedra interlinked via selenite groups and Cl- anions. The crystal structure of III is based upon {[(OH)Cu3](SeO3)}3+ layers formed by the [(OH)Cu3]5+ tetrahedra attached to (SeO3)2- groups. The layers are linked via Cl- anions and via hydrogen bonds to H2O molecules. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) is used to determine positions of H atoms and to investigate hydrogen bonding in the crystal structures of two polymorphs of Cu3(AsO4)(OH)3: clinoclase and gilmarite. Hydrogen bonds in clinoclase involve interactions between hydroxyl groups and O atoms of arsenate tetrahedra, whereas the crystal structure of gilmarite features OH···OH bonding, which is rather uncommon in copper hydroxy-oxysalts. Information-based parameters of structural complexity for clinoclase and gilmarite show that the former is more complex (IG,total = 213.212 bits/cell) than the latter (IG,total = 53.303 bits/cell), which indirectly points out that gilmarite is metastable. This suggestion is supported by the lower density of gilmarite (4.264 g/cm3) compared to that of clinoclase (4.397 g/cm3). The hypothesis of metastable character of gilmarite is in agreement with the Goldsmith's simplexity principle and the Ostwald-Volmer rule. [ABSTRACT FROM AUTHOR]

Single crystals of four novel uranyl selenate and selenite-selenate oxysalts with protonated ethylamine molecules, (C 2 H 8 N) 2 [(UO 2 )(SeO 4 ) 2 (H 2 O)](H 2 O) ( I ), (C 2 H 8 N) 3 [(UO 2 )(SeO 4 ) 2 (HSeO 4 )] ( II ), (C 2 H 8 N)[(UO 2 )(SeO 4 )(HSeO 3 )] ( III ), and (C 2 H 8 N)(H 3 O)[(UO 2 )(SeO 4 ) 2 (H 2 O)] ( IV ) have been prepared by isothermal evaporation from aqueous solutions. Uranyl-containing 1D and 2D units have been investigated using topological approach and information-based complexity measurements that demonstrate the evolution of structural units and the increase of topological complexity with the decrease of H 2 O content. [ABSTRACT FROM AUTHOR]

The review is devoted to the start-of-the-art of the description, interpretation and classification of crystal structures in mineralogy. Among methods, the focus is on the atomic packings (including both anion and cation arrays), coordination polyhedra (both cation- and anion-centred), the concept of fundamental building blocks and related ideas, the use of networks, graphs and tilings (space partitions). The basic concepts under discussion in modern structural mineralogy include structure hierarchy (specification and compositional hierarchies are considered separately), modularity (representation of crystal structures as constructed from modules extracted from simple archetype structures) and complexity (with emphasis on static or informational and algorithmic complexities). Short historical notes are given for all of the topics considered. [ABSTRACT FROM PUBLISHER]

The tendency of high-valence xenon to form consolidated oxide structures is herein supported by the study of K4Xe3O12, the first example of a layered xenon perovskite. Xenon seems to be the only nontransition element that can adopt single-cation oxide perovskite frameworks. At the same time, peculiarities of electronic structure of xenon impose specific features on the bonding within a perovskite structure. Weak supramolecular interactions known as aerogen bonds are the linkers that maintain structural integrity of perovskite slabs in K4Xe3O12. The occurrence of aerogen bonding can provide an insight into the explosive properties of K4Xe3O12: the weakness of supramolecular interactions allows consideration of them as possible trigger bonds responsible for the detonation sensitivity of layered xenon perovskite. [ABSTRACT FROM AUTHOR]

The article discusses mineralogical crystallography and some special issues related to it, including the topic of crystallography and mineralogy, have been studied for centuries under a single discipline.

Peter Burns was extremely generous in allowing me to pursue my own research directions, simultaneously introducing me to the magic world of uranium mineralogy and crystal chemistry. First, I checked the list of the MSA awardees and medalists over the whole history of the Mineralogical Society of America and found out that I am only the second Russian citizen who was ever honored by any MSA medal. I am deeply honored and very grateful to the Mineralogical Society of America for this high recognition for three reasons. [Extracted from the article]

A new uranyl sulfate, [Co(H2O) 6]3[(UO2)5 (SO4)8 (H2O)](H2O) 5, has been synthesized using mild hydrothermal methods. The structure (monoclinic, P21 /c, a = 27.1597(14), b = 9.9858 (5), c = 22.7803 (12) Å, β = 106.520(1)°, V= 5923.2(5) ų Z = 4) has been solved by direct methods and refined on the basis of F² for all unique reflections to R1 = 0.056, calculated for the 9124 unique observed reflections (|Fo| ≥ 4σ F). It contains five symmetrically distinct uranyl pentagonal bipyra-mids and eight sulfate tetrahedra that link via the sharing of vertices between uranyl polyhedra and sulfate tetrahedra, resulting in sheets parallel to (001). Adjacent sheets are linked by hydrogen bonds to Co2+ (H2O) 6 octahedra and H2O groups located in the interlayer. The uranyl sulfate sheet contains four- and five-connected uranyl pentagonal bipyramids and three- and four-connected sulfate tetrahedra. The sheet may be constructed using modules from related structures involving pentagonal bipyramids and tetrahedra, and is readily described using a nodal representation. In general, the uranyl sulfate sheets in [Co(H2O) 6]3 [(UO2)5(SO4)8 (H2O)](H2O) 5 are more rigid than the structural units typically found in comparable uranyl molybdates, which involve the sharing of vertices between uranyl pentagonal bipyramids and molybdate tetrahedra. [ABSTRACT FROM AUTHOR]

Orange platy crystals of K2Na8 (UO2)8Mo4O24 [(S,Mo)O4, the first known uranium molybdosulfate, have been prepa-red by high-temperature solid-state reactions. The stmcture (monoclinic, C2/c, a = 24.282(4), b = 12.1170(18), c = 13.6174(17) Å, β = 106.33(1)º, V= 3845.0(9) ų Z= 4) has been solved by direct methods and refined to R1 = 0.058 on the basis of 2837 unique observed reflections. The structure consists of a three-dimensional heteropolyhedral framework based upon the [(UO2)4O4(Mo2O10)] layers parallel to (010). The layers are formed by linkage of chains of edge-sharing UO7 bipyramids running along the c axis via the Mo2O10 dimers of edge-sharing MoO6 octahedra. Linkage of the layers into a three-dimensional framework is provided by the MoO4 and SO4 tetrahedra that share comers with the MoO6 octahedra. The Na+ and K+ cations reside in framework cavities in between the uranyl molybdate layers. The stmcture of K2Na8 (UO2)8Mo4O24 [(S,Mo)O4] is yet another complex derivative of the U2MoO8 structure type. [ABSTRACT FROM AUTHOR]

A new mineral beshtauite, (NH4)2(UO2)(SO4)2⋅2H2O, was found in the oxidation zone of the Beshtau uranium deposit, Mount Beshtau, Stavropol region, Northern Caucasus, Russia, and named after the locality. It is associated with rozenite, gypsum, lermontovite, and older marcasite, pyrite, halloysite, and opal. Beshtauite occurs as well-shaped short-prismatic crystals up to 0.1 x 0.15 x 0.2 mm, their clusters and crusts up to 0.5 mm across growing on marcasite. Beshtauite is transparent, light green. The luster is vitreous. The mineral fluoresces strongly yellow-green under both short- and long-wave UV irradiation. It is brittle. The Mohs hardness is ca. 2. Cleavage was not observed. Dcalc is 3.046 g/cm³. Beshtauite is optically biaxial (+), α = 1.566(3), β = 1.566(3), γ = 1.592(3), 2Vmeas < 10°. The chemical composition (wt%, electron microprobe data, H2O by difference) is: (NH4)2O 10.33, UO3 53.21, SO3 29.40, H2Ocalc 7.06, total 100.00. Content of (NH4)2O was calculated from measured nitrogen content: 5.56 wt% N. The empirical formula, calculated on the basis of 12 O apfu, is (NH4)2.12U0.99S1.96O9.91 (H2O) 2.09. Beshtauite is monoclinic, P21/c, a = 7.7360(8), b = 7.3712(5), c = 20.856(2) Å, β = 102.123(8)°, V = 1162.76(19) Å3, Z = 4 (from single-crystal X-ray diffraction data). The strongest reflections of the X-ray powder pattern [d (Å), I(hkl)] are: 6.86, 100(011, 102); 5.997, 19(012); 5.558, 15(102); 5.307, 36(111,110); 5.005, 35(013,112); 3.410, 38(114,204,106); 3.081, 24(016); 2.881, 20(106,123). The crystal structure was solved by direct methods and refined on the basis of 2677 independent reflections with I > 4σ(I) to R1 = 0.093. The structure is based upon [UO2(SO4)2(H2O)]2- layers consisting of corner-sharing UO6 (H2O) pentagonal bipyramids and SO4 tetrahedra. The layers are coplanar to (102) and are linked via hydrogen bonding that involve interlayer NH4+ ions and H2O molecules. Beshtauite is important indicator mineral: its presence can be considered as an evidence of transportation of U6+ in nature in forms of mobile complexes of uranyl cation with ammonia or polyamines. [ABSTRACT FROM AUTHOR]

Compounds with the fresnoite structure type possess remarkable chemical diversity and a range of unique physical properties, including nonlinear optical (NLO) activity. K2Sb(P2O7)F, which was reported recently, belongs to this group and its structure is not novel in terms of either the topology or local coordination geometry around the Sb3+ cations. The crystallographic disorder observed in the fresnoite‐type structures can be explained by twinning, which is frequent for non‐centrosymmetric crystals. It is argued by Krivovichev and Bindi that the previously reported K2Sb(P2O7)F has a fresnoite structure type that is not novel in terms of either the topology or local coordination geometry around the Sb3+ ions. They argue that the crystallographic disorder observed in fresnoite‐type structures can be explained by twinning, which is frequent for non‐centrosymmetric crystals. [ABSTRACT FROM AUTHOR]

Compounds with the fresnoite structure type possess remarkable chemical diversity and a range of unique physical properties, including nonlinear optical (NLO) activity. K2Sb(P2O7)F, which was reported recently, belongs to this group and its structure is not novel in terms of either the topology or local coordination geometry around the Sb3+ cations. The crystallographic disorder observed in the fresnoite‐type structures can be explained by twinning, which is frequent for non‐centrosymmetric crystals. [ABSTRACT FROM AUTHOR]

Nefedovite, Na5Ca4(PO4)4F, has been investigated by in situ high-temperature powder (30–690 °C) and single crystal (27–827 °C) X-ray diffraction and Raman spectroscopy. Nefedovite is tetragonal, space group I-4, a = 11.6560(2), c = 5.4062(2) Å, V = 734.50(2) Å3 (R1 = 0.0149). Nefedovite is a 1D antiperovskite, since its crystal structure contains chains of corner-sharing anion-centered [FCa4Na2]9+ octahedra. The chains are parallel to the c direction. Nefedovite is stable up to 727 °C and undergoes a displacive phase transition in the temperature range 277–327 °C. With increasing temperature, the PO4 tetrahedra in the crystal structure of nefedovite gradually rotate around the imaginary fourfold inversion axes aligning the O2…O3 edge parallel to [110], which ultimately leads to the appearance of the mirror plane perpendicular to the c direction and the change of space group from I-4 (82) to I4/m (87). The crystal structure of nefedovite expands strongly anisotropically with the direction of the maximum thermal expansion oriented perpendicular to the chains of anion-centered octahedra. The information-based structural complexity analysis demonstrates that both low- and high-temperature modifications of nefedovite are structurally simple with the IG,total value less than 100 bits per unit cell. The structural complexity decreases along the phase transition, which is typical for displacive phase transitions. [ABSTRACT FROM AUTHOR]

Synchrotron high-resolution powder X-ray diffraction (HRPXRD) and Rietveld structure refinements were used to examine the crystal structure of single phases and intergrowths (either two or three phases) in 13 samples of the helvine-group minerals, (Zn,Fe,Mn)8[Be6Si6O24]S2. The helvine structure was refined in the cubic space group P 4 ¯ 3 n . For the intergrowths, simultaneous refinements were carried out for each phase. The structural parameters for each phase in an intergrowth are only slightly different from each other. Each phase in an intergrowth has well-defined unit-cell and structural parameters that are significantly different from the three endmembers and these do not represent exsolution or immiscibility gaps in the ternary solid-solution series. The reason for the intergrowths in the helvine-group minerals is not clear considering the similar radii, identical charge, and diffusion among the interstitial M cations (Zn2+, Fe2+, and Mn2+) that are characteristic of elongated tetrahedral coordination. The difference between the radii of Zn2+ and Mn2+ cations is 10%. Depending on the availability of the M cations, intergrowths may occur as the temperature, pressure, fugacity fS2, and fluid composition change on crystallization. The Be–Si atoms are fully ordered. The Be–O and Si–O distances are nearly constant. Several structural parameters (Be–O–Si bridging angle, M–O, M–S, average [4] distances, and TO4 rotational angles) vary linearly with the a unit-cell parameter across the series because of the size of the M cation. [ABSTRACT FROM AUTHOR]

Zolotarevite (IMA2020-076), ideally Na5Zr[Si6O15(ОН)3]⋅2–3H2O, is а new mineral of the lovozerite group. The mineral was found in a leucocratic nepheline syenite from Kedykverpakhk Mt., Lovozero alkaline massif, Kola Peninsula, Russia. It occurs as anhedral grains up to 1 mm across and is associated with microcline–perthite, nepheline, sodalite, aegirine, lamprophyllite, lueshite, umbozerite, lomonosovite, nastrophite, a mineral of the kazakovite–tisinalite series, sphalerite and löllingite. Zolotarevite is cherry red, with a vitreous lustre and white streak. The mineral is brittle, with a Mohs hardness of 5. Cleavage was not observed; the fracture is uneven. The measured density is 2.75(5) g⋅cm–3, the density calculated using the empirical formula and single-crystal unit-cell parameters is 2.85 g⋅cm–3. Zolotarevite is anomalously biaxial (–), α = 1.580(2), β = 1.600(2) and γ = 1.602(2) (for λ = 589 nm); 2Vmeas < 10°. Chemical data (electron microprobe, wt.%) are: Na2O 20.41, СаО 0.42, MnO 3.49, Fе2O3 0.55, SiO2 52.46, ТiO2 1.34, ZrO2 11.33, H2O (calculated from the structural formula) 10.20, total 100.20. The empirical formula based оn 6 Si atoms per formula unit is Na4.53Zr0.63Mn0.34Ti0.11Ca0.05Fe3+0.05Si6O14.43(ОН)3.56(H2О)2.11. Zolotarevite is trigonal, space group R ${\bar 3}$ m, with a = 10.294(6) Å, c = 13.115(8) Å, V = 1203.7(16) Å3 and Z = 3. The crystal structure was solved from single-crystal data and refined to R1 = 0.049. The strongest lines of the powder X-ray diffraction pattern [d in Å (I) (hkl)] are: 7.37 (69) (101); 5.26 (56) (012); 3.686 (64) (202); 3.330 (79) (113); 3.265 (99) (211), 2.640 (100) (024) and 2.576 (60) (220). Zolotarevite is unique in that it is a highly hydrated lovozerite-group mineral with the B site occupied by variable amounts of H2O. [ABSTRACT FROM AUTHOR]

The chemical diversity and complexity of tellurium minerals were analyzed using the concept of mineral systems and Shannon informational entropy. The study employed data for 176 Te mineral species known today. Tellurium minerals belong to six mineral systems in the range of one-to-six species-defining elements. For 176 tellurium minerals, only 36 chemical elements act as essential species-defining constituents. The numbers of minerals of main elements are calculated as follows (the number of mineral species is given in parentheses): O (89), H (48), Cu (48), Pb (43), Bi (31), S (29), Ag (20), Fe (20), Pd (16), Cl (13), and Zn (11). In accordance with their chemistry, all Te minerals are classified into five types of mineral systems: tellurium, oxides, tellurides and intermetalides, tellurites, and tellurates. A statistical analysis showed positive relationships between the chemical, structural, and crystallochemical complexities and the number of essential species-defining elements in a mineral. A positive statistically significant relationship between chemical and structural complexities was established. It is shown that oxygen-free and oxygen-bearing Te minerals differ sharply from each other in terms of chemical and structural complexity, with the first group of minerals being simpler than the second group. The oxygen-free Te minerals (tellurium, tellurides, and intermetallides) are formed under reducing conditions with the participation of hydrothermal solutions. The most structurally complex oxygen-bearing Te minerals originate either from chemical weathering and the oxidation of ore deposits or from volcanic exhalations (Nabokoite). [ABSTRACT FROM AUTHOR]

Xenophyllite, ideally Na4Fe7(PO4)6, is a rare meteoritic phosphate found in phosphide-phosphate assemblages confined to troilite nodules of the Augustinovka iron meteorite (medium octahedrite, IIIAB). The mineral occurs as tiny lamella up to 0.15 mm long cross-cutting millimeter-sized grains of sarcopside, Fe3(PO4)2, associated with schreibersite, chromite and pentlandite. Xenophyllite is translucent, has a bluish-green to grey-green color and vitreous lustre. Moh's hardness is 3.5–4. Cleavage is perfect on {001}. Measured density is 3.58(5) g/cm3. The mineral is biaxial (−), 2V 10–20°, with refractive indexes: α 1.675(2), β 1.681(2), γ 1.681 (2). Chemical composition of the holotype specimen (electron microprobe, wt.%) is: Na2O 10.9, K2O 0.4, MnO 5.8, FeO 42.1, Cr2O3 0.8, P2O5 40.7, total 100.7, corresponding to the empirical formula (Na3.67K0.09)Σ3.76(Fe2+6.12Mn2+0.85Cr0.11)Σ7.08P5.99O24.00. Xenophyllite is triclinic, P1 or P-1, a 9.643(6), b 9.633(5), c 17.645(11) Å; α 88.26(5), β 88.16(5), γ 64.83(5)°, V 1482(2) Å3, Z = 3. The toichiome C-centered subcell has the following dimensions: a 16.257(9), b 10.318(8), c 6.257(9) Å, β = 112.77(9)°, V 968(2) Å3, Z = 2. Xenophyllite is structurally related to synthetic phosphate Kna3Fe7(PO4)6 having a channel-type structure, and galileiite, NaFe4(PO4)3. The variations of chemical composition of xenophyllite ranging from Na4Fe7(PO4)6 to almost Na2Fe8(PO4)6 are accounted for by Na-ions mobility. The latter property makes xenophyllite a promising prototype for cathode materials used in sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Single crystals of the novel boroarsenate (K,Na)2[As2B12O24][B3O3(OH)3] (I) were obtained using the borax flux method. The crystal structure of I was found to be triclinic, P-1, a = 8.414(5), b = 10.173(6), c = 15.90(1) Å, α = 79.56(1), β = 78.68(1), γ = 70.91(1), V = 1251(1) Å3, Z = 2. The crystal structure of I is based upon the novel [AsB6O12]− microporous boroarsenate framework formed by B and As coordination polyhedra. This framework can be subdivided into borate units that are interlinked by AsO4 tetrahedra. In the case of I, the borate substructure is a chain consisting of triborate rings, ☐2Δ, formed by two (BO3) triangles and one (BO4) tetrahedron connected through shared common oxygen atoms. The chains are extended along [0 1 ¯ 1] and are interlinked by (AsO4) tetrahedra in the [011] direction. As a result, the framework has large channels parallel to [100], having an effective diameter of 4.2 × 5.6 Å2. The channels contain occluded electroneutral ring triborate complexes, [B3O3(OH)3]0, formed by three (BO2(OH−))− triangles sharing common O atoms, as well as K+ and Na+ cations. The triborate [B3O3(OH)3]0 units correspond to similar clusters found in the crystal structure of the α-form of metaboric acid, HBO2. According to information-based complexity calculations, the crystal structure of I should be described as complex, with IG = 5.781 bits/atom and IG,total = 625.950 bits/cell. Teruggite, Ca4Mg[B6As(OH)6O11]2(H2O)14, the only known boroarsenate of natural origin, has almost twice as much information per unit cell, with IG,total = 1201.992 bits/cell. The observed difference in structural complexity between I and teruggite is the consequence of their chemistry (hydration state) and different formation conditions. [ABSTRACT FROM AUTHOR]

The crystal structure of dmisteinbergite has been determined using crystals from the type locality in Kopeisk city, Chelyabinsk area, Southern Urals, Russia. The mineral is trigonal, with the following structure: P312, a = 5.1123(2), c = 14.7420(7) Å, V = 333.67(3) Å3, R1 = 0.045, for 762 unique observed reflections. The most intense bands of the Raman spectra at 327s, 439s, 892s, and 912s cm −1 correspond to different types of tetrahedral stretching vibrations: Si–O, Al–O, O–Si–O, and O–Al–O. The weak bands at 487w, 503w, and 801w cm−1 can be attributed to the valence and deformation modes of Si–O and Al–O bond vibrations in tetrahedra. The weak bands in the range of 70–200 cm−1 can be attributed to Ca–O bond vibrations or lattice modes. The crystal structure of dmisteinbergite is based upon double layers of six-membered rings of corner-sharing AlO4 and SiO4 tetrahedra. The obtained model shows an ordering of Al and Si over four distinct crystallographic sites with tetrahedral coordination, which is evident from the average bond lengths (T = Al, Si), equal to 1.666, 1.713, 1.611, and 1.748 Å for T1, T2, T3, and T4, respectively. One of the oxygen sites (O4) is split, suggesting the existence of two possible conformations of the [Al2Si2O8]2− layers, with different systems of ditrigonal distortions in the adjacent single layers. The observed disorder has a direct influence upon the geometry of the interlayer space and the coordination of the Ca2 site. Whereas the coordination of the Ca1 site is not influenced by the disorder and is trigonal antiprismatic (distorted octahedral), the coordination environment of the Ca2 site includes disordered O atoms and is either trigonal prismatic or trigonal antiprismatic. The observed structural features suggest the possible existence of different varieties of dmisteinbergite that may differ in: (i) degree of disorder of the Al/Si tetrahedral sites, with completely disordered structure having the P63/mcm symmetry; (ii) degree of disorder of the O sites, which may have a direct influence on the coordination features of the Ca2+ cations; (iii) polytypic variations (different stacking sequences and layer shifts). The formation of dmisteinbergite is usually associated with metastable crystallization in both natural and synthetic systems, indicating the kinetic nature of this phase. Information-based complexity calculations indicate that the crystal structures of metastable CaAl2Si2O8 polymorphs dmisteinbergite and svyatoslavite are structurally and topologically simpler than that of their stable counterpart, anorthite, which is in good agreement with Goldsmith's simplexity principle and similar previous observations. [ABSTRACT FROM AUTHOR]

Ivanyuk family gathering on 2016 New Year's Eve: Mikhail (front centre), Gregory, Ayya with grandson Ostap, Viya and Taras (from left to right), Polina with Aglaya (back). Two papers by Dey I et al. i (2021a, b) report the paragenesis and compositional variation of different pyrochlore populations in albitites, dolomite and silicate-rich carbonatites from the Sevattur carbonatite complex, India. Oscillatory- and sector-zoned pyrochlore from carbonatites of the Kerimasi volcano, Gregory rift, Tanzania. Mineralogy and petrology of alkaline rocks and carbonatites: Celebrating the life and work of Gregory Yu. [Extracted from the article]

Anthropogenic rapidcreekite, Ca2(SO4)(CO3)·4H2O, from burnt dumps of coal mines in the Chelyabinsk coal basin, South Urals, Russia, previously described as 'korkinoite', has been studied by single-crystal X-ray diffraction, high-temperature powder X-ray diffraction, infrared (IR) and Raman spectroscopy. The mineral is orthorhombic, Pcnb, a = 15.5334(6) Å, b = 19.2379(7) Å, c = 6.1625(3) Å, V = 1841.54(13) Å3. The crystal structure is based upon heteropolyhedral sheets parallel to (100) and can be described as produced from the crystal structure of gypsum by chemical twinning. The Ca1 and Ca2 sites are coordinated by six O atoms and two H2O molecules each. The CaO8 polyhedra form chains parallel to the с axis, connected via CO3 groups and SO4 tetrahedra to form a two-dimensional arrangement. The sheets are linked to each other by means of the hydrogen bonding network. The main bands of the IR and Raman spectra correspond to symmetric and asymmetric vibrations in the SO42- tetrahedra and CO32- groups. The OH-stretching region possesses high-intensity peaks. 'Korkinoite' is stable up to 200 °C. Thermal expansion has a strong anisotropic character in the ab and bc planes and is almost isotropic within the ac plane. The thermal expansion coefficients are approximately the same at room temperature and 200 °C (×10-6 °C-1): (αa = 53.7, αb = 11.6, αc = 52.0, αv = 117.3 (25 °C); αa = 53.2, αb = 11.6, αc = 51.6, αv = 116.4 (200 °C)). The maximal thermal expansion is along [100] (perpendicular to the plane of the layers). Both 'korkinoite' (anthropogenic rapidcreekite) and rapidcreekite are structurally related to gypsum due to the unit-cell twinning induced by replacing one-half of sulfate groups in gypsum by carbonate ions in rapidcreekite. These structural relations determine the similarity of thermal behavior of gypsum and rapidcreekite with strongly anisotropic expansion within the sheet of Ca polyhedra and sulfate or sulfate and carbonate groups. The current study confirms that 'korkinoite' is identical to rapidcreekite, except for the insignificant differences in the chemical composition. [ABSTRACT FROM AUTHOR]

Nine different samples of fluorellestadite from Chelyabinsk, Kizel and Kuznetsk coal basins were studied by single-crystal X-ray diffraction analysis, thermal X-ray diffraction (25–800 °C), Infrared (IR) and Raman spectroscopy. Fluorellestadite is hexagonal, space group P63/m, the unit-cell parameters for the nine samples studied vary within rather small ranges: a = 9.415(5) – 9.4808(7) Å, c = 6.906(2) – 6.938(8) Å, V = 530.3(4) – 538.41(9) Å3. The mineral is isotypic with apatite, the structure is based upon isolated TO4 tetrahedra, where the T position is statistically occupied by Si4+ and S6+ with the ideal ratio Si:S equal to 1:1. The fluorine atoms are located in channels of the Ca4[(S,Si)O4]6 framework oriented parallel to the c axis. The thermal expansion of fluorellestadite is almost isotropic in the temperature range 25–800 °C (for ambient temperature: αa = 12.0·10−6 °C−1, αc = 11.9·10−6 °C−1; for 800 °C: αa = 18.2·10−6 °C−1, αc = 18.6·10−6 °C−1). A similar thermal behavior had been observed for fluorapatite. Despite the same structure motifs and close conditions of formation, the samples of fluorellestadite show different S/Si/P occupancies for T site and the F/Cl/OH (X-position) ratios. [ABSTRACT FROM AUTHOR]

Chemical diversity of minerals containing selenium as an essential element has been analyzed in terms of the concept of mineral systems and the information-based structural and chemical complexity parameters. The study employs data for 123 Se mineral species approved by the International Mineralogical Association as of 25 May 2019. All known selenium minerals belong to seven mineral systems with the number of essential components ranging from one to seven. According to their chemical features, the minerals are subdivided into five groups: Native selenium, oxides, selenides, selenites, and selenates. Statistical analysis shows that there are strong and positive correlations between the chemical and structural complexities (measured as amounts of Shannon information per atom and per formula or unit cell) and the number of different chemical elements in a mineral. Analysis of relations between chemical and structural complexities provides strong evidence that there is an overall trend of increasing structural complexity with the increasing chemical complexity. The average structural complexity for Se minerals is equal to 2.4(1) bits per atom and 101(17) bits per unit cell. The chemical and structural complexities of O-free and O-bearing Se minerals are drastically different with the first group being simpler and the second group more complex. The O-free Se minerals (selenides and native Se) are primary minerals; their formation requires reducing conditions and is due to hydrothermal activity. The O-bearing Se minerals (oxides and oxysalts) form in near-surface environment, including oxidation zones of mineral deposits, evaporites and volcanic fumaroles. From the structural viewpoint, the five most complex Se minerals are marthozite, Cu(UO2)3(SeO3)2O2·8H2O (744.5 bits/cell); mandarinoite, Fe2(SeO3)3·6H2O (640.000 bits/cell); carlosruizite, K6Na4Na6Mg10(SeO4)12(IO3)12·12H2O (629.273 bits/cell); prewittite, KPb1.5ZnCu6O2(SeO3)2Cl10 (498.1 bits/cell); and nicksobolevite, Cu7(SeO3)2O2Cl6 (420.168 bits/cell). The mechanisms responsible for the high structural complexity of these minerals are high hydration states (marthozite and mandarinoite), high topological complexity (marthozite, mandarinoite, carlosruizite, nicksobolevite), high chemical complexity (prewittite and carlosruizite), and the presence of relatively large clusters of atoms (carlosruizite and nicksobolevite). In most cases, selenium itself does not play the crucial role in determining structural complexity (there are structural analogues or close species of marthozite, mandarinoite, and carlosruizite that do not contain Se), except for selenite chlorides, where stability of crystal structures is adjusted by the existence of attractive Se–Cl closed-shell interactions impossible for sulfates or phosphates. Most structurally complex Se minerals originate either from relatively low-temperature hydrothermal environments (as marthozite, mandarinoite, and carlosruizite) or from mild (500–700 °C) anhydrous gaseous environments of volcanic fumaroles (prewittite, nicksobolevite). [ABSTRACT FROM AUTHOR]

The crystal structure of paratooite-(La) has been solved using crystals from the type locality, Paratoo copper mine, near Yunta, Olary Province, South Australia, Australia. The mineral is orthorhombic, Pbam, a = 7.2250(3) Å, b = 12.7626(5) Å, c = 10.0559(4) Å, V = 927.25(6) Å3, and R1 = 0.063 for 1299 unique observed reflections. The crystal structure contains eight symmetrically independent cation sites. The La site, which accommodates rare earth elements (REEs), but also contains Sr and Ca, has a tenfold coordination by seven carbonate groups. The Ca, Na1, and Na2 sites are coordinated by eight, eight, and six O atoms, respectively, forming distorted CaO8 and Na1O8 cubes, and Na2O6 octahedra. The Cu site is occupied solely by copper and possess a distorted octahedral coordination with four short (1.941 Å) and two longer (2.676 Å) apical Cu–O bonds. There are three symmetrically independent carbonate groups (CO3)2− with the average bond lengths equal to 1.279, 1.280, and 1.279 Å for the C1, C2, and C3 sites, respectively. The crystal structure of paratooite-(La) can be described as a strongly distorted body-centered lattice formed by metal cations with (CO3)2− groups filling its interstices. According to the chemical and crystal-structure data, the crystal-chemical formula of paratooite-(La) can be described as (La0.74Ca0.11Sr0.07)4CuCa(Na0.75Ca0.15)(Na0.63)(CO3)8 or REE2.96Ca1.59Na1.38CuSr0.28(CO3)8. The idealized formula can be written as (La,Sr,Ca)4CuCa(Na,Ca)2(CO3)8. The structure of paratooite is a 1 × 2 × 2 superstructure of carbocernaite, CaSr(CO3)2. The superstructure arises due to the ordering of the chemically different Cu2+ cations, on one hand, and Na+ and Ca2+ cations, on the other hand. The formation of a superstructure due to the cation ordering in paratooite-(La) compared to carbocernaite results in the multiple increase of structural complexity per unit cell. Therefore, paratooite-(La) versus carbocernaite represents a good example of structural complexity increasing due to the increasing chemical complexity controlled by different electronic properties of mineral-forming chemical elements (transitional versus alkali and alkaline earth metals). [ABSTRACT FROM AUTHOR]

Chlormagaluminite is the only Cl-dominated hydrotalcite-supergroup mineral species with M2+:M3+ = 2:1. The holotype sample of chlormagaluminite from the Kapaevskaya volcanic pipe (Irkutsk Oblast, Siberia, Russia) has been chemically and structurally characterized. The average chemical composition of the mineral is (electron microprobe, OH content is calculated by stoichiometry and H2O from the crystal-structure data, wt. %): MgO 33.85, FeO 1.09, Al2O3 22.07, Cl 14.72, H2Otot 30.96, Cl=O −3.39, total 99.30. The empirical formula based on Mg + Al + Fe = 6 atoms per formula unit (apfu) is [Mg3.91Fe2+0.07Al2.02(OH)12]Cl2.02(H2O)2.0(2). The crystal structure has been solved from single-crystal X-ray diffraction data in the space group P63/mcm, a = 5.268(3), c = 15.297(8) Å and V = 367.6(4) Å3. The refinement converged to R1 = 0.083 on the basis of 152 unique reflections with I > 2σ(I) collected at room conditions. The powder pattern contains standard reflections of a 2H polytype and two additional reflections [(010), d010 = 4.574 Å; (110), d110 = 2.647 Å] indicative of Mg and Al ordering according to the 3 × 3 superstructure. The structure is based upon brucite-type octahedral layers with an ordered distribution of Mg and Al over octahedral sites. The Cl− anions and H2O molecules reside in the interlayer, providing a three-dimensional integrity of the structure. [ABSTRACT FROM AUTHOR]

The crystal structure of a novel natural uranyl sulfate, Ca(UO2)6(SO4)2O2(OH)6·12H2O (CaUS), has been determined using data collected under ambient conditions at the Swiss–Norwegian beamline BM01 of the European Synchrotron Research Facility (ESRF). The compound is monoclinic, P21/c, a = 11.931(2), b = 14.246(6), c = 20.873(4) Å, β = 102.768(15), V = 3460.1(18) Å3, and R1 = 0.172 for 3805 unique observed reflections. The crystal structure contains six symmetrically independent U6+ atoms forming (UO7) pentagonal bipyramids that share O...O edges to form hexamers oriented parallel to the (010) plane and extended along [1–20]. The hexamers are linked via (SO4) groups to form [(UO2)6(SO4)2O2(OH)6(H2O)4]2− chains running along the c-axis. The adjacent chains are arranged into sheets parallel to (010). The Ca2+ ions are coordinated by seven O atoms, and are located in between the sheets, providing their linkage into a three-dimensional structure. The crystal structure of CaUS is closely related to that of uranopilite, (UO2)6(SO4)O2(OH)6·14H2O, which is also based upon uranyl sulfate chains consisting of hexameric units formed by the polymerization of six (UO7) pentagonal bipyramids. However, in uranopilite, each (SO4) tetrahedron shares its four O atoms with (UO7) bipyramids, whereas in CaUS, each sulfate group is linked to three uranyl ions only, and has one O atom (O16) linked to the Ca2+ cation. The chains are also different in the U:S ratio, which is equal to 6:1 for uranopilite and 3:1 for CaUS. The information-based structural complexity parameters for CaUS were calculated taking into account H atoms show that the crystal structure of this phase should be described as very complex, possessing 6.304 bits/atom and 1991.995 bits/cell. The high structural complexity of CaUS can be explained by the high topological complexity of the uranyl sulfate chain based upon uranyl hydroxo/oxo hexamers and the high hydration character of the phase. [ABSTRACT FROM AUTHOR]

Dobrovolskyite, Na4Ca(SO4)3, is a new sulfate mineral from the Great Tolbachik fissure eruption, Kamchatka peninsula, Russia. It occurs as aggregates of tabular crystals up to 1–2 mm in maximum dimension, with abundant gas inclusions. The empirical formula calculated on the basis of O = 12 is (Na3.90K0.10)Σ4(Ca0.45Mg0.16Cu0.12Na0.10)Σ0.83S3.08O12. The crystal structure of dobrovolskyite was determined using single-crystal X-ray diffraction data as: trigonal, R3, a = 15.7223(2), c = 22.0160(5) Å, V = 4713.1(2) Å3, Z = 18 and R1 = 0.072. The Mohs' hardness is 3.5. The mineral is uniaxial (+), with ω = 1.489(2) and ɛ = 1.491(2) (λ = 589 nm). The seven strongest lines of the powder X-ray diffraction pattern [d, Å (I, %)(hkl)] are: 11.58(40)(101); 5.79(22)(202); 4.54(18)(030); 3.86(88)(033); 3.67(32)(006); 2.855(50)(306); and 2.682(100)(330). The mineral is named in honour of Prof. Dr. Vladimir Vitalievich Dolivo-Dobrovolsky (1927–2009), one of the leading Russian scientists in the field of petrology, crystal optics and crystal chemistry. The crystal structure of dobrovolskyite can be described as composed of three symmetrically independent rods running parallel to the c axis. The rods consist of six octahedral–tetrahedral [Na(SO4)6]11– or [Ca(SO4)6]10– clusters of central octahedra sharing common corners with six adjacent SO4 tetrahedra. Alternatively, the crystal structure of the mineral can be described as a 12-layer ABACABACABAC eutactic array of Na+ and Ca2+ cations, and vacancies with disordered (SO4) tetrahedra in interstices. Dobrovolskyite and similar minerals probably formed upon cooling of a high-temperature phase with disordered cation and anion arrangements. [ABSTRACT FROM AUTHOR]

The new mineral vasilseverginite, ideally Cu9O4(AsO4)2(SO4)2, was found in the Arsenatnaya fumarole at the second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with tenorite, lammerite, stranskiite, lammerite-β, langbeinite, dolerophanite, sanidine, hematite, and gahnite. Vasilseverginite occurs as prismatic crystals up to 0.02 × 0.02 × 0.06 mm3 combined in groups or interrupted crusts up to 1 × 2 cm2 in area and up to 0.1 mm thick. It is transparent, bright green, with vitreous luster. Dcalc is 4.41 g⋅cm–3. Vasilseverginite is optically biaxial (–), α 1.816(5), β 1.870(5), γ 1.897(5), estimated 2V is 30(15)°. Chemical composition (wt%, electron-microprobe) is: CuO 64.03, ZnO 0.79, Fe2O3 0.25, P2O5 0.05, As2O5 20.83, SO3 14.92, total 100.87. The empirical formula calculated on O = 20 apfu is C u 8.78 Z n 0.11 F e 0.03 3 + Σ 8.92 A s 1.98 P 0.01 S 2.03 O 20 $\left(\mathrm{Cu}_{8.78} \mathrm{Zn}_{0.11} \mathrm{Fe}_{0.03}^{3+}\right)_{\Sigma 8.92} \mathrm{As}_{1.98} \mathrm{P}_{0.01} \mathrm{~S}_{2.03} \mathrm{O}_{20}$. Vasilseverginite is monoclinic, P21/n, a = 8.1131(4), b = 9.9182(4), c = 11.0225(5) Å, β = 110.855(2)°, V = 828.84(6) Å3, and Z = 2. The strongest reflections in the powder XRD pattern [d,Å(I)(hkl)] are: 7.13(41)(101̅), 5.99(70)(110, 111̅), 5.260(100)(101), 4.642(46)(111), 3.140(31)(031̅), 2.821(35)(023̅), 2.784(38)(132̅, 032̅), 2.597(35)(204̅), and 2.556(50) (231̅, 212). The crystal structure, solved using single-crystal X‑ray diffraction data, R1 = 0.025, is based upon complex [O4Cu9]10+ layers parallel to (101̅) that are composed of edge- and corner-sharing (OCu4) tetrahedra. The topology is unprecedented in inorganic structural chemistry. The crystal structure can be considered a hybrid of the structures of popovite Cu5O2(AsO4)2 and dolerophanite Cu2O(SO4) according to the scheme Cu9O4(AsO4)2(SO4)2 = Cu5O2(AsO4)2 + 2Cu2O(SO4). The chemical hybridization does not result in a significant increase in chemical complexity of vasilseverginite compared to the sum of those of popovite and dolerophanite, whereas the structural hybridization leads to the doubling of structural information per unit cell. The mineral is named in memory of the outstanding Russian mineralogist, geologist, and chemist Vasiliy Mikhailovich Severgin (1765–1826). [ABSTRACT FROM AUTHOR]

Crystallization of the M2+[(UO2)(T6+O4)2(H2O)](H2O)4 (M2+ = Ni, Mg, Zn, Co, Fe and Mn; T6+ = S, Se) compounds is characterized by the presence of three different structure types, which are built by similar uranyl-based sulfate/selenate chains linked into pseudolayers through H-bonding networks, but the stacking sequences are different and can be described by the 1M, 2O and 2M polytypic modifications. In order to establish the interplay between chemical composition and structural architecture, eleven new Ni-bearing uranyl sulfate–selenate compounds have been synthesized, as well as a new Zn-bearing uranyl sulfate. To provide the extensive comparison of all the compounds, the crystal structures of previously studied Co and Mn uranyl sulfates of this family of compounds were re-investigated, which allowed reconsideration of their unit-cell parameters and the space-group symmetries. It is shown that crystallization of particular polytypes is governed by the interplay of the ionic radii of M2+ and T6+ cations, while pH of the initial solutions affects the rate of crystallization. [ABSTRACT FROM AUTHOR]

Flotation reagents are significant for modifying the interfacial characteristics of mineral grains to achieve the effective separation of minerals. Since the 1960s, when quantum chemistry was first introduced into the study of flotation reagents, many achievements have been made, although some controversial topics remain. The application of quantum chemistry in the research of flotation reagents for the separation of various minerals in the past decade is herein comprehensively and systematically reviewed. The main directions and gaps of current research are pointed out, the theoretical basis for the design and development of novel flotation reagents is summarized, and more importantly, the potential for the targeting design and development of efficient, selective, and environmentally friendly flotation reagent molecules by means of quantum chemistry is explored. [ABSTRACT FROM AUTHOR]

Using a statistical approach, it is demonstrated that the complexity of a crystal structure measured as the Shannon information per atom [Krivovichev (2012). Acta Cryst. A 68, 393-398] represents a negative contribution to the configurational entropy of a crystalline solid. This conclusion is in full accordance with the general agreement that information and entropy are reciprocal variables. It also agrees well with the understanding that complex structures possess lower entropies relative to their simpler counterparts. The obtained equation is consistent with the Landauer principle and points out that the information encoded in a crystal structure has a physical nature. [ABSTRACT FROM AUTHOR]