The Thermodynamics of Selenium Minerals in Near-Surface Environments

Кривовичев, В. Г.; Charykova, M. V.; Vishnevskiy, A. V.

doi:10.3390/min7100188

Cited by 22 publications

(16 citation statements)

References 49 publications

(62 reference statements)

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“…Analogously, the crystal structures of synthetic uranyl chromates [67,68] and molybdates [69], which are isotypic to that one of demesmaekerite, were obtained at hydrothermal conditions (above 120 • C) or solid state reactions (at 300 • C). Nevertheless, based on laboratory [91,92] and field observations, namely of the mineral association from Zálesí (Czech Republic) [8], it is clear that demesmaekerite and piretite (and several other unnamed or poorly identified U-Se phases) formed as a result of supergene alteration processes, which exclude hydrothermal activity. These observations are supported by the radioanalytical dating of demesmaekerite.…”

Section: Discussionmentioning

confidence: 99%

Crystal Chemistry and Structural Complexity of Natural and Synthetic Uranyl Selenites

et al. 2019

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Comparison of the natural and synthetic phases allows an overview to be made and even an understanding of the crystal growth processes and mechanisms of the particular crystal structure formation. Thus, in this work, we review the crystal chemistry of the family of uranyl selenite compounds, paying special attention to the pathways of synthesis and topological analysis of the known crystal structures. Comparison of the isotypic natural and synthetic uranyl-bearing compounds suggests that uranyl selenite mineral formation requires heating, which most likely can be attributed to the radioactive decay. Structural complexity studies revealed that the majority of synthetic compounds have the topological symmetry of uranyl selenite building blocks equal to the structural symmetry, which means that the highest symmetry of uranyl complexes is preserved regardless of the interstitial filling of the structures. Whereas the real symmetry of U-Se complexes in the structures of minerals is lower than their topological symmetry, which means that interstitial cations and H 2 O molecules significantly affect the structural architecture of natural compounds. At the same time, structural complexity parameters for the whole structure are usually higher for the minerals than those for the synthetic compounds of a similar or close organization, which probably indicates the preferred existence of such natural-born architectures. In addition, the reexamination of the crystal structures of two uranyl selenite minerals guilleminite and demesmaekerite is reported. As a result of the single crystal X-ray diffraction analysis of demesmaekerite, Pb 2 Cu 5 [(UO 2 ) 2 (SeO 3 ) 6 (OH) 6 ](H 2 O) 2 , the H atoms positions belonging to the interstitial H 2 O molecules were assigned. The refinement of the guilleminite crystal structure allowed the determination of an additional site arranged within the void of the interlayer space and occupied by an H 2 O molecule, which suggests the formula of guilleminite to be written as Ba 3 . occurrence is limited to just a few localities. First, these are Musonoi and Shinkolobwe mines in DR Congo [6], two of the minerals were only found in the Repete mine (San Juan County, Utah, USA) [5], and a few more occurrences in Europe could be mentioned (small uranium deposit Zálesí in the Czech Republic, Liauzun in France, and La Creusaz U prospect in Switzerland) [8]. Nevertheless, apart from mineralogy, uranyl selenites are of great interest from the geochemical and radiochemical points of view. It is known that fission products contain 53 g per ton [9] of long-lived 79 Se isotope with a half-life of 1.1 × 10 6 years [10] after three years of nuclear fuel irradiation in the reactor. Thus, an understanding of the processes of mineral formation in nature and their synthetic analogs in laboratories can help in the processing of nuclear wastes. Crystal chemical and structural investigations are key points in such a material's scientific studies due to the essential knowledge of how the variation in the chemical composi...

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Section: Discussionmentioning

confidence: 99%

Crystal Chemistry and Structural Complexity of Natural and Synthetic Uranyl Selenites

et al. 2019

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“…Previously, we have characterized Se oxysalts (selenites and selenates) and evaluated the accuracies of thermodynamic constants of selenides and selenites [40,41]. The aim of this paper is to characterize Se minerals as natural mineral systems and to investigate relations between their chemical and structural complexities, measured as Shannon information amounts, and to apply these measures to the understanding Se minerals diversity and complexity.…”

Section: Introductionmentioning

confidence: 99%

Selenium Minerals: Structural and Chemical Diversity and Complexity

2019

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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).

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“…Another interesting feature of the crystal structure is the existence of empty cavities in the structure (see Figure 1c), which are related to presence of Se lone pair of electrons. After the accurate determination of the crystal structure, most studies of chalcomenite have been focused on its lattice vibrations [6,7] and thermophysical and thermochemical properties [8,9]. All of these studies have been carried out at ambient pressure.…”

Section: Introductionmentioning

confidence: 99%

A High-Pressure Investigation of the Synthetic Analogue of Chalcomenite, CuSeO3∙2H2O

et al. 2019

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Synthetic chalcomenite-type cupric selenite CuSeO3∙2H2O has been studied at room temperature under compression up to pressures of 8 GPa by means of single-crystal X-ray diffraction, Raman spectroscopy, and density-functional theory. According to X-ray diffraction, the orthorhombic phase undergoes an isostructural phase transition at 4.0(5) GPa with the thermodynamic character being first-order. This conclusion is supported by Raman spectroscopy studies that have detected the phase transition at 4.5(2) GPa and by the first-principles computing simulations. The structure solution at different pressures has provided information on the change with pressure of unit–cell parameters as well as on the bond and polyhedral compressibility. A Birch–Murnaghan equation of state has been fitted to the unit–cell volume data. We found that chalcomenite is highly compressible with a bulk modulus of 42–49 GPa. The possible mechanism driving changes in the crystal structure is discussed, being the behavior of CuSeO3∙2H2O mainly dominated by the large compressibility of the coordination polyhedron of Cu. On top of that, an assignation of Raman modes is proposed based upon density-functional theory and the pressure dependence of Raman modes discussed. Finally, the pressure dependence of phonon frequencies experimentally determined is also reported.

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The Thermodynamics of Selenium Minerals in Near-Surface Environments

Cited by 22 publications

References 49 publications

Crystal Chemistry and Structural Complexity of Natural and Synthetic Uranyl Selenites

Crystal Chemistry and Structural Complexity of Natural and Synthetic Uranyl Selenites

Selenium Minerals: Structural and Chemical Diversity and Complexity

A High-Pressure Investigation of the Synthetic Analogue of Chalcomenite, CuSeO3∙2H2O

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