We Are Never Ever Getting (back to) Ideal Symmetry: Structure and Luminescence in a Ten-Coordinated Europium(III) Sulfate Crystal

Our theoretical treatment of electronic structure in coordination complexes often rests on assumptions of symmetry. Experiments rarely provide fully symmetric systems to study. In solution, fluctuation in solvation, variations in conformation, and even changes in constitution occur and complicates the picture. In crystals, lattice distortion, energy transfer, and phonon quenching is in play, but we are able to have distinct symmetries. Yet the question remains: How is the real symmetry in a crystal compared to ideal symmetries? Moreover, at what level of detail do we need to study a system to determine, if the electronic structure behaves as if it has ideal symmetry? Here, we have revisited the Continues Shape Measurement (CShM) approach developed by Ruiz-Martínez and Alvarez to evaluate the structure of ten-coordinated europium(III) ions in a K5Na[Eu2(SO4)6] structure. By comparing the result of the symmetry deviation analysis to luminescence data, we are able to show the effect of small deviations from ideal symmetry. We suggest using a symmetry deviation value, σideal, determined by using our updated approach to Continues Shape Measurements, where we also align the structure via our AlignIt code. AlignIt includes normalization and relative orientation in the symmetry comparison, and by combining the calculated values with the experimentally determined energy level splitting, we were able create the first point on a scale that can show how close to ideal an experimental structure actually is.

In-situ Confocal Laser Microscopy Study of Lead Sulfate Crystal Growth on Negative Electrode of Lead-acid Batteries

Confocal Laser Scanning Microscopy (CLSM) is a widely used technique mainly in fields of biology or multidisciplinary material sciences. Although CLSM has the ability to monitor also electrochemical processes like lead sulfate-crystal growth, nobody used CLSM for such application. We performed operando observation of the pasted active mass of negative electrode for lead-acid batteries during deep cycling. Electrode with pasted negative active mass was optimized for cycling in ECC-opto-std electrochemical cell by EL-CELL. Lead sulfate crystal growth and changes of electrode surface during cycling were observed using a laser scanning confocal microscope Olympus Lext OLS4100. We evaluate the surface changes and sulfate crystal growth. The cycling mode leads to fast gradual degradation of the negative electrode and massive growth of lead sulfate crystals. Confocal laser scanning microscopy was identified as a powerful technique for visualization of lead sulfate crystal promotion during battery cycling.

Seeds of imperfection rule the mesocrystalline disorder in natural anhydrite single crystals

In recent years, we have come to appreciate the astounding intricacies associated with the formation of minerals from ions in aqueous solutions. In this context, a number of studies have revealed that the nucleation of calcium sulfate systems occurs nonclassically, involving the aggregation and reorganization of nanosized prenucleation species. In recent work, we have shown that this particle-mediated nucleation pathway is actually imprinted in the resultant micrometer-sized CaSO4 crystals. This property of CaSO4 minerals provides us with the unique opportunity to search for evidence of nonclassical nucleation pathways in geological environments. In particular, we focused on large anhydrite crystals extracted from the Naica Mine in Mexico. We were able to shed light on this mineral's growth history by mapping defects at different length scales. Based on this, we argue that the nanoscale misalignment of the structural subunits, observed in the initial calcium sulfate crystal seeds, propagates through different length scales both in morphological, as well as in strictly crystallographic aspects, eventually causing the formation of large mesostructured single crystals of anhydrite. Hence, the nonclassical nucleation mechanism introduces a “seed of imperfection,” which leads to a macroscopic “single” crystal whose fragments do not fit together at different length scales in a self-similar manner. Consequently, anisotropic voids of various sizes are formed with very well-defined walls/edges. However, at the same time, the material retains in part its single crystal nature.

Об изотропных точках в примесных кристаллах K-=SUB=-2-=/SUB=-SO-=SUB=-4-=/SUB=-

The temperature, spectral and pressure dependences of the birefringence Δni of potassium sulfate crystals doped with 1.7% of copper have been studied. The introduction of the impurity is found to change the absolute value of Δni and lead to an increase in the temperature dependence of Δnі(Т). It is shown that the isotropic points appear in the doped crystal of potassium sulfate, and are shifted, compared with a pure crystal, towards low temperatures by 5 K and 11 K, respectively. It was established, that uniaxial stresses change the magnitude of the Δni absolute values, as well as the region of existence of the isotropic state. Generalized temperature-spectral-baric diagrams of the isotropic state of doped potassium sulfate crystal are constructed, making it possible to use them as a crystal-optical sensor.

Switchable Phase Transition of Sodium Sulfate Crystal Activated by Shock Waves

According to the available sources obtained from the literature survey to date, shock wave induced switchable phase transition is yet to be understood concretely as compared to the irreversible phase...

Sulfates from the Pyrite Ore Deposits of the Apuan Alps (Tuscany, Italy): A Review

The occurrence of sulfate minerals associated with the pyrite ores of the southern Apuan Alps has been known since the 19th century but modern mineralogical studies started only in the last decade. Sulfate assemblages were identified in all the pyrite ore deposits from the studied area but the more impressive associations were discovered in the Fornovolasco and Monte Arsiccio mines. Their study allowed to improve the knowledge of the sulfate crystal-chemistry and to achieve a better understanding of the acid mine drainage (AMD) systems associated with pyrite oxidation. More than 20 different mineral species were identified and, among them, four sulfates (volaschioite, giacovazzoite, magnanelliite, and scordariite) have their type localities in the pyrite ore deposits of the Apuan Alps. A review of the mineralogical results of a ten-year-long study is given here.

Inhibition of Poly(ethylenediaminetetraacetic acid-diethanolamine) on Deposition of Calcium Sulfate Crystal in Simulated Industrial Water

Calcium sulfate scale is a typical deposit on the equipment pieces or pipes of an industrial water system. Scale inhibitors could obviously reduce the precipitation of calcium sulfate crystal. The development and research of late-model environmentally friendly polymer inhibitors are often urgent problems to be addressed. A water-soluble poly(ethylenediaminetetraacetic acid-diethanolamine) (PEDTA-DEA) was successfully synthesized by thermal polycondensation of ethylenediaminetetraacetic acid (EDTA) with diethanolamine (DEA). The polymer product was characterized by Fourier infrared spectrum (FTIR) and the molecular weight was measured by gel chromatography, which confirms the polymerization of the two monomers. The inhibition effect of the polymer against calcium sulfate deposition was studied by static scale inhibition tests. When the Ca2+ concentration is 3000 mg/L, and the dosage of the polymer inhibitor is 10 mg/L, the inhibition effect exceeds 90%. The results show that PEDTA-DEA can inhibit the precipitation of calcium sulfate and reduce the deposition of calcium sulfate scale. The precipitate of calcium sulfate collected from the static scale inhibition test solution was analyzed by FTIR, scanning electron microscope (SEM) and X-ray diffraction (XRD). The results revealed that the addition of the polymer significantly changes the calcium sulfate crystal’s growth shape. Therefore, PEDTA-DEA is a potential calcium sulfate precipitation inhibitor for the industrial water system.