The hexagonal to cubic phase transition of Li3As was investigated at high pressure and temperature, revealing a cubic high-pressure polymorph in the Li3Bi structure type. This cubic structure type is preserved in the solid solution of Li3As-Li2Se synthesized via mechanochemical ball milling. The solid solutions were investigated via X-ray powder diffraction, showing a linear dependency of the lattice parameter a on the mole fraction of the boundary phases Li3As and Li2Se, according to Vegard's law. Configurational entropy is generated by mixed anion lattice occupation between arsenide and selenide and therefore stabilizes the cubic structure of the solid solution. At elevated temperatures, the solid solution of Li3As-Li2Se reveals an exsolution process by forming the boundary phases Li3As and Li2Se, proving the metastable character of the system. Impedance spectroscopy was used to determine the lithium-ion conductivities in the Li3As-Li2Se system, showing significantly higher conductivity values (similar to 10-4 to 10-6 S cm-1 at 50 degrees C) compared to the pure end members Li3As (similar to 10-7 S cm-1 at 50 degrees C) and Li2Se (similar to 10-7 S cm-1 at 175 degrees C).

Rb-2[TeS3] and Rb-2[TeS3] & sdot; (1)/(3) H2O were obtained from rubidium azide (RbN3), tellurium and sulfur in 2 : 1 : 3 molar ratios from evacuated fused silica ampoules at 500 degrees C under more or less anhydrous conditions. Both compounds crystallize orthorhombically in the space group P2(1)2(1)2(1) (Rb-2[TeS3]: a=873.42(6) pm, b=1316.73(9) pm, c=2064.59(14) pm; Rb-2[TeS3] & sdot; (1)/(3) H2O: a=872.97(6) pm, b=1299.82(9) pm, c=2148.26(15) pm, both at -173 degrees C for Z =12) and contain discrete psi(1)-tetrahedral [TeS3](2-) anions (d(Te-S)=232-236 pm) in layerwise arrangements. The difference results from the water of hydration in Rb-2[TeS3] & sdot; (1)/(3) H2O, which increases the coordination numbers of half of the six crystallographically distinct Rb+ cations from six and seven (only sulfur) to seven and almost eight by providing with oxygen from H2O an extra ligand (d(Rb-O)=290-318 pm). Red Rb-2[TeS3] transforms pseudo-topotactically into yellow Rb-2[TeS3] & sdot; (1)/(3) H2O immediately upon contact with moist atmosphere. Both compounds were screened with X-ray diffraction, Raman and diffuse reflectance spectroscopy as well as thermal analysis.

ObjectivesThe aim of this study was to analyze the precipitation of Cerium(III)nitrate hexahydrate [Ce(NO3)3] or Samarium(III)nitrate hexahydrate [Sm(NO3)3] solutions on human enamel with and without a salivary pellicle. Investigated parameters were At%Ce and At%Sm measured using energy dispersive x-ray spectroscopy (EDX) after test solution (two concentrations) application.Materials and methodsPrecipitation of Ce(NO3)3 and Sm(NO3)3 solutions was examined on human enamel with and without a salivary pellicle. 6 enamel specimens each were obtained from 12 freshly extracted human third molars. These specimens were ground flat and polished. A salivary pellicle was created on 3 of the 6 specimens per tooth by storing the samples in human saliva. Subsequently, an aqueous solution of Ce(NO3)3 was applied to 2 of the 6 specimens (one with, one without salivary pellicle) for 60 s. The same was carried out with an aqueous solution of Sm(NO3)3 on 2 further specimens. The remaining 2 specimens from each tooth were treated with demineralized water (negative control). Ce(NO3)3 and Sm(NO3)3 solutions were applied at 25 or 50 wt% (aqueous solutions). The test materials and concentrations were distributed using a randomization table. After 60 s exposure and rinsing with demineralized water, the elemental composition (Ce, Sm, Ca, P, O, N, Na, Mg) of the enamel surface was analyzed by EDX. Atomic percentages (At%), differences (ΔAt%) and calcium/phosphorous-ratios (Ca/P-ratios) were calculated and analyzed non-parametrically (α = 0.05).Results2.0–2.3 At%Ce (median) was detected on Ce(NO3)3-treated enamel and 0.4–0.7 At% Sm (median) was detected on Sm(NO3)3-treated enamel. Ce was only detected on the surfaces after application of Ce(NO3)3, Sm only after application of Sm(NO3)3. The Ca/P-ratio was significantly lower (1.37–1.59; p = 0.028) after the application of 25% and 50%Ce(NO3)3 as well as 50%Sm(NO3)3 compared to the control treatment (demineralized water; 1.61–1.63). After treatment with Ce(NO3)3, At%Ca and At%Na were significantly lower (p ≤ 0.043) compared to treatment with Sm(NO3)3. No significant differences were found between specimens treated with 25% or 50% lanthanide nitrate solution. Presence of a salivary pellicle had no significant influence on the measured At% with the exception of specimens treated with 50% Sm(NO3)3 with increased At%Sm (p ≤ 0.046).ConclusionsCe(NO3)3 and Sm(NO3)3 precipitate on human enamel independently of the presence of a salivary pellicle.

The new lithium arsenidotetrelates Li8SiAs4, Li8GeAs4, Li14SiAs6, Li14GeAs6 and Li14SnAs6 were synthesized via ball milling and structurally characterized by Rietveld analysis of X-ray powder diffraction data. The aliovalent substitution of lithium in hexagonal Li3As by introducing a tetravalent tetrel cation stabilizes cubic structures for Li(8)TtAs(4) (Tt = Si, Ge) in the space group Pa (3) over bar and for the lithium richer compound Li(14)TtAs(6) (Tt = Si, Ge, Sn) in the higher symmetrical space group Fm (3) over barm (no. 225). Thermal properties of the arsenidotetrelates were investigated via high temperature powder diffraction and differential thermal analysis revealing a decomposition process of the lithium richer arsenidotetrelate (Li(14)TtAs(6) -> Li(8)TtAs(4) + 2Li(3)As) into the lithium poorer arsenidotetrelates and lithium arsenide at moderate temperatures. Impedance spectroscopy shows moderate to good lithium ion conductivity for the lithium arsenidotetrelates.

Objective: To investigate the accumulation of cerium-nitrate and samarium-nitrate on dentin without or with smear-layer and to test their antibacterial activity. Design: 24 dentin-enamel slices were cut from 24 extracted molars. 12 slices underwent smear-layer creation (320 grit, 200 g, 5 s), the other 12 smear-layer removal (20 % EDTA, 300 s). Slices were halved to 48 semilunar-shaped specimens. One specimen per tooth was treated with either Ce(NO3)(3) (50 wt% aqueous solution; pH = 1.29; n = 6) or Sm(NO3)(3) (50 wt% aqueous solution; pH = 1.88; n = 6). The other specimen served as control (A. demin). After water rinsing, elemental composition (Ce, Sm, Ca, P, O, N, Na, Mg, C) was measured (EDX; EDAX Octane-Elect, APEX v2.5, low-vacuum) in dentin. Atomic percent (At%), Ca/P- and Ca/N-ratios were calculated and analyzed non-parametrically (alpha = 0.05, error rates method). Additionally, antibacterial activity (2 min exposure) of Ce(NO3)(3) and Sm(NO3)(3) against Streptococcus mutans, Actinomyces naeslundii, Schaalia odontolytica, and Enterococcus faecalis was determined (colony forming units) after anaerobic incubation at 37 degrees C for 24 h (control: 0.2 % CHX). Results: At% (median) of Ce and Sm were as follows: Ce(NO3)(3) 3.4 and 0.9 At%Ce with and without smear-layer, respectively; Sm(NO3)(3) 2.4 and 1.3 At%Sm with and without smear-layer, respectively. Ce(NO3)(3) and Sm(NO3)(3)-application significantly decreased Ca/P-ratios (1.22 - 1.45; p <= 0.02) compared to controls (1.47 - 1.63). With smear-layer, significantly higher Ca/N-ratios (5.1 - 29.3) could be detected across all groups (p <= 0.004) compared to specimens without smear-layer (0.37 - 0.48). Ce(NO3)(3) and Sm(NO3)(3) showed reduction rates of up to >= 5 log10 steps for S. mutans, A. naeslundii, and S. odontolytica. Conclusions: Cerium and samarium nitrate showed accumulation on dentin and certain antibacterial activity and could therefore be identified as potential compounds to treat and prevent dentin and root caries and dentin hypersensitivity.

Selenotetrelate compounds Na(4)TtSe(4) (Tt = Si, Ge, Sn) were synthesized by solid-state reactions. A new modification of Na4SiSe4 (Na4SiSe4-cP72), which crystallizes in the cubic space group P43n (no. 218) with a = 12.130(1) & Aring; and V = 1784.453(5) & Aring;(3), and a new modification of Na4SnSe4 (Na4SnSe4-tI216), which crystallizes in the tetragonal space group I4(1)/acd (no. 142) with a = 14.4053(4) & Aring;, c = 28.5751(8) & Aring; and V = 5929.7(3) & Aring;(3), were discovered. All of the title compounds exhibit moderate to good sodium ion conductivities, as revealed by electrochemical impedance spectroscopy. The formation reaction of Na4SiSe4 was further investigated by high-temperature X-ray powder diffraction of the ball-milled reaction mixture. Density functional-based quantum chemical calculations were performed to compare the different modifications of Na4SiSe4 and Na4SnSe4 energetically. Further modifications of Na4SiSe4 and Na4GeSe4 seem plausible, as revealed by density functional theory modeling. The stability of the hypothetic modifications was examined by phonon dispersion calculations.

The sodium tellurosilicates Na4SiTe4, Na10Si2Te9, Na6Si2Te6 and Na8Si4Te10 were synthesized by ball milling and subsequent high temperature solid state reactions and analyzed by electrochemical impedance spectroscopy. All compounds show moderate to remarkable sodium ion conductivities. The crystal structures of the novel materials Na4SiTe4 and Na10Si2Te9 were determined by X-ray diffraction. Both compounds represent new structure types with isolated SiTe4 tetrahedra. The crystal structure of Na10Si2Te9 exhibits a single telluride anion besides two SiTe4 tetrahedra. Na4SiTe4 crystallizes in the cubic space group Pa (3) over bar (no. 205) with lattice parameters a = 13.0312(1) angstrom and V = 2212.84(2) angstrom(3). Na10Si2Te9 crystallizes in the orthorhombic space group Pna2(1) (no. 33) with lattice parameters a = 12.8235(7) angstrom, b = 14.8398(8) angstrom, c = 12.9530(7) angstrom and V = 2464.9(2) angstrom(3). The presence of two different anionic units makes this compound stand out from other alkali chalcogenotetrelates. The electronic structure of all compounds was investigated by density functional theory, revealing their semiconducting behaviour.

Hydrogen storage based on the repeated reduction and oxidation (redox) reactions of iron oxide/iron composites represents a promising technology. This work is dedicated to studying the influence of the amount of water added during the pelletizing process on the cycle stability and structure of iron oxide pellets. The storage composites were prepared from iron oxide (Fe2O3) and 10 wt.-% support material (cement) with different amounts of water (18 and 33 wt.-%) in a laboratory-scale pelletizing disk. To evaluate the cycle stability of the composites, the kinetics of the redox reactions were experimentally measured at 800 °C in an atmosphere of 50% N2 and 50% H2 (reduction) or 50% steam (oxidation), respectively. Moreover, the structure of the pellets was analyzed by micro-computed tomography scans. It turned out that pellets with higher water contents attained faster kinetics and a higher cycle stability. The sample with the least water content (18 wt.-%) needed about 26 min and 19 min to reach a conversion rate of 80% during the reduction and oxidation reactions of the sixth redox cycle, respectively. In contrast, the sample with the highest water content (33 wt.-%) could achieve the same conversion rate after 18 min (reduction) and 13 min (oxidation) during the ninth redox cycle.

The 1111 compounds with an alternating sequence of fluorite and antifluorite layers serve as structural hosts for the vast family of Fe-based superconductors. Here, we use neutron powder diffraction and density-functional-theory (DFT) band-structure calculations to study magnetic order of Eu2+ in the [EuF]+ fluorite layers depending on the nature of the [TAs]- antifluorite layer that can be non-magnetic semiconducting (T = Zn), magnetic semiconducting (T = Mn), or magnetic metallic (T = Fe). Antiferromagnetic transitions at TN ~ 2.4 - 3 K due to an ordering of the Eu2+ magnetic moments were confirmed in all three EuTAsF compounds. Whereas in EuTAsF (T = Zn and Mn), the commensurate k1 = (1/2 1/2 0) stripe order pattern with magnetic moments within the ab-plane is observed, the order in EuFeAsF is incommensurate with k = (0 0.961(1) 1/2) and represents a cycloid of Eu2+ magnetic moments confined within the bc-plane. Additionally, the Mn2+ sublattice in EuMnAsF features a robust G-type antiferromagnetic order that persists at least up to room temperature, with magnetic moments along the c-direction. Although DFT calculations suggest stripe antiferromagnetic order in the Fe-sublattice of EuFeAsF as the ground state, neutron diffraction reveals no evidence of long-range magnetic order associated with Fe. We show that the frustrating interplane interaction J3 between the adjacent [EuF]+ layers is comparable with in-plane J1-J2 interactions already in the case of semiconducting fluorite layers [TAs]- (T = Zn and Mn) and becomes dominant in the case of the metallic [FeAs]- ones. The latter, along with a slight orthorhombic distortion, is proposed to be the origin of the incommensurate magnetic structure observed in EuFeAsF.

Two different polymorphs of the new selenosilicate Na4Si2Se6 were synthesized by solid-state reactions. The high-temperature polymorph Na4Si2Se6-tP24 crystallizes in the tetragonal space group P42/mcm (No. 132) with lattice parameters a = 7.2793(2) Å, c = 12.4960(4) Å, and V = 662.14(3) Å3. The main structural motifs are isolated Si2Se6 units of two edge-sharing SiSe4 tetrahedra. The high-pressure/low-temperature polymorph Na4Si2Se6-oP48 crystallizes in the orthorhombic space group Pbca (No. 61) with lattice parameters a = 12.9276(1) Å, b = 15.9324(1) Å, c = 6.0349(1) Å, and V = 1243.00(2) Å3 showing zweier single chains ∞1[Si2Se6]4-. The lattice parameters of Na4Si2Se6-tP24 were determined by single-crystal X-ray diffraction, whereas those of Na4Si2Se6-oP48 were investigated by powder X-ray diffraction. Both modifications crystallize in new structure types. An energetic comparison of the two polymorphs and further hypothetical structure types was carried out by density functional theory modeling. Calculations reveal that the polymorphs are very close in energy (ΔE = 3.4 kJ mol-1). Impedance spectroscopic measurements show ionic conductivity (σspec = 1.4 × 10-8 S cm-1 at 50 °C and 6.8 × 10-6 S cm-1 at 200 °C) with an activation energy of EA = 0.54(2) eV for Na4Si2Se6-oP48.

An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Li3AlAs2, Li3GaAs2 and Li3InAs2 were obtained from the elements via high temperature synthesis. Li3AlAs2 and Li3GaAs2 crystallize in a distorted 2.2.1 superstructure of the antifluorite structure type. The orthorhombic crystal structure is isotypic to Li(3)AIP(2) and Li3GaP2, space group Cmce (No. 64) showing layers of condensed TrAs4-tetrahedra (Tr- Al, Ga). Li3InAs2 crystallizes isotypic to Li3InP2 in a distorted 2.2.4 antifluorite type super- structure. The crystal structure is tetragonal, space group I4(1)/ acd (No. 142), showing a 3D-network of In4As10-supertetrahedra. Structural characterization by powder X-ray diffraction, thermal analysis, conductivity measurements and band structure calculations show ion conductivity for Li(3)InAs(2 )and electronic charge transport for Li3AlAs2 and Li3GaAs2.

Low charge density nanometric ions were recently shown to bind strongly to neutral hydrated matter in aqueous solution. This phenomenon, called the (super-)chaotropic effect, arises from the partial dehydration of both the nano-ion and the solute, leading to a significant gain in enthalpy. Here, we investigate the chaotropic effect of the polyoxometalate α-PW12O403− on the triblock copolymer P84: (EO)19(PO)43(EO)19 with (EO)19 the polyethoxylated and (PO)43 the polypropoxylated chains. The combination of phase diagrams, spectroscopic (nuclear magnetic resonance) and scattering (small angle neutron/X-ray scattering) techniques revealed that: (i) below the micellization temperature of P84, PW12O403− exclusively binds to the propylene oxide moiety of P84 unimers; and (ii) above the micellization temperature, PW12O403− mostly adsorbs on the ethylene oxide micellar corona. The preferential binding of the PW12O403− to the PPO chain over the PEO chains suggests that the binding is driven by the chaotropic effect and is reinforced by the hydrophobic effect. At higher temperatures, copolymer micellization leads to the displacement of PW12O403− from the PPO chain to the PEO chains. This study deepens our understanding of the subtle interplay between the chaotropic and hydrophobic effects in complex salt-organic matter solutions.

The crystal and molecular structure of three derivatives of carbonyl 2-substituted pyrroles was determined by the single crystal X-ray diffraction. There are 2,2-dichloro-1-(1-methyl-1H-pyrrol-2-yl)ethan-1-one (I), 2-chloro-1-(1H-pyrrol-2-yl)ethan-1-one (II) and methyl 1H-pyrrole-2-carboxylate (III). All compounds crystallize with one molecule in the asymmetric unit in P212121 for I and II, and P21/c group for III. Despite the similar structures of the investigated compounds, the hydrogen bonds formed in their crystal structures adopt different H-bond motifs. In structure I, the dimers R12(5) and R21(7) form a chain along the b-axis, while in structures II and III, chain C(5) structural motifs are formed. The single point calculations at a ωB97XD/6-311++G(d,p) level of theory indicate that systems with N-H⋯O bonds have greater interaction energies (are more stable) compared with systems featuring C-H⋯O/Cl bonds. A descriptive Hirshfeld analysis showed that the greatest differences are visible for the H⋯H interactions. These H⋯H interactions predominate in structure III, accounting for 45% of the intermolecular interactions, while in structures I and II, they account for only 25%. Although compounds I-II contain Cl-atoms, the percentage of Cl⋯Cl interactions is rather low. In structure with two Cl-atoms (I), the contribution of the Cl⋯Cl contacts is 8.7% and for II, the contribution accounts for only 0.4% of the interactions.

Hofmeister effects of ions in aqueous solution strongly affect chemical and biological systems. High and low charge density anions, such as SO42-and SCN- respectively, decrease (salting-out) or increase (salting in) the solubility of organic solutes in water. Due to their very low charge-density, nanometric anions, e.g. polyoxometalates (POMs), increase the solubility of organic solutes tremendously (highly salting-in) as they bind to neutral hydrated solutes strongly - a property that is attributed to the (super-)chaotropic effect. Here, we show that salting-out anions can be turned into salting-in anions in the presence of a superchaotropic POM, alpha-PW12O403-. The effect of salts composed of salting-out anions, e.g. SO42-, was investigated on the cloud point (CP) of an ethoxylated surfactant (C8E4) and a propoxylated co-solvent (C3P2) in the presence of SiW(12)O(40)(4-)and PW(12)O(40)(3-)with different counter-cations (H+, Li+, Na+, K+). SiW12O40 4-and PW(12)O(40)(3-)lead to a monotonic strong CP-increase regardless of the counterion, except for PW12O403- combined with H+. Indeed, H3PW12O40 shows a CP decrease at high POM concentrations. This peculiar behavior is attributed to the formation of large H3PW12O40-C3P2 (and H3PW12O40-C8E4) co-assemblies, as shown by SAXS. The formation of these co-assemblies results from the "bridging " effect of H+ and the lower charge density of PW12O403-compared to SiW12O404-. The addition of (basic) salting-out anions leads to (i) the consumption of H+, then to (ii) the disruption of the large H3PW12O40-C3P2 (and H3PW12O40- C8E4) co-assemblies and subsequently to (iii) a CP-increase. In the peculiar case, this shows how commonly used salting-out anions can become apparently salting-in. (C) 2022 Elsevier B.V. All rights reserved.

A physicochemical concept – called {2-phases 2-reactions 1-catalyst} – to perform two chemical reactions simultaneously with only one catalyst using a liquid–liquid biphasic system is established.

Researchers carrying out calculations using the DFT method face the problem of the correct choice of the exchange-correlation functional to describe the quantities they are interested in. This article deals with benchmark calculations aimed at testing various exchange-correlation functionals in terms of a reliable description of the electron density distribution in molecules. For this purpose, 30 functionals representing all rungs of Jacob’s Ladder are selected and then the values of some QTAIM-based parameters are compared with their reference equivalents obtained at the CCSD/aug-cc-pVTZ level of theory. The presented results show that the DFT method undoubtedly has the greatest problems with a reliable description of the electron density distribution in multiple strongly polar bonds, such as C=O, and bonds associated with large electron charge delocalization. The performance of the tested functionals turned out to be unsystematic. Nevertheless, in terms of a reliable general description of QTAIM-based parameters, the M11, SVWN, BHHLYP, M06-HF, and, to a slightly lesser extent, also BLYP, B3LYP, and X3LYP functionals turned out to be the worst. It is alarming to find the most popular B3LYP functional in this group. On the other hand, in the case of the electron density at the bond critical point, being the most important QTAIM-based parameter, the M06-HF functional is especially discouraged due to the very poor description of the C=O bond. On the contrary, the VSXC, M06-L, SOGGA11-X, M06-2X, MN12-SX, and, to a slightly lesser extent, also TPSS, TPSSh, and B1B95 perform well in this respect. Particularly noteworthy is the overwhelming performance of double hybrids in terms of reliable values of bond delocalization indices. The results show that there is no clear improvement in the reliability of describing the electron density distribution with climbing Jacob’s Ladder, as top-ranked double hybrids are also, in some cases, able to produce poor values compared to CCSD.

Phase pure Li3As and Li3P were synthesized from the elements by a high temperature route. Crystal structures were refined from powder X-ray diffraction data. The title compounds were further characterized by difference thermal analysis, temperature dependent X-ray powder diffraction and impedance spectroscopy, proving unexpected Li ion conductivity for Li3As. High pressure behaviour of the title compounds was modeled via density functional theory, confirming the experimentally reported cubic modifications of Li3P and Li3As.