Anion Ordering Research Articles

Anion Ordering in Bichalcogenides

This review contains recent developments and new insights in the research on inorganic, crystalline compounds with two different chalcogenide ions (bichalcogenides). Anion ordering is used as a parameter to form structural dimensionalities as well as local- and global-electric polarities. The reason for the electric polarity is that, in the heterogeneous bichalcogenide lattice, the individual bond-lengths between cations and anions are different from those in a homogeneous anion lattice. It is also shown that heteroleptic tetrahedral and octahedral coordinations offer a multitude of new crystal fields and coordinations for involved cations. This coordination diversity in bichalcogenides seems to be one way to surpass electro-chemical redox potentials: three oxidation states of a single transition metal can be stabilized, e.g., Ba15V12S34O3. A new type of disproportionation, related to coordination, is presented and results from chemical pressure on the bichalcogenide lattices of (La,Ce)CrS2O, transforming doubly [CrS3/3S2/2O1/1]3− (5+1) into singly [CrS4/2S2/3]7/3− (6+0) and [CrS4/3O2/1]11/3− (4+2) coordinations. Also, magnetic anisotropy is imposed by the anion ordering in BaCoSO, where magnetic interactions via S or O occur along two different crystallographic directions. Further, the potential of the anion lattice is discussed as a parameter for future materials design.

High‐Pressure Synthesis of Manganese Oxyhydride with Partial Anion Order

AbstractThe high‐pressure synthesis of a manganese oxyhydride LaSrMnO3.3H0.7 is reported. Neutron and X‐ray Rietveld analyses showed that this compound adopts the K2NiF4 structure with hydride ions positioned exclusively at the equatorial site. This result makes a striking contrast to topochemical reductions of LaSrMnO4 that result in only oxygen‐deficient phases down to LaSrMnO3.5. This suggests that high H2 pressure plays a key role in stabilizing the oxyhydride phase, offering an opportunity to synthesize other transition‐metal oxyhydrides. Magnetic susceptibility revealed a spin‐glass transition at 24 K that is due to competing ferromagnetic (Mn2+–Mn3+) and antiferromagnetic (Mn2+–Mn2, Mn3+–Mn3+) interactions.

High-Pressure Synthesis of Manganese Oxyhydride with Partial Anion Order.

The high-pressure synthesis of a manganese oxyhydride LaSrMnO3.3 H0.7 is reported. Neutron and X-ray Rietveld analyses showed that this compound adopts the K2 NiF4 structure with hydride ions positioned exclusively at the equatorial site. This result makes a striking contrast to topochemical reductions of LaSrMnO4 that result in only oxygen-deficient phases down to LaSrMnO3.5 . This suggests that high H2 pressure plays a key role in stabilizing the oxyhydride phase, offering an opportunity to synthesize other transition-metal oxyhydrides. Magnetic susceptibility revealed a spin-glass transition at 24 K that is due to competing ferromagnetic (Mn(2+) -Mn(3+) ) and antiferromagnetic (Mn(2+) -Mn(2) , Mn(3+) -Mn(3+) ) interactions.

ChemInform Abstract: Anionic Ordering in Ba15V12S34O3, Affording Three Oxidation States of Vanadium and a Quasi‐One‐Dimensional Magnetic Lattice.

AbstractPolycrystalline Ba15V12S34O3 is prepared by solid state reaction of a 12:3:12:22 molar mixture of BaS, BaO, V, and S under 200 mbar Ar (corundum crucible in sealed quartz tube, 1.

Qualitative spring water management in the central western catchment of the West Bank from hydrochemical and environmental isotopes approaches

This study assesses spring water quality data connected to groundwater pollution indicators for building a qualitative groundwater management system in the central western catchment of the West Bank. It characterizes the major ion chemistry and trace elements for the mountainous spring water in terms of their suitability for irrigation and domestic purposes. The results increase community awareness about qualitative access to available and reliable water resources in central catchments. The cation–anion orders indicate calcium–hydrogen carbonate spring water type, useful for determining the parameters of risk. EC-TDS relations classified the water as fresh and within the allowable limits of the WHO guidelines. The fact that the majority of these springs are located within densely populated areas explains the higher counts of total and fecal coliforms. The environment of recharge is determined through the stable isotopic compositions of deuterium and oxygen—18 of a north–south profile analysis. The study shows that the isotopic composition, ranging from −5.06 to −5.89 ‰ for δ18O and from −20.28 to −24.44 ‰ for δ2H. The δ2H–δ18O relationship is used to define the local meteoric water line (LMWL), according to the equation: δ2H = 4.7 δ18O + 3.6. The plotted isotopic content of the analyzed water samples on the Mediterranean meteoric water line signifies water recharge from recent precipitation.

Production of glycerol carbonate from glycerol with aid of ionic liquid as catalyst

The rapid growth of biodiesel industry has led to a large surplus of its major unintentional byproduct particularly glycerol. Thus, finding a new application is necessary to convert glycerol to value added products. In this study, glycerol has been subjected to a transesterification reaction to synthesis glycerol carbonate (GC) over several selected ammonium and imidazolium-based ionic liquids (ILs) as catalysts. It is believed that the variation of catalytic performance between ILs was due to the anion strength of ILs. The glycerol conversion, yield and selectivity of GC were followed the anion order of [Ac]>[Dca]>[Fmt]>[DMP]>[NO3]>[Cl]>[BF4]. Effects of reaction temperature, time, diethyl carbonate (DEC)/glycerol molar ratio and catalyst loading on glycerol conversion and GC yield have been analysed. The IL, 1-ethyl-3-methylimidazolium acetate (emim[Ac]) shows best performance under solvent-free with conversion of glycerol and GC yield reached highest at 93.50% and 88.70%, respectively under reaction temperature of 120°C reaction time of 2h, DEC/glycerol molar ratio of 2 and catalyst loading of 0.5mol%. Also, this emim[Ac] can be reused as catalyst at least three times without any significant reduction in conversion, yield and selectivity. Reaction mechanism of the transesterification reaction catalysed by emim[Ac] has been proposed in this study.

Phase transition to the Fulde–Ferrell–Larkin–Ovchinnikov state in a quasi-one-dimensional organic superconductor with anion order

A theoretical study is presented on the effect of anion order on the phase transition from the normal state to a Fulde–Ferrell–Larkin –Ovchinnikov superconducting state in a quasi-one-dimensional organic superconductor (TMTSF)2ClO4. The temperature dependence of the upper critical field Hc2(T) is examined. In the absence of anion order, the Hc2(T) curve exhibits a one- to two-dimensional crossover with decreasing temperature T. For a sufficiently large anion order parameter, the dimensional crossover disappears and then a kink appears in the Hc2(T) curve.

Phases of Anionic Ordering in Elpasolite Structures (Ordered Perovskites

Phases of Anionic Ordering in Elpasolite Structures (Ordered Perovskites

Ferroelectric Response Induced in cis-Type Anion Ordered SrTaO2N Oxynitride Perovskite

Oxynitride perovskite SrTaO2N has been attracting attention as a possible new dielectric material owing to the cis-type anion ordering in its crystal structure. It is currently difficult to obtain it in bulk form because it easily loses a part of its nitrogen to become semiconducting during densification at high temperature. We found that its surface layer recovered its original orange color and dielectric properties after postannealing in ammonia. Piezoresponse force microscopy measurements clearly revealed a ferroelectric behavior on the entire orange surface layer peeled off from the black sintered body inside. The present sample was free-standing at about 8 μm thick and clearly distinct from the compressively strained SrTaO2N thin films for which ferroelectricity was recently reported in small domains (10–102 nm) in the locally assumed trans-type anion ordering. The present results represent the first experimental observation of ferroelectric response in a bulk oxynitride perovskite with cis-type anio...

Anion order in perovskites: a group-theoretical analysis.

Anion ordering in the structure of cubic perovskite has been investigated by the group-theoretical method. The possibility of the existence of 261 ordered low-symmetry structures, each with a unique space-group symmetry, is established. These results include five binary and 14 ternary anion superstructures. The 261 idealized anion-ordered perovskite structures are considered as aristotypes, giving rise to different derivatives. The structures of these derivatives are formed by tilting of BO6 octahedra, distortions caused by the cooperative Jahn-Teller effect and other physical effects. Some derivatives of aristotypes exist as real substances, and some as virtual ones. A classification of aristotypes of anion superstructures in perovskite is proposed: the AX class (the simultaneous ordering of A cations and anions in cubic perovskite structure), the BX class (the simultaneous ordering of B cations and anions) and the X class (the ordering of anions only in cubic perovskite structure). In most perovskites anion ordering is accompanied by cation ordering. Therefore, the main classes of anion order in perovskites are the AX and BX classes. The calculated structures of some anion superstructures are reported. Comparison of predictions and experimentally investigated anion superstructures shows coherency of theoretical and experimental results.

Crystallographic analysis of modular structures of cupromakopavonite Cu8Ag3Pb4Bi19S38 and heyrovskyite Pb6Bi2S9 minerals

The well-known “modular” concept of the structure of two complex sulfides has been supplemented by crystallographic analysis fixing specific features of ordering atomic sites in crystal structures. Regular ordering of cations (formation of F sublattices with close parameters) and independent, less regular ordering of anions is established. It is shown that local ordering of atoms in contacting modular layers gives rise to a unified sublattice for the structures and forms a long-range order.

Observation of Anion Order in Pb2Ti4O9F2.

The observation of anion order is indispensable for the investigation of oxyfluorides. However, the negligible contrast between O(2-) and F(-) in both X-ray and neutron diffraction obscures the distinct anion sites for Rietveld refinement. Therefore, the difference in the chemical bonding of M-O(2-) and M-F(-) is the key to determining anion order. In this study, bond-valence-sum calculations and determination of the electron density distribution by the maximum entropy method illustrated anion order in the newly synthesized oxyfluoride Pb2Ti4O9F2. These results demonstrate a promising method to determine anion order in mixed anion systems.

Structure property relationships arising from anion order in solid oxynitrides

Structure property relationships arising from anion order in solid oxynitrides

Communication: Salt-induced water orientation at a surface of non-ionic surfactant in relation to a mechanism of Hofmeister effect.

The behavior of water molecules at the surface of nonionic surfactant (monomyristolein) and effects of monovalent ions on the behavior are investigated using the heterodyne-detected vibrational sum frequency generation spectroscopy. It is found that water molecules at the surface are oriented with their hydrogen atoms pointing to the bulk, and that the degree of orientation depends on the anion strongly but weakly on the cation. With measured surface potentials in those saline solutions, it is concluded that the heterogeneous distribution of anions and cations in combination with the nonionic surfactant causes the water orientation. This heterogeneous distribution well explains the contrasting order of anions and cations with respect to the ion size in the Hofmeister series.

Phase transitions of cesium azide at pressures up to 30 GPa studied using in situ Raman spectroscopy

Cesium azide has been studied by Raman spectroscopy at pressures up to ≈30 GPa at room temperature. The sequence of phase transitions to Phase III (at 0.5 GPa), Phase IV (at 4.3 GPa), and Phase V (at ≈19 GPa) has been observed in agreement with recent X-ray diffraction studies. Phase III has been found to adopt a monoclinic C2/m structure with two azide anions in nonequivalent positions, where one set of azide anions appears to be orientationally disordered according to the observed Raman spectra. The transition to Phase IV has been associated with orientational ordering of azide anions, while the transition to Phase V has been shown to proceed with a lowering of crystal symmetry. Moreover, spectroscopic features indicate a possible change of bonding in CsN3 toward formation of covalent bonds at high pressures.

Hydrogeochemistry of Dal Lake and the potential for present, future management by using facies, ionic ratios, and statistical analysis

This paper presents the inventory study on the Dal Lake, the second largest fresh water lake in Kashmir Valley, India. A total of 336 water samples were monthly collected to assess the present scenario of weathering and anthropogenic impact on water for hydrological year (2012–2013). The results showed a significant spatio-temporal (monthly and basinal) variability in the concentration of the physical and chemical characteristics (major ions) of the lake water. The lake water is alkaline in nature (pH: 7.1–8.7) characterized by medium total dissolved solids of 80.8–230.7 mg L−1 and electrical conductivity of 126.3–384.6 µs cm−1. The order of major cations and anions is Ca2+ > Mg2+ > Na+ > K+ and HCO3 > SO42− > Cl− > NO3−, respectively. The geochemical processes suggested that the lake water composition is mostly influenced by the lithology of the catchment. Ca–Mg–HCO3 was found to be the dominant hydrochemical facies followed by mixed type of water (throughout the hydrological year). From sub-basin point of view all the four basins show Ca–Mg–HCO3 type water, but Hazratbal and Nigeen basins also show shift towards SO4 and Cl type of water reflecting the anthropogenic inputs in these two basins. Basin wise the average concentration of Ca2+, Mg2+, HCO3−, Cl−, and NO3− were highest in Nigeen basin due to high resistance time of water within the basin and Na+, K+, and SO42− in Hazratbal basin from the silicate weathering, and sewage plant sources. The Gagribal basin showed lowest values of Ca2+, Na+, K+, HCO3−, and Cl−, whereas Boddal and Hazratbal basin showed lowest values of SO42−, NO3−, and Mg2+, respectively. On monthly basis Ca2+, Na+, K+, and HCO3− were highest in April, Mg2+, and NO3− in January, Cl− in December and SO42− in September, lower value of Ca2+, and Cl− were observed in July, Mg2+ in April and HCO3−, and K+ in August. The study suggested that the predominant processes influencing water chemistry were congruent carbonate dissolution (61.9 %) and incongruent silicate weathering (12.7 %) and cation exchange of Na+ in rocks for Ca2+ and Mg2+ (10 %). The high major-ion concentrations indicated long water–rock interactions and long residence time of water in the lake. The higher concentrations SO42−, NO3− and Cl− reflect anthropogenic inputs from the immediate catchment.

Electronic instabilities and irradiation effects in the (TMTTF)2X series

The paper presents a single-crystal ESR study of a series of pristine and X-ray irradiated (TMTTF)2X salts, where TMTTF is tetramethyltetrathiafulvalene and X is either a centro-symmetrical (SbF6 and Br) or a non-centro-symmetrical (ReO4, ClO4, BF4, SCN and NO3) monovalent anion. Besides standard line-width and spin-susceptibility measurements, the analysis of the asymmetry of the ESR line shape allows to obtain simultaneous information on the electrical conductivity. This whole set of data is used to determine the charge and spin gaps related to the charge ordering (CO) and anion ordering (AO) ground states and their evolution as a function of X-ray irradiation damages. We show in particular that the sensibility of (TMTTF)2X salts to irradiation depends upon the nature of the anion X and that the CO ground state is drastically affected by irradiation damages at the difference of the AO ground state. We also present evidence of a CO transition and of a decoupling between the AO transition and the opening of a spin gap in (TMTTF)2NO3.

Effects of feed solution chemistry on low pressure reverse osmosis filtration of cesium and strontium

The objective of this study was to identify the removal mechanisms of radionuclides by reverse osmosis (RO) membranes under conditions relevant to full-scale water treatment. For this purpose, the effects of feed solution chemistry on the removal of Cs and Sr by a low pressure RO system was investigated by systematically varying membrane surface charge, ionic composition, and organic matter concentrations. The results showed that the effects of solution chemistry on the filtration of Cs and Sr were related to their hydrated ionic radius, resulting in the predominance of the Donnan’s effect and electrostatic interactions, respectively. Consequently, the rejection of Cs increased more pronouncedly than Sr with the increases of feed concentration. Due to the Donnan’s effect, different anions decreased the rejection of Cs to different extents in accordance to the order of anions’ radii as SO42−>Cl−>NO3−>F−. The variations in Sr rejection were influenced by the electrostatic interactions between Sr2+ and the membrane. In addition, humic acid (HA) lowered the rejection of Cs and caused significant membrane flux decline, but did not change the rejection of Sr. Sr also aggravated HA fouling of the membrane.

Structural and magnetic properties of RTiNO2 (R=Ce, Pr, Nd) perovskite nitride oxides

Neutron powder diffraction indicates that CeTiNO2 and PrTiNO2 crystallize with orthorhombic Pnma symmetry (Ce: a=5.5580(5), b=7.8369(7), and c=5.5830(4)Å; Pr: a=5.5468(5), b=7.8142(5), and c=5.5514(5)Å) as a result of a–b+a– tilting of the titanium-centered octahedra. Careful examination of the NPD data, confirms the absence of long range anion order in both compounds, while apparent superstructure reflections seen in electron diffraction patterns provide evidence for short range anion order. Inverse magnetic susceptibility plots reveal that the RTiNO2 (R=Ce, Pr, Nd) compounds are paramagnetic with Weiss constants that vary from −28 to −42K. Effective magnetic moments for RTiNO2 (R=Ce, Pr, Nd) are 2.43μB, 3.63μB, and 3.47μB, respectively, in line with values expected for free rare-earth ions. Deviations from Curie–Weiss behavior that occur below 150K for CeTiNO2 and below 30K for NdTiNO2 are driven by magnetic anisotropy, spin–orbit coupling, and crystal field effects.

Effects of specific anions on the relationship between the ion-adsorption properties of sulfobetaine gel and its swelling behavior

The adsorption of cations and anions from four different halide solutions, i.e., KF, KCl, KBr, and KI solutions, onto N,N-dimethyl(acrylamidopropyl)ammonium propane sulfonate (DMAAPS) gels prepared using various cross-linker concentrations was investigated at a variety of temperatures; the swelling degrees of the gel in these solutions were also examined. The amount of K+ adsorbed coincided with the adsorption of the anions (i.e., I−, Br−, Cl−, or F−) because of simultaneous adsorption of the cations and anions onto DMAAPS gel. The order of anions, which gave larger amount of K+ adsorbed onto the gel, was opposite that of the Hofmeister series, i.e., I− > Br− > Cl− > F−. Furthermore, the relationship between the degree of swelling of the gel and amount of K+ adsorbed onto the gel was elucidated. The data points laid on the same line for the same halide solution even at different cross-linker concentrations or temperatures. At smaller degrees of swelling, the amount of K+ adsorbed remained unchanged and then decreased gradually as the degree of swelling increased. In solutions containing anions with lower hydration ability, such as KI, the amount of K+ adsorbed decreased at larger degrees of swelling. In contrast, in solutions containing anions with higher hydration abilities, such as KCl, the adsorbed amount of K+ decreased at smaller degrees of swelling. Additionally, it was found that, in mixtures of these halide solutions, competitive adsorption of anions occurred. Anions with lower hydration abilities adsorbed more readily in the mixtures than in the single-anion solution. In contrast, anions with higher hydration abilities adsorbed less readily in the mixtures than in the single-anion solution.