Cation Ordering Research Articles

Zipper‐Like Dynamic Switching of Coordination Bonds Gives a Polar Bimetallic Halide Toward Self‐Driven X‐Ray Detection

AbstractPolar molecular crystals hold a promise for controlling bulk physical properties originated in their unique switchable polarity via structural transformation. However, the mechanisms for switching polarization are mainly limited to displacive and disorder‐order phase transitions, which rarely involve the reconstruction of chemical bonds. Here, we have switched and tuned electric polarization in a bimetallic halide, (Neopentylammonium)4AgBiBr8 (1), as verified by light‐excited pyroelectric effect. Most notably, its Ag−Br coordination bonds show a zipper‐like dynamic switching behavior from the ‘locked’ to ‘unlocked’ state, namely, reconstruction of chemical bonds. Coupling with the dynamic ordering of organic cations, this bond‐switching transition makes a contribution to switchable polarization of 1. As expected, its polarity creates pyroelectric effect for self‐driven X‐ray detection with high sensitivity (3.8×103 μC Gy−1 cm−2) and low limit of detection (4.8 nGy s−1). This work on the bond‐switching mechanism provides an avenue to design polar molecular candidate for smart optoelectronic devices.

Zipper-Like Dynamic Switching of Coordination Bonds Gives a Polar Bimetallic Halide Toward Self-Driven X-Ray Detection.

Polar molecular crystals hold a promise for controlling bulk physical properties originated in their unique switchable polarity via structural transformation. However, the mechanisms for switching polarization are mainly limited to displacive and disorder-order phase transitions, which rarely involve the reconstruction of chemical bonds. Here, we have switched and tuned electric polarization in a bimetallic halide, (Neopentylammonium)4AgBiBr8 (1), as verified by light-excited pyroelectric effect. Most notably, its Ag-Br coordination bonds show a zipper-like dynamic switching behavior from the 'locked' to 'unlocked' state, namely, reconstruction of chemical bonds. Coupling with the dynamic ordering of organic cations, this bond-switching transition makes a contribution to switchable polarization of 1. As expected, its polarity creates pyroelectric effect for self-driven X-ray detection with high sensitivity (3.8×103 μC Gy-1 cm-2) and low limit of detection (4.8 nGy s-1). This work on the bond-switching mechanism provides an avenue to design polar molecular candidate for smart optoelectronic devices.

Compositions of the major ions, variations in their sources, and a risk assessment of the Qingshuijiang River Basin in Southwest China: a 10-year comparison of hydrochemical measurements.

Rivers in karst areas face increased risks from persistent growth in human activity that leads to changes in water chemistry and threatens the water environment. In this study, principal component analysis (PCA), ion ratio measurements, and other methods were used to study the water chemistry of the Qingshuijiang River Basin over the past 10 years. The results showed that the main ions in the river were Ca2+ and HCO3 -, with a cation order of Ca2+ (mean: 0.93 mmol/L) > Mg2+ (mean: 0.51 mmol/L) > Na+ (mean: 0.30 mmol/L) > K+ (mean: 0.06 mmol/L) and HCO3 - (mean: 2.00 mmol/L) > SO4 2- (mean: 0.49 mmol/L) > Cl- (mean: 0.15 mmol/L) > NO3 - (mean: 0.096 mmol/L) > F- (mean : 0.012 mmol/L). In the past 10 years, the concentration of major ions in the river water in the basin has increased significantly. The weathering input of rock (mainly upstream carbonate) was the main source of Mg2+, Ca2+, and HCO3 -, though sulfuric acid was also involved in this process. While K+ and Na+ were affected by the combination of human activity and the weathering input of silicate rock in the middle and lower reaches of the river, human activity was the main source of SO4 2-, NO3 -, and F- ions. Irrigation water quality and health risks were evaluated by calculating the sodium adsorption ratio (SAR), soluble sodium percentage (Na%), residual sodium carbonate (RSC), and hazard quotient (HQ). The findings indicated that the river water was generally safe for irrigation and drinking, and the health risks were gradually reduced over time. However, long-term monitoring of the river basin is still essential, especially for the risk of excessive F- in a few tributaries in the basin.

The mechanism of dolomitization in a stromatolite mound in the late Cambrian Chaomidian Formation, Shandong Province, China

Clarifying the mechanism of dolomitization is of pivotal importance and represents a burning issue among geologists. A comprehensive model to define the genesis of dolomitization in the Cambrian Chaomidian Formation carbonates is still lacking. In the highly focused study, the advanced integration of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), clumped isotope and carbon/oxygen isotope analyses was used to reveal complex interactions between the genesis and dolomitization of a stromatolite mound in the late Cambrian Chaomidian Formation of China. The results show that the dolomite content increases from bottom to top, along with a shift in lithology from limestone to dolostone. Additionally, as we moved from the base to the summit of the stromatolite mound, the Fe, Mn, and Na contents increase with increasing Mg levels, whereas the δ13C and δ18O values became more positive. Conversely, the levels of Sr and total rare earth elements (REEs) gradually decreased. The dolomite grains in the stromatolite mound are micritic and euhedral to subhedral, with foggy cores and bright edges and low cation ordering. The stromatolite limestone, dolostone, and underlying lime mudstone samples exhibit similar REE patterns: light REE enrichment, heavy REE loss, negative δEu anomalies, and weak negative δCe anomalies. The δ13C and δ18O values fall within the late Cambrian seawater range, suggesting that dolomitizing fluids originated mainly from concentrated seawater and migrated from top to bottom. The δ18O values indicate lower dolomite formation temperatures than calcite formation temperatures, supporting dolomitization during the penecontemporaneous diagenetic stage. Petrographic evidence reveals the presence of pyrite, indicating sulfate-reducing bacterial activity during diagenesis. XPS analysis revealed similar organic functional groups in both the stromatolite limestone and the dolostone, including C-(C = O)-O, C–C/C-(C–H), C-O and C-N. However, the dolostone spectrum exhibited a larger C-OH/C-O peak area, suggesting significant microbial organic matter involvement in dolomite formation. While a kinetic obstacle is recognized as a primary cause of dolomite formation, this study also suggested that microbial activity weakened this obstacle during diagenesis. Thus, microbial metabolism or cyanobacterial decomposition facilitates dolomite formation during the penecontemporaneous diagenetic stage.

Supplying active lithium to single-crystal Li(Ni0.90Co0.05Mn0.05)0.98Ta0.02O2 with Li2MnO3 coating served as cathode for Li-ion batteries

Ni-rich layered oxide with Ni molar content larger than 90% was regarded as an extremely promising candidate for cathode material applied in lithium-ion batteries owing to the significant discharging capacity and low cost. Nevertheless, rigorous cycling attenuation resulted from the crystal structure collapse and unstable particles interface deeply restrained the commercial application. In the work, LiNi0.90Co0.05Mn0.05O2 was modified by Ta5+ doping and Li2MnO3 covering, which was aimed to enhance the structure stability, defend the electrolyte attacking and promote Li+ migration during cycling. The material characterization demonstrated the cathodes after Ta5+ doping delivered the larger cell lattice parameters and higher cation ordering, which was helpful to improve the rate property and discharge capacity at low temperature. The Li2MnO3 layer was tightly adhered on the outside of LiNi0.90Co0.05Mn0.05O2, which could effectively relieve the electrolyte attacking and sustain the particle morphology integrity. As a result, 2wt.% Li2MnO3 coated Li(Ni0.90Co0.05Mn0.05)0.98Ta0.02O2 exhibited the outstanding discharge capacity of 150.2 mAh g−1 at 10.0 large current density and 140.6 mAh g−1 at -30 °C as well as the remarkable capacity retention of 93.1% after 300 cycles. Meanwhile, the pouch full batteries obtained by 2wt.% Li2MnO3 coated Li(Ni0.90Co0.05Mn0.05)0.98Ta0.02O2 also showed the more stable storage capability, cyclic property in comparison with bare LiNi0.90Co0.05Mn0.05O2.

Size polydisperse model ionic liquid under confinement: A molecular dynamics study

The performance of an electric double-layer capacitor is strongly influenced by the choice of electrolyte, and the use of ionic liquid (IL) mixtures as an electrolyte has shown great promise. In this study, a model IL made of a mixture of anions and size-polydisperse cations in equal numbers and confined between two electrodes is investigated by means of molecular dynamics simulations. In particular, using the extent of size-polydispersity (characterized by polydispersity index, δ) as a control parameter, we systematically explore its effect on the local structure, charge profile, ion size distribution in the vicinity of electrode surfaces, and differential capacitance. It is observed that the charge density profiles near cathode, i.e., region comprising both Stern and diffused layers, are significantly affected under the variation of δ in addition to the electrode charge density. Ion population, ordering of different-size cations, and its effective size in the vicinity of electrodes under neutral and applied potential conditions are also quantified. An interesting observation is that the effective cation size in the Stern layer decreases with increasing value of δ in the case of moderate to strong electrode surface charge density. This behaviour can be qualitatively understood from the interplay of enthalpic and entropic forces in the system. Finally, a non-monotomic dependence of capacitance on δ is observed with maximum value of capacitance at a rather small value of δ(≈3%) for the model system.

Thermally activated damage recovery in ion‐irradiated Gd2Ti2‐yZryO7 pyrochlore

AbstractIonizing events having a wide variety of radiation‐induced effects can radically affect the kinetics of defect production or structural transformation in the pyrochlore structured oxides (A2B2O7). Therefore, a thorough understanding of the kinetics associated with cation ordering and disordering is required for various technological applications. The structural responses of Gd2Ti2‐yZryO7 (y = 0.4, 1.2, 1.6) pyrochlore series irradiated by 120 MeV Au9+ ions were investigated using in situ synchrotron x‐ray diffraction (SR‐XRD), micro‐Raman spectroscopy, and scanning electron microscopy (SEM). Each pyrochlore composition irradiated at the highest fluence, where structural modifications occur, was subsequently isochronally annealed from room temperature to 1000°C. The SR‐XRD results indicate that Ti‐rich composition (y = 0.4) retains its pre‐irradiated pyrochlore structure (Fdm) at 1000°C. In contrast, Zr‐rich compositions exhibit recrystallization to an intermediate defect‐fluorite phase (Fmm) above 500°C, and the pre‐irradiated pyrochlore superstructure does not recover even on annealing at 1000°C. These results reveal that recrystallization temperature strongly depends on the accumulated radiation damage, generally described with the cationic radius ratio (rA/rB). Thus, investigation of the thermal annealing behavior of irradiated pyrochlores helps better understanding the general mechanisms of radiation damage and recovery of pyrochlores, which is important for their use in nuclear applications.

Influence of local cation order on the electronic structure and optical properties of cation-disordered semiconductor AgBiS2

Abstract Site disorder exists in some practical semiconductors and can significantly impact their intrinsic properties both beneficially and detrimentally. However, the uncertain local order and structure poses a challenge for both experimental and theoretical research. Especially, it hinders the investigation of the effects of the diverse local atomic environments resulting from the site disorder. In this study, we employ the special quasi-random structure method to perform first-principles research on the connection between local site disorder and electronic/optical properties, using the cation-disordered AgBiS2 (rock salt phase) as an example. We predict that cation-disordered AgBiS2 has a bandgap ranging from 0.6 to 0.8 eV without spin-orbit coupling and that spin-orbit coupling reduces this by approximately 0.3 eV. We observe the effects of local structural features in the disordered lattice, such as the one-dimensional chain-like aggregation of cations that results in the formation of doping energy bands near the band edges, the formation and broadening of band-tail states, and the disturbance in the local electrostatic potential, which significantly reduces the bandgap and stability. The influence of these ordered features on the optical properties is confined to alterations in the bandgap and does not markedly affect the joint density of states or optical absorption. Our study provides a research roadmap for exploring the electronic structure of site-disordered semiconductor materials, suggests that the ordered chain-like aggregation of cations is an effective way to regulate the bandgap of AgBiS2, and provides insight into how variations in local order associated with processing can affect properties.

Temperature and volumetric effects on structural and dielectric properties of hybrid perovskites

Three-dimensional organic-inorganic perovskites are rapidly evolving materials with diverse applications. This study focuses on their two representatives - acetamidinium manganese(II) formate (AceMn) and formamidinium manganese(II) formate (FMDMn) – subjected to varying temperature and pressure. We show that AceMn undergoes atypical pressure-induced structural transformations at room temperature, increasing the symmetry from ambient-pressure P21/n phase II to the high-pressure Pbca phase III. In turn, FMDMn in its C2/c phase II displays temperature- and pressure-induced ordering of cage cations that proceeds without changing the phase symmetry or energy barriers. The FMD+ cations do not order under constant volume across the pressure-temperature plane, despite similar pressure and temperature evolution of the unit-cell parameters. Temperature and pressure affect the cage cations differently, which is particularly pronounced in their relaxation dynamics seen by dielectric spectroscopy. Their motion require a rearrangement of the metal-formate framework, resulting in the energy and volumetric barriers defined by temperature-independent activation energy and activation volume parameters. As this process is phonon-assisted, the relaxation time is strongly temperature-dependent. Consequently, relaxation times do not scale with unit-cell volume nor H-bond lengths in formates, offering the possibility of tuning their electronic properties by external stimuli (like temperature or pressure) even without any structural changes.

Global Optimization of Cation Ordering in Perovskites by Recommendation-Based Basin-Hopping.

Cation ordering in multication perovskites is related to many important material properties and performances, but computational determination of the cation ordering remains a major challenge. Here, we propose a new computational approach by introducing a machine learning recommender system into the basin-hopping framework (RBH) for optimizing cation ordering. Taking the electrocatalyst Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF5582) as a showcase example, we found that the efficiency of RBH in identifying low-energy configurations outperforms the methods of cluster expansion and conventional basin-hopping. The RBH results revealed that the BSCF5582 catalyst tended to have a layered ordering of A-site cations and disordered B-site cations both in bulk and on the surfaces. Further, on the A-site-terminated surface, we found the segregation of large Ba atoms. Similarly, on the A-site- terminated surface of the recently developed Cs0.2Sr0.8Co0.4Fe0.6O3 (CSCF2846) catalyst, layered ordering at the A-site and surface enrichment of large Cs atoms were also found. The layered ordering was robust against thermal effects, as found from molecular dynamics simulations at 800 K. This work provides a new approach for thermodynamic global optimization of chemical ordering in multicomponent materials.

Photo‐Excited Switching and Enhancement of Dielectric Properties in Two‐Dimensional Double Perovskite Phase Transition Thin Films

Comprehensive SummaryOptical controlling of solid‐sate electric properties is emerging as a non‐contact and nondestructive avenue to optimize the physical properties of electronic and optoelectronic devices. In term of strong light‐material coupling, two‐dimensional (2D) double perovskites hold great prospects to create photo‐dielectric activities for high‐performance device applications. Here, we have achieved the photo‐excited switching and enhancement of dielectric properties in the orientational thin films of a 2D double perovskite, (C4H12N)4AgBiI8 (1, where C4H9NH3+ is isobutylammonium). It undergoes a structural phase transition at 384 K (Tc), triggered by the dynamic ordering of organic cations and tilting motion of isometallic perovskite sheets. Most notably, the orientational thin films of 1 are extremely sensitive to light illumination, of which the dielectric constants can be facilely photo‐switched between the low‐ and high‐states. During this photo‐switching process, the dielectric constants are enhanced with a magnitude up to ~350% under 405 nm, far beyond most of the inorganic phase transition counterparts. In addition, this photo‐excited switching and enhancement of dielectric response exhibits an operational stability with superior anti‐fatigue characteristics. Our work opens up a potential avenue for assembling high‐performance optoelectronic devices with the controllable physical properties.

Enhanced exchange bias in all-oxide heterostructures with cation-ordered ferrimagnetic double-perovskite

The realization and control of exchange bias (EB) are highly desirable for spintronic applications. All-oxide heterostructures comprised of ferromagnetic and antiferromagnetic/multiferroic oxides provide an ideal platform to enable the electric-field control of EB, promising for energy-efficient memory and logic devices. However, the low block temperature (TB) and small bias field (HEB) hinder further advances towards room-temperature applications. Here, we report an alternative approach to enhance the interface-induced EB by using ferrimagnetic double-perovskite with B-site cation ordering. In heterostructures comprised of double-perovskite Sr2FeReO6 (SFRO) and LaFeO3 (LFO), a high TB (about 250 K) and large HEB are observed, which is significantly larger than the counterparts with LFO and ferromagnetic oxides. Further analysis suggests that the cation-ordering and ferrimagnetic spin structure of the double-perovskite could contribute significantly to the enhanced exchanged bias when interfacing with G-type antiferromagnets. Our results open a new avenue for developing all-oxides heterostructures for future magnetic technologies.

Photoluminescence Tuning of Stable CaYGaO4: Bi/Eu via Compositional Modulation and Crystallographic Site Engineering for nUV wLEDs.

The olivine-based gallate CaYGaO4 (CYG) with unique cationic ordering, rich lattice sites, and self-photoluminescence (PL) is suitable for application as a host of phosphor. However, research in this area is still in its early stages, especially in high-quality full-spectrum white lighting. Herein, novel CYG: Bi3+/Eu3+ with a controllable PL property is designed based on energy transfer and superposition of emissions from blue self-PL, blue PL of Bi3+, and red-PL of Eu3+. Intriguingly, PL intensity and quantum efficiency could be enhanced via codoping Li+/Zn2+ separately/simultaneously because of their two intentional functions as both charge balancer and flux. Unlike self- and Eu3+ PL, Bi3+ PL is quite sensitive to the lattice environment owing to its exposed 6s2 electronic configuration and is tuned via codoping Sr2+ to regulate the nephelauxetic effect and crystal field splitting concurrently around Bi3+. Meanwhile, for further regulating the PL of Bi3+ and obtaining "warm" white light, La3+ is codoped into the phosphor via crystallographic site engineering to control the substitution trends of Bi3+ at distinct lattice sites. Finally, as a proof-of-concept, a full-spectrum phosphor-converted white-light-emitting diode device under nUV pumping with remarkable color rendering index (Ra), high luminous efficiency, and chemical/thermal stability is achieved by utilizing the individual CYG:Bi/Eu/Li/Zn/Sr/La phosphor via a remote "capping" packaging method.

Understanding the Role of Entropy in Promoting Electrocatalytic CO2 Reduction

A global push towards increased sustainability requires technologies that enable the long-term storage of renewable electricity and the sustainable synthesis of chemicals. The electrochemical reduction of CO2 to fuels and chemicals represents a promising avenue to meet these goals. Yet, despite extensive research, many fundamental aspects of the interfacial interactions that enable this reaction remain unclear. One simple question that has not been addressed to date is the mechanism through which the applied potential controls the rate of CO2 reduction. To provide insight, we measured CO2 reduction activation energies on Ag electrodes in the presence of different cations. Building on our earlier work (J. Am. Chem. Soc. 2016, 138, 25, 7820–7823), where some of us demonstrated the important role of structural modifications to imidazolium cations in controlling the rate of CO2 reduction reactions, we expected that these structural modifications impact the reaction rate through changes to the activation energy. However, our findings revealed a much more fascinating picture of the impact of imidazolium cations on CO2 reduction rates.By measuring the activation energy in the presence of imidazolium cations with different structural features, we find that introducing 1-ethly-3-methylimidazolium (EMIM) results in an apparent activation energy of zero. Under these conditions, the applied potential modifies the reaction rate solely through changes to the pre-exponential factor of the Arrhenius equation.Based on literature on homogeneous catalysis, we suggest that our finding indicates that the rate of CO2 reduction in the presence of EMIM is entirely controlled by the formation entropy of the CO2 reduction transition state, with the potential likely influencing the rate by modifying the degree of ordering of imidazolium cations at the electrode surface. We further show that proton abstraction from EMIM forms a neutral compound, resulting in the elimination of the rate enhancement. Our results provide important new insight into the mechanism through which the applied potential controls the rate of electrocatalytic reactions and we expect them to be of broad importance to a better understanding of the connection between interface structure and electrocatalytic rates.

Investigating the Synthesis Pathway of a Disordered Rocksalt Phase Via in Situ X-Ray Characterization

Recently, Li-rich disordered rocksalt (DRX) materials have gathered a lot of attention as prospective Li-ion battery cathode materials owing to their high electrochemical storage capacity and high specific energy. In contrast to the current commercialized layered Li-ion battery cathode materials (e.g. LiCoO2, LiNixMnyCo1-x-yO2), which contain toxic and expensive metals, DRX can accommodate a large variety of transition metals, such as Mn and Ti, which are cheap and earth abundant. These characteristics make them a cheaper and a more sustainable alternative to the current commonly used layered cathodes.Unlike the commercial Li-ion battery cathodes, where the transition metals and the Li are arranged in an ordered manner, DRX exhibits a highly disordered cation framework. Fluorine incorporation into DRX was extensively studied, where the fluorine anions are distributed disorderly at the anion sites. Previous studies have shown that the electrochemical performance of DRX cathodes can be enhanced via fluorination, as fluorine can effectively suppress the oxygen redox activity observed in many Li-rich cathodes. However, a large degree of fluorine incorporation into DRX was found to be difficult. As a result, it is important to study the mechanism in which fluorine is incorporated into the structure, and the role of LiF during synthesis of DRX.In addition to fluorination, the degree and type of short-range cation ordering (SRO) presenting in the materials were also found to have a significant impact on the electrochemical performance of DRX materials. The SRO present can be modified with synthesis techniques, where samples annealed at the synthesis temperature for a longer period exhibit a higher degree of SRO. This observation has demonstrated that the synthesis conditions and SRO are highly correlated. It is hence possible to control the SRO in DRX materials via varying synthesis conditions, thereby enhancing their electrochemical performance. Keeping this in mind, it is hence important to understand the mechanism by which DRX is formed.In this work, we have performed in situ synchrotron X-ray diffraction monitoring the phase progression during the solid-state synthesis of Li1.1Mn0.8Ti0.1O1.9F0.1 DRX oxyfluoride. We have observed several crystalline intermediate phases emerged before the formation of the DRX phase. Coupled with X-ray absorption spectroscopy, we are able to gain additional insights into the intermediate phases formed during the synthesis. This poster will describe the investigation of the synthesis pathway of Li1.1Mn0.8Ti0.1O1.9F0.1 DRX oxyfluoride using X-ray characterization techniques. The formation mechanism of this DRX phase will also be discussed.

Beyond Cation Disorder: Site Symmetry‐Tuned Optoelectronic Properties of the Ternary Nitride Photoabsorber ZrTaN3

AbstractTernary nitrides are rapidly emerging as promising compounds for optoelectronic and energy conversion applications, yet comparatively little of this vast composition space has been explored. Furthermore, the crystal structures of these compounds can exhibit a significant amount of disorder, the consequences of which are not yet well understood. Here, the deposition of bixbyite‐type ZrTaN3 thin films is demonstrated by reactive magnetron co‐sputtering and observed semiconducting character, with a strong optical absorption onset at 1.8 eV and significant photoactivity, with prospective application as functional photoanodes. It is found that Wyckoff‐site occupancy of cations is a critical factor in determining these beneficial optoelectronic properties. First‐principles calculations show that cation disorder leads to minor deviations in the total energy but modulates the bandgap by 0.5 eV, changing orbital hybridization of valence and conduction band states. In addition to demonstrating that ZrTaN3 is a promising visible light‐absorbing semiconductor and active photoanode material, the findings provide important insights regarding the role of cation ordering on the electronic structure of ternary semiconductors. In particular, it is shown that not only cation order, but also the cationic Wyckoff site occupancy has a substantial impact on key optoelectronic properties, which can guide future design and synthesis of advanced semiconductors.

Hydrochemical and Formation Mechanism Studies of Groundwater in Quaternary Aquifer in a Northern Plain of China: An Example of Beijing Plain

Beijing Plain is a very active part of Beijing city regarding the socio-economic and human activities of the region. Over the past four decades, Beijing’s economic development and the continuous drought for nearly 10 years in the 2000s have negatively impacted the groundwater quantity and quality. Therefore, it is necessary to investigate the present situation of groundwater chemistry in this region to develop a comprehensive database and orientation for future research on groundwater quality evaluation. Mathematical statistics, Piper’s trilinear diagram, Gibbs plots, the ion ratio method and PHREEQC software 3.7.3 were used to analyze the groundwater hydrogeochemical characteristics and formation mechanisms of the quaternary aquifers of the Beijing Plain area. Hydrogeochemical results indicated that the groundwater is slightly alkaline, with pH values ranging from 6.76 to 8.65 and an average value of 7.92. The order of major cations in groundwater was Ca2+ > Na+ > Mg2+ > K+ with average values of 66.54 mg/L, 50.58 mg/L, 23.78 mg/L, and 1.81 mg/L, respectively, while the order of major anions was HCO3− > SO42− > Cl− with average values of 284.89 mg/L, 52.1 mg/L and 35.5 mg/L, respectively. The groundwater chemical types are Mg-Ca-Cl-HCO3, Na-Ca-HCO3, Mg-Ca-HCO3 and Mg-Na-HCO3. Research on the main influencing factors and PHREEQC hydrogeochemical inverse simulations results along the four pathways selected confirmed that rock weathering with sulfate, silicate and carbonate rock mineral dissolution and Na+, Mg2+ and Ca2+ ion reaction exchange influenced groundwater hydrogeochemical characteristics of the quaternary aquifers of the Beijing Plain area. Understanding the formation mechanisms of hydrogeochemistry in quaternary plains provides guidance for future studies and, through suggestions and case studies, facilitates decision-making by policy-makers on the sustainable management of groundwater resources.

Hydrochemical Characteristics and Controlling Factors of the Mingyong River Water of the Meili Snow Mountains, China

The hydrochemical characteristics of rivers are affected by many natural factors, such as the nature of watershed bedrock, watershed environment, vegetation, and human activities. Examining the hydrochemistry of a river can provide insights into the baseline hydrological conditions, the geochemical environment, and the overall water quality of the river. In order to examine the hydrochemical characteristics and controlling factors of the water in the Mingyong River, a total of 154 water samples were gathered from the glacier meltwater, midstream, and downstream regions. Firstly, the findings revealed that the dominant cations are Ca2+ and Mg2+, while the dominant anions are HCO3− and SO42−. The mass concentration order of cations is Ca2+ > Mg2+ > Na+ > K+, and for anions, it is HCO3− > SO42− > NO3− > Cl−. The average concentration of TDS in the river water is 81.69 mg·L−1, with an average EC of 163.63 μs·cm−1 and an average pH of 8.99. Temporal variations in ion concentrations exhibit significant disparities between the glacier melting and accumulation periods. High ion concentration values are primarily observed during the glacier accumulation period, while values decrease during the glacier melting period due to increased precipitation. The river water in the study region is categorized as (HCO3− + SO42−)-(Ca2+ + Mg2+) type. Secondly, the Pearson correlation analysis indicates clear relationships between different parameters, indicating that the major ions were mostly influenced by materials from the Earth’s crust. The primary principal source of solutes in the water of the Mingyong River is rock weathering. The cations and anions present in the river water are derived from the breakdown of carbonate rocks and the dissolving of substances from silicate rocks. However, the influence of carbonate rocks is more significant compared to that of silicate rocks. Finally, the Mingyong River water is suitable for agricultural irrigation with minimal land salinization damage, making it appropriate for agricultural purposes but not suitable for people and animals to drink from directly.

Prediction of Novel Trigonal Chloride Superionic Conductors as Promising Solid Electrolytes for All-Solid-State Lithium Batteries.

Recently emerging lithium ternary chlorides have attracted increasing attention for solid-state electrolytes (SSEs) due to their favorable combination between ionic conductivity and electrochemical stability. However, a noticeable discrepancy in Li-ion conductivity persists between chloride SSEs and organic liquid electrolytes, underscoring the need for designing novel chloride SSEs with enhanced Li-ion conductivity. Herein, an intriguing trigonal structure (i.e., Li3SmCl6 with space group P3112) is identified using the global structure searching method in conjunction with first-principles calculations, and its potential for SSEs is systematically evaluated. Importantly, the structure of Li3SmCl6 exhibits a high ionic conductivity of 15.46 mS cm-1 at room temperature due to the 3D lithium percolation framework distinct from previous proposals, associated with the unique in-plane cation ordering and stacking sequences. Furthermore, it is unveiled that Li3SmCl6 possesses a wide electrochemical window of 0.73-4.30V vs Li+/Li and excellent chemical interface stability with high-voltage cathodes. Several other Li3MCl6 (M = Er, and In) materials with isomorphic structures to Li3SmCl6 are also found to be potential chloride SSEs, suggesting the broader applicability of this structure. This work reveals a new class of ternary chloride SSEs and sheds light on strategy for structure searching in the design of high-performance SSEs.

Enhanced cation ordering, electron-spin-phonon interactions and Fano resonance in half-metallic Sr2FeMoO6 thin films

We report the presence of electron-spin-phonon interactions in half-metallic ferromagnetic Sr2FeMoO6 (SFMO) double perovskite thin films using temperature-dependent Raman spectroscopy. A series of SFMO thin films have been prepared on LaAlO3 (001) single-crystal substrate using the Pulsed Laser Deposition technique. These depositions have been made in different gas-conditions such as in vacuum, and under nitrogen and oxygen gas pressures. At room temperature, Raman spectra manifest a Fano feature which indicates the presence of electron-phonon coupling in the films. The electron-phonon coupling strength further changes with a change in deposition conditions. Magnetization results show that the SFMO film grown in vacuum has the highest saturation magnetization which suggests better cation ordering as compared to the other films. For enhanced understanding, Raman spectra were recorded at varied temperatures and the data were analyzed by theoretical model fittings. A parameter quantifying temperature-dependent anharmonic nature of phonons has been derived using Balkanski model fits. This parameter shows a drastic deviation in the vicinity of Curie temperatures, manifesting a spin-phonon coupling in SFMO films. We further show that the spin-phonon coupling strengthens with improved Fe–Mo ordering. Any experimental observation of spin-phonon coupling has not been reported for SFMO systems till date. The magnetization data corroborate well with these observations made by Raman measurements. Our results of Raman spectroscopy, magnetization and resistivity collectively suggest that the SFMO films exhibit electron-spin-phonon interactions, which are influenced by the cation ordering. We also devised out the method of relating the anharmonic nature of Raman modes with the degree of Fe–Mo ordering and spin-phonon coupling in double-perovskite materials.