Tetrahedral Anions Research Articles

Where Fluoride Is Present, Hexafluorosilicate Might Be Encountered: Supramolecular Binding of the SiF6 2- Anion by Nanojars.

While the fact that HF etches glass is rather common chemical knowledge, the reaction of fluoride ions in an organic solvent with glassware under alkaline conditions has not yet been documented. It becomes apparent that, in general, whenever any fluorine-containing material is handled in silicon-based glassware, the possible presence of SiF6 2- should be considered regardless of the pH of the reaction medium. Subsequent to the initial, inadvertent synthesis by the reaction of CuF2 with laboratory glassware, hexafluorosilicate-entrapping supramolecular assemblies (nanojars) of the formula [SiF6⊂{cis-CuII(μ-OH)(μ-pz)} n ]2- (Cu n SiF 6 ; n = 28, 30, 32, 34) were rationally prepared by the reaction of Cu2+ with pyrazole (Hpz) in the presence of a base and SiF6 2- ions or by combining Cu n CO 3 with H2SiF6 or HF. This work demonstrates that nanojars are excellent anion-binding agents not only for trigonal planar/pyramidal or tetrahedral anions but also for larger, octahedral anions, which are bound exclusively by charge-assisted hydrogen bonds. The SiF6 2- anion guest is preferentially bound by a larger Cu32 host, whereas CO3 2- favors a smaller Cu27 nanojar. The Cu n SiF 6 mixture was characterized by electrospray ionization mass spectrometry as well as variable-temperature, paramagnetic 1H and 19F NMR spectroscopy in solution, complemented by single-crystal X-ray diffraction studies in the solid state, which reveal the unprecedented structure of a Cu8+14+10 nanojar (where Cu8, Cu10, and Cu14 are the component Cu x metallamacrocycles of the Cu32 nanojar).

Thermolysis of Cs9MO4 (M = In, Sc): Synthesis, Crystal Structure, Chemical Bonding, and Reactivity of the Subvalent Oxidometalates Cs7MO4 (M = In, Sc).

The cesium-poor alkali-metal suboxidometalates Cs7MO4 (M = In, Sc) were prepared from the respective cesium-rich suboxidometalates Cs9MO4 by thermolysis in a dynamic vacuum at temperatures below 150 °C. They crystallize in a new structure type, comprising isolated tetrahedral oxidometalate anions [MO4]5- immersed in a matrix of metallic cesium atoms. This structural separation into alternating ionic and metallic building units is typical for subvalent compounds. Cs7InO4 and Cs7ScO4 are isotypic and form mixed crystals Cs7(In1-xScx)O4 with statistic distribution of In and Sc atoms. All compounds were characterized by single crystal and powder X-ray diffraction. Calculations of the electronic structure with DFT methods corroborate the coexistence of anionic entities within a metallic matrix and give evidence of the subvalent nature of cesium atoms. Overall metallic behavior is a consequence of the equal volume fractions of metallic and ionic regions, allowing for percolation of the conduction electrons throughout the crystal volume. Differential thermoanalysis was employed to gain insight into the chemical conversion processes during the thermolysis reaction. The thermolytic decomposition of Cs9MO4 is a multistep process with, in some instances, reversible amorphization and recrystallization steps. Finally, the formation of ionic compounds is observed. The full decomposition of Cs9ScO4 yields the two new oxidoscandates Cs14Sc4O13 and Cs17Sc5O15 with tetrahedral [ScO4] units connected to chain fragments and the indium compound yields cesium oxidoindates with low-condensed [InO4] building units. The cesium-poor suboxidometalates Cs7MO4 themselves can serve as starting materials for the synthesis of further, new suboxidometalates, as they show a unique reactivity toward metals.

Hybrid metal halide family with color-time-dual-resolved phosphorescence for multiplexed information security applications

Luminescent materials with engineered optical properties play an important role in anti-counterfeiting and information security technology. However, conventional luminescent coding is limited by fluorescence color or intensity, and high-level multi-dimensional luminescent encryption technology remains a critically challenging goal in different scenarios. To improve the encoding capacity, we present an optical multiplexing concept by synchronously manipulating the emission color and decay lifetimes of room-temperature phosphorescence materials at molecular level. Herein, we devise a family of zero-dimensional (0D) hybrid metal halides by combining organic phosphonium cations and metal halide tetrahedral anions as independent luminescent centers, which display blue phosphorescence and green persistent afterglow with the highest quantum yields of 39.9 % and 57.3 %, respectively. Significantly, the luminescence lifetime can be fine-tuned in the range of 0.0968–0.5046 μs and 33.46–125.61 ms as temporary time coding through precisely controlling the heavy atomic effect and inter-molecular interactions. As a consequence, synchronous blue phosphorescence and green afterglow are integrated into one 0D halide platform with adjustable emission lifetime acting as color- and time-resolved dual RTP materials, which realize the multiple applications in high-level anti-counterfeiting and information storage. The color-lifetime-dual-resolved encoding ability greatly broadens the scope of luminescent halide materials for optical multiplexing applications.

Application, structure, salts and complexes of lidocaine: a review. Part V. structure of bis(lidocaine) tetrachloridocuprate(II)

The review focuses on lidocaine (2-(diethylamino)-N-(2,6-dimethylphenyl)acetamide): in the first part, its use in various branches of medicine, as well as the structure of lidocaine, its salts and molecular complexes was discussed; in the second part the use of lidocaine in the composition of deep-eutectic solvents (DES), DES-microemulsions and complexes of lidocaine with zinc, copper, cobalt, platinum and iron was considered; in the 3rd the structure of bis(lidocaine) tetrachlorido-zincate(II) was considered, in the 4th part the structure of bis(lidocaine) tetrachloridoferrate(III) chloride was discussed, this part reports on the synthesis and structure of bis(lidocaine) tetra-chloridocuprate(II), (LidH)2[CuCl4], which crystallizes in the monoclinic space group P21/c with a = 15.7831(2), b = 24.2992(2), c = 17.8748(2) Å, β = 104.874(1)°, V = 6625.58(13) Å3, Z = 8, and Dc = 1.355 Mg/m3. The coordination of the Cu2+ ions with chlorine atoms generates two differently distorted tetrahedral anions [CuCl4]2–, while four protonated cations LidH+ remain in an outer coordination sphere. Anions and cations are associated by hydrogen bonds of the N–H···Cl type to form the 2{(LidH)2[CuCl4]} dimer, in which the distance between two copper atoms is 8.95 Å (c/2). With the help of hydrogen bonds of the type N–H···O and N–H·Cl, each dimer is connected with four neighboring dimers, resulting in a three-dimensional structure in which dimers lie at an angle of 28.39° to the a crystallographic axis in the ab planes located at a distance of 10.67 Å from each other.

Synthesis, Structural characterization and complex impedance analysis of a novel organic-inorganic hybrid compound based on Mercury (II) chloride

The organic-inorganic hybrid compounds are promising materials due to their electro-optical and semiconducting properties. In this study, a single crystal of (C6H16N)2[HgCl4] has been synthesized and characterized using single-crystal X-ray diffraction at room temperature, SEM/EDS and complex impedance spectroscopy. The crystal structure is centrosymmetric with the monoclinic system (P21/c space group). It consists of isolated tetrahedral anions [HgCl4]2− and protonated amines (C6H16N) +. SEM/EDS analyses proved the composition of the title compound. The frequency-dependent electrical and dielectric properties were analyses using complex impedance spectroscopy in the frequency range of 10−1 Hz – 1 MHz. The Nyquist plots (-Z’’ vs Z’) was characterized by the appearance of a single semicircle arc, indicating a non-Debye type relaxation process in the (C6H16N)2[HgCl4] material. The AC conductivity followed Jonscher law, and the variation of frequency exponent s with temperature suggested that non-overlapping small polaron tunneling (NSPT) is the dominant electrical transport mechanism. So, this work will be very beneficial to the further development of the (C6H16N)2[HgCl4] compound and its potential electrical applications.

Precise Post‐Synthetic Modification of Heterometal‐Organic Capsules for Selectively Encapsulating Tetrahedral Anions

AbstractPost‐synthetic modification plays a crucial role in precisely adjusting the structure and functions of advanced materials. Herein, we report the self‐assembly of a tubular heterometallic Pd3Cu6L16 capsule that incorporates Pd(II) and CuL1 metalloligands. This capsule undergoes further modification with two tridentate anionic ligands (L2) to afford a bicapped Pd3Cu6L16L22 capsule with an Edshammer polyhedral structure. By employing transition metal ions, acid, and oxidation agents, the bicapped capsule can be converted into an uncapped one. This uncapped form can then revert back to the bicapped structure on the addition of Br− ions and a base. Interestingly, introducing Ag+ ions leads to the removal of one L2 ligand from the bicapped capsule, yielding a mono‐capped Pd3Cu6L16L2 structure. Furthermore, the size of the anions critically influences the precise control over the post‐synthetic modifications of the capsules. It was demonstrated that these capsules selectively encapsulate tetrahedral anions, offering a novel approach for the design of intelligent molecular delivery systems.

Precise Post-Synthetic Modification of Heterometal-Organic Capsules for Selectively Encapsulating Tetrahedral Anions.

Post-synthetic modification plays a crucial role in precisely adjusting the structure and functions of advanced materials. Herein, we report the self-assembly of a tubular heterometallic Pd3Cu6L16 capsule that incorporates Pd(II) and CuL1 metalloligands. This capsule undergoes further modification with two tridentate anionic ligands (L2) to afford a bicapped Pd3Cu6L16L22 capsule with an Edshammer polyhedral structure. By employing transition metal ions, acid, and oxidation agents, the bicapped capsule can be converted into an uncapped one. This uncapped form can then revert back to the bicapped structure on the addition of Br- ions and a base. Interestingly, introducing Ag+ ions leads to the removal of one L2 ligand from the bicapped capsule, yielding a mono-capped Pd3Cu6L16L2 structure. Furthermore, the size of the anions critically influences the precise control over the post-synthetic modifications of the capsules. It was demonstrated that these capsules selectively encapsulate tetrahedral anions, offering a novel approach for the design of intelligent molecular delivery systems.

The Birefringence Modulation in Short‐Wave Ultraviolet Sulfates with Functional π‐Conjugated Cations and Polymerized Heteroleptic Tetrahedral Anions

AbstractSulfates with a large bandgap are always promising optical candidates. However, due to insufficient birefringence, their applications are restricted. Here, in terms of this deficiency, two strategies are proposed to rationally modulate the optical anisotropy of sulfates by cations and anions, respectively. For the cation modulation, the [C(NH2)3]Al(SO4)2·6H2O crystal is investigated, which exhibits an unprecedented birefringence (0.098 @ 546 nm) compared with other deep‐ultraviolet transparent sulfates, resulting from the synergy of π‐conjugated [C(NH2)3]+ and non‐π‐conjugated [SO4]2− groups. For the anion modulation, a novel functional group, [S3O6]2−, with a large polarizability anisotropy, is designed. Thus, a new crystal, NaKS3O6, is obtained, which exhibits a large birefringence of 0.130 @ 546 nm with a short ultraviolet absorption cutoff edge of 215 nm. These results confirm the validity of the strategies. Therefore, the strategies play an important role in improving sulfate's birefringence and then promoting their potential applications in advanced optical systems.

Magnetic anisotropy and slow relaxation of magnetisation in double salts containing four- and six-coordinate cobalt(II) complex ions.

Four novel Co(II) coordination compounds 1-4 of the general formula [Co(Ln)2][Co(NCY)4]·mCH3CN (where Ln are tridentate ligands L1 = 2,6-bis(1-hexyl-1H-benzimidazol-2-yl)pyridine for 1 and 2; L2 = 2,6-bis(1-octyl-1H-benzimidazol-2-yl)pyridine for 3; L3 = 2,6-bis(1-dodecyl-1H-benzimidazol-2-yl)pyridine for 4, Y = O for 1, 3, and 4 and Y = S for 2; m = 0 for 1 and 3, m = 0.5 for 2 and m = 2 for 4) were prepared and characterised. The molecular structures of all four compounds consist of the hexacoordinate complex cation [Co(Ln)2]2+ and tetracoordinate complex anion [Co(NCY)4]2-, with distorted octahedral and tetrahedral symmetry of coordination polyhedra, respectively. The electronic structures of all compounds feature an orbitally non-degenerate ground state well-separated from the lowest excited state, which allows the analysis of the magnetic anisotropy by the spin Hamiltonian model. ZFS parameters, derived from both CASSCF-NEVPT2 calculations and magnetic data analysis, indicate that tetrahedral anions [Co(NCY)4]2- exhibit small axial parameters |D| spanning the range of 2.2 to 7.7 cm-1, while octahedral cations [Co(Ln)2]2+ display significantly larger |D| parameters in the range of 37 to 95 cm-1. For 1-3, the Fourier-transform infrared magnetic spectroscopy (FIRMS) revealed a reasonable transmission with a magnetic absorption around the expected value for the ZFS accompanied by features allowing to identify phonon frequencies and simulate spin-phonon couplings. Dynamic magnetic investigations unveiled the field-induced slow relaxation of magnetisation, with maximal relaxation times (τ) of 92(2) μs for 2 at 2 K and BDC = 0.3 T. The temperature evolution of τ was analysed using a combination of Orbach, direct and Raman relaxations (Ueff = 8(1) K (5.6 cm-1)) or Orbach, direct and spin-phonon induced relaxations (Ueff = 10.3(9) K (7.2 cm-1)). The rest of the complexes, namely 1, 3, and 4 show field-induced slow relaxation of magnetisation with τ smaller than 16 μs.

Phosphate selective binding and sensing by halogen bonding tripodal copper(II) metallo-receptors in aqueous media.

Combining the potency of non-covalent halogen bonding (XB) with metal ion coordination, the synthesis and characterisation of a series of hydrophilic XB tripodal Cu(II) metallo-receptors, strategically designed for tetrahedral anion guest binding and sensing in aqueous media is described. The reported metallo-hosts contain a tripodal C3-symmetric tris-iodotriazole XB donor anion recognition motif terminally functionalised with tri(ethylene glycol) and permethylated β-cyclodextrin functionalities to impart aqueous solubility. Optical UV-vis anion binding studies in combination with unprecedented quantitative EPR anion titration investigations reveal the XB Cu(II) metallo-receptors exhibit strong and selective phosphate recognition over a range of other monocharged anionic species in competitive aqueous solution containing 40% water, notably outperforming a hydrogen bonding (HB) Cu(II) metallo-receptor counterpart. Electrochemical studies demonstrate further the capability of the metallo-receptors to sense anions via significant cathodic perturbations of the respective Cu(II)/Cu(I) redox couple.

Halide-triggered assembly and selective bisulfate recognition in a quadruply interlocked coordination cage.

Interlocked coordination cages are a class of multi-cavity architectures with applications in selective anion recognition, adaptive sensing, and catalysis. Controlling the partitioning of their cavities through ligand design and appropriate anion templates is critical to their guest binding scope, yet remains a challenge. Here, we present a thermodynamically stable [Pd2L4](BF4)4 cage assembled from a bis-monodentate ligand featuring a non-coordinating bis-pyrazole methane backbone. As a result of its idealized dimensions, NMR, ESI-MS, and X-ray analyses reveal that halides can trigger the interpenetration of this cage into a [X@Pd4L8]7+ dimer (X = Cl- or Br-) where the halide template resides only in the central pocket. The anion-cation pattern of this interlocked host facilitates exceptional binding affinity for the bisulfate anion in its two outer pockets (up to 106 M-1 in MeCN), strongly outcompeting other tetrahedral anions of similar size.

Halogen Bonding Tripodal Metallo-Receptors for Phosphate Recognition and Sensing in Aqueous-Containing Organic Media.

The anion recognition and electrochemical anion-sensing properties of halogen-bonding (XB) tripodal zinc(II) receptors strategically designed and constructed for tetrahedral anion guest binding are described. The XB tris(iodotriazole)-containing hosts exhibit high affinities and selectivities for inorganic phosphate over other more basic, mono-charged oxoanions such as acetate and the halides in a competitive CD3 CN/D2 O (9 : 1 v/v) aqueous solvent mixture. 1 H NMR anion binding and electrochemical voltammetric anion sensing studies with redox-active ferrocene functionalised metallo-tripodal receptor analogues, reveal each of the XB tripods as superior anion complexants when compared to their tris(prototriazole)-containing, hydrogen bonding (HB) counterparts, not only exemplifying the halogen bond as a strong alternative interaction to the traditional hydrogen bond for molecular recognition but also providing rare evidence of the ability of XB receptors to preferentially bind the "harder" phosphate oxoanion over the "softer" and less hydrated halides in aqueous containing media.

Two different coordination polyhedra in the crystal structure of a novel Zn(II) hybrid complex: DFT investigation, biological activities and emission properties

This work centers around the search for sophisticated hybrid compounds with versatile applications. A new compound, denoted as (C6H8NO)3[ZnCl4][ZnCl3(H2O)] (1), was synthesized and thoroughly characterized. The structural features were determined through the use of various analytical techniques, including spectroscopy (FT-IR, Raman), thermo-gravimetric analysis, and optical studies encompassing ultraviolet-visible spectroscopy, nonlinear optical (NLO), and fluorescence measurements. The crystalline arrangement was explored through single crystal X-ray diffraction analysis, revealing a triclinic crystal system with the P1¯ space group. The molecular composition comprises three distinct mono-protonated p-aminophenol (C6H8NO)+ cations alongside two isolated tetrahedral anions ([ZnCl4]2− and [ZnCl3(H2O)]−). The stabilization of this hybrid compound accounts for a wide array of interactions, including hydrogen bonds and π–π (ring-ring) interactions, as deduced from comprehensive analyses. Theoretical investigations were conducted employing density functional theory (DFT) at the Cam-B3LYP/Lanl2dz level, accompanied by a detailed examination of the atoms in molecules (AIM) utilizing the BCP point. Furthermore, the nonlinear optical (NLO) properties were assessed, encompassing the evaluation of dipole moment, linear polarizability, and second hyperpolarizability. Notably, the compound exhibited pronounced solid-state fluorescence when excited at 350 nm, displaying intense emission within the blue spectrum. The correlated color temperature (CCT) value was measured at 7011 K, indicative of a "cool" white light emission. Basically, the synthesized compound exhibited antibacterial efficiency against several strains of human pathogenic bacteria in vitro and considerable enzyme inhibitory activity against pathogenic microorganisms. This research underscores the characteristics of (1), making it an appealing contender for a variety of applications.

The Role of Chemical Pressure in the Formation of the Structure and Barocaloric Properties of Complex Fluorides and Oxyfluorides

The role of chemical pressure as an effective tool in the processes of formation of initial and distorted (as a result of structural transformations) phases, thermodynamic properties, and direct and inverse barocaloric effects in some complex oxyfluorides and fluorides with octahedral, tetrahedral, and spherical anion and cation groups in the structure has been studied. It is found that, due to the small temperature hysteresis and high baric sensitivity of materials, the maximum values of absolute and integral barocaloric characteristics can be implemented at low pressures. Correspondingly, the temperature range of reversibility of thermodynamic cycles based on fluorides/oxyfluorides as solid-state coolants can be expanded.

Understanding the Crystal Chemistry of Phosphate Cathode Materials

Thermal batteries are primary reserve batteries that can achieve high power output in a short period of time by melting an insulating salt electrolyte with a pyrotechnic heat source and converting it into a highly conductive eutectic salt electrolyte. The thermal battery exhibits no self-discharge before activation, and the initial capacity of the thermal battery is maintained after long-term storage. Thermal batteries are an attractive option for emergency power supplies in aircraft, ejector seats, space landings and helicopters due to their outstanding robustness, high reliability, and long-term storage properties.FeS2 or CoS2 are the most common cathode materials for thermal batteries.1 However, their high cost and relatively low discharge voltage makes it desirable to find new materials that have higher voltage discharges, higher specific capacities, low cost and that are environmentally friendly. Polyanion cathode materials have attracted much attention in the field of both Li-ion and Na-ion batteries,2–4 as they can be regarded as low-cost materials and environmentally friendly. However, to the best of our knowledge, there have been no studies on polyanion cathode materials for thermal batteries. These materials are formed by tetrahedral units (XO4)n- (X = P, S, Si or B) bonded to MO6 polyhedra (M = transition metal). The tetrahedral anion presents a very strong covalent bond between X-O, giving rise to higher voltages versus Li+/Li or Na+/Na via the inductive effect and their very stable framework and open structure facilitates ion diffusion. Thus, polyanion materials present high structural stability and enable the tuning of the operating potential, making them an excellent choice for developing new cathode materials for thermal batteries. Here we report some of our latest work on the synthesis, structure and electrochemistry of polyanionic cathode materials for thermal batteries. 1 R. Li, W. Guo and Y. Qian, Front. Chem., 2022, in press, doi: 10.3389/fchem.2022.832972 2 Z. Gong and Y. Yang, Energy Environ. Sci., 2011, 4, 3223–3242. 3 C. Masquelier and L. Croguennec, Chem. Rev., 2013, 113, 6552–6591. 4 Q. Ni, Y. Bai, F. Wu and C. Wu, Adv. Sci., 2017, 4, 1600275.

K2BaSi4: Zintl Concept in Position Space

AbstractThe Zintl phase K2BaSi4 has been synthesized from the mixture of precursors KSi and BaSi2. The crystal structure of K2BaSi4 was elucidated from X‐ray powder diffraction data: Pearson symbol oP28, space group Pbcm, a=9.4950(1), b=9.2392(1), c=9.9025(1) Å. The main building block of the crystal structure are tetrahedral anions Si44–. Analysis of chemical bonding for K2BaSi4 and its chemical analogs – molecular H4Si4 and solid state K4Si4 employing the electron localizability approach reveals the basic agreement with the Zintl model in terms of number of basins for Si−Si bonds and lone pairs at Si atoms, as well as the charge transfer direction. The populations of the bond and ‘lone‐pair’ basins agree with the Zintl count for molecular species and deviate strongly for the solids, in particular, while the ‘lone‐pair’ basins are over‐populated, the bond basins are essentially under‐populated. The topology of the calculated electron density and electron‐localizability indicator is very sensitive toward the interatomic distances and angles in the Si44− anion.

Crystal Structure, Spectroscopic Studies and Supramolecular Chemistry, DFT Based Electronic and Optical Properties of Salts of Methylene Blue with Tetrahedral Anions

AbstractThe Fe(III), Ni(II) and Zn(II) salts were treated with MB+ to obtain metal complexes MB[FeCl4], (MB)2[NiCl4], MB(ClO4) and to explore the coordination behavior of the organic cation. Crystals were grown by soft grinding and solution techniques. The resultant compounds were fully characterized by UV‐visible spectroscopy, TGA, single crystal and powder XRD. UV‐Visible, Frontier molecular orbital, Density of states, Molecular electrostatic potentials, and band gap were estimated theoretically by DFT. The purity and crystallinity of material was measured with the help of powder X‐ray diffraction analysis while their thermal stability was measured with the help of thermogravimetric analysis. DFT study revealed that the chlorinated metal center helps to stabilize the HOMO and LUMO values which are ultimately responsible for the lower energy gap. Complex (MB)2[NiCl4] has the lowest bandgap 0.48 eV which is due to the presence of one extra MB+ and also due to the electron‐rich nature of Ni(II). The crystal structure of all compounds is stabilized by strong electrostatic, hydrogen bonding, π‐π‐stacking and other short‐interactions. Molecular electrostatic potentials ESP surface shows that chlorinated metal centers are electron rich in nature and more electron density are found in center. The supramolecular chemistry of the resultant solids is discussed in detail.

Second‐harmonic generation and structural rearrangements in multicomponent antimonite glasses by electrothermal poling

AbstractElectrothermal poling is shown here to effectively induce second‐order nonlinear effects in heavy‐metal oxide antimonite glasses. In M2O–PbO–WO3–Sb2O3 (M = Li, Na, K) glasses, the poling‐induced second‐harmonic generation intensity is five times larger than in silica (Infrasil) for M = Na, twice as large as in silica for M = Li, and smaller than in silica for M = K. X‐ray photoelectron spectroscopy suggests that antimony ions exist predominantly in the trivalent oxidation state in the studied glass samples. Raman and infrared spectroscopy confirm that the glass network is comprised of SbO3, WO4, WO6, and PbO4 units—with some SiO4 moieties due to leaching from the silica crucible. The WO4 units appear to exist in two distinct sites, as evidenced by comparison of the vibrational spectra of alkali–tungsten–antimonite glasses with those of previously reported crystalline tungstate phases. The alkali type influences the equilibrium between tetrahedral tungstate anions, [WO4]2−, and the isomeric partially polymerized octahedral tungstate units, [WØ4O2]2− (Ø denotes a bridging oxygen). Raman spectroscopy line scans were used to track near‐surface structural changes on the anode side of poled glasses. They reveal that the tungstate equilibrium is also affected by poling. At the anode side, the population of partially polymerized [WØ4O2]2− species increases at the expense of anionic [WO4]2− species. This yields a net increase in the average bond length of the network forming constituents, which is commensurate with poling‐induced structural changes observed in other systems experimentally and computationally.

Evaluation of Surface Tension of CaO–SiO2–Al2O3‐Based Mold Flux Containing Ce2O3

The calculation model based on the surface tension of CaO–SiO2–Al2O3‐based mold flux containing Ce2O3 is studied using the modified Butler equation, and the surface tension of mold flux is measured by the sessile drop method. The experimental results show that the calculated surface tension based on the model agrees well with the experimental values, and the absolute value of the error is less than 3.23%. With the content of Ce2O3 in the mold flux increasing from 0% to 20%, the surface tension of the mold flux increases from 0.380 to 0.405 N m−1. The O2− dissociated from Ce2O3 makes the radius of the silicon–oxygen tetrahedral anion decrease, and the ion‐to‐ion interaction force in the melt increase. Therefore, the surface tension of the melt increases with the increase of Ce2O3 content in the mold flux. However, the amount of dissociated O2− is limited, so the effect of Ce2O3 on the surface tension of the mold flux is limited.

First-principles assessment of chemical lithiation of sulfide solid electrolytes and its impact on their transport, electronic and mechanical properties

Sulfide-based solid electrolytes (SEs) have received considerable attention, but their practical application is hindered by the lack of chemical stability. When in contact with Li metal, sulfide SEs may undergo decomposition induced by lithiation, which could be largely responsible for the high interfacial impedance observed between them. While the underlying mechanism is still uncertain, this first-principles study examines the structural and compositional evolution of sulfide materials, Li3PS4 and Li10GeP2S12, associated with chemical lithiation and its impact on their transport, electronic and mechanical properties. Our calculations demonstrate that the lithiation reaction is thermodynamically favorable until reaching full lithiation in which PS43− and GeS44− tetrahedral anions are completely decomposed to S2−, P3- and Ge4− atomic ions. This process is also found to involve the transition formation of small P(Ge) clusters and more importantly an increase in the relative density which may cause void formation and thus structural failure near the Li metal/SE interface. Moreover, our analyses highlight that, even when fully lithiated, the sulfide materials could retain the high Li-ion conductivity as well as the ability to block electron transport. This suggests that the chemical decomposition of sulfide SEs would not be the only factor that is responsible for the increase of interfacial impedance during electrochemical cycling.