Crystal Stability Research Articles

Electronic and optical properties of a Ta2NiSe5 monolayer: A first-principles study

The crystal structure, stability, electronic, and optical properties of the Ta2NiSe5 monolayer have been investigated using first-principles calculations in combination with the Bethe–Salpeter equation. The results show that it is feasible to directly exfoliate a Ta2NiSe5 monolayer from the low-temperature monoclinic phase. The monolayer is stable and behaves as a normal narrow-gap semiconductor with neither spontaneous excitons nor non-trivial topology. Despite the quasi-particle and optical gaps of only 266 and 200 meV, respectively, its optically active exciton has a binding energy up to 66 meV and can exist at room temperature. This makes it valuable for applications in infrared photodetection, especially its inherent in-plane anisotropy adds to its value in polarization sensing. It is also found that the inclusion of spin–orbit coupling is theoretically necessary to properly elucidate the optical and excitonic properties of a monolayer.

Crystal Structures of Sulfobetaine-8 Solvates: Bend Hydrophobic Chains and Doubly Charge-Assisted Hydrogen Bonds N+CH⋯−O3S

Three novel solvatomorphs (C13H29NO3S•CH3OH, 1; C13H29NO3S•0.113(H2O), 2; C13H29NO3S•0.038(H2O), 3) of zwitterionic sulfobetaine-8 were obtained and their structures were determined using single-crystal X-Ray diffraction. In all cases dimethyl–amino substituted hydrophobic chains -(CH2)3-N+Me2-(CH2)7-Me exhibit kinks at nitrogen atoms resulted from strong intra- and intermolecular CH⋯O hydrogen bonds between negatively charged sulfonic anion -O3S- and positively charged tetraalkylammonium fragments. Periodic (solid state) DFT calculations for structure 1 showed that the energy of the intermolecular hydrogen bonds CH…O is very high, at about 17 kJ/mol. In hydrates 2 and 3, water molecules play the structure-forming role since they interconnect hydrophobic layers by HOH…-O3S hydrogen bonds. The location of only partially occupied water molecules in the interlayer space leads to low stability of both crystals 2 and 3 in open air.

Comparative Study on the Electrocatalytic Performance of ABO3-Based Hexagonal Perovskite Oxides with Different [AO3] Layers.

To systematically investigate the influence of the number of [AO3] layers in the unit cell of hexagonal perovskite oxide on the oxygen evolution reaction performance, we successfully synthesized the three new hexagonal perovskite oxides 2H-BaCo0.9Ru0.1O3-δ, 6H-BaCo0.9Ru0.1O3-δ, and 10H-BaCo0.9Ru0.1O3-δ with the same element composition but different [BaO3] layers via the sol-gel method. Here, 2H, 6H, and 10H refer to the number of [BaO3] layers contained in the unit cell of the BaCo0.9Ru0.1O3-δ system. Experimentally, 10H-BaCo0.9Ru0.1O3-δ, featuring ten layers of [BaO3], exhibits optimal electrochemical activity among the three oxide catalysts, and in situ Raman results under various bias voltages confirm its ability to maintain a high surface crystal structural stability. Notably, as the number of [BaO3] layers increases, the effective magnetic moments and the valence state of surface Co ions in these three catalysts also increase, with the spin configuration of the surface Co ions being in a high-spin state. More importantly, DFT calculations provide the evolution rules of the p-band center (εp) with the number of [BaO3] layers, predicting the electrochemical performance of the BaCo0.9Ru0.1O3-δ system with different [BaO3] layers. Our experimental results offer a distinctive perspective for the future design, synthesis, and application of hexagonal perovskite oxides in electrocatalysis.

Anisotropy of the zigzag order in the Kitaev honeycomb magnet α−RuBr3

Kitaev materials often order magnetically at low temperatures due to the presence of non-Kitaev interactions. Torque magnetometry is a very sensitive technique for probing the magnetic anisotropy, which is critical in understanding the magnetic ground state. In this paper, we report detailed single-crystal torque measurements in the proposed Kitaev candidate honeycomb magnet α−RuBr3, which displays zigzag order below 34 K. Based on angular-dependent torque studies in magnetic fields up to 16 T rotated in the plane normal to the honeycomb layers, we find an easy-plane anisotropy with a temperature dependence of the torque amplitude following closely the behavior of the powder magnetic susceptibility. The torque for the field rotated in the honeycomb plane has a clear sixfold periodicity with a sawtooth shape, reflecting the threefold symmetry of the crystal structure and stabilization of different zigzag domains depending on the field orientation, with a torque amplitude that follows an order parameter form inside the zigzag phase. By comparing experimental data with theoretical calculations we highlight the importance of relevant anisotropic interactions and the role of the competition between different zigzag domains in this candidate Kitaev magnet. Published by the American Physical Society 2024

Influence of cobalt specialization state on color mechanism and ‘color dispersion’ behavior of blue-and-white porcelain

Ancient blue-and-white porcelains exhibit wide color variations and ‘color dispersion’ due to the use of different cobalt-based blue pigment in different periods. Nowadays, it is difficult to date back due to cobalt ore raw material exhaustion. To clarifying the wide color variations and ‘color dispersion’, Field emission scanning electron microscopy (FE-SEM), X-ray absorption fine structure (XAFS), Optical Microscope (OM), etc, were used to study the color mechanism and ‘color dispersion’ behavior of blue-and-white porcelain by comparing cobalt speciation state and crystal structure stability. The blue tones of blue-and-white porcelain are mainly due to Co2 + ions located in the tetrahedron structure in the glaze, and thus the ‘color dispersion’ distance is large. when Co2+ is located in the tetrahedral structure of the spinel crystal, the blue-and-white porcelain appears dark blue and thus the ‘color dispersion’ distance is small.

Role of van der Waals, Electrostatic, and Hydrogen-Bond Interactions for the Relative Stability of Cellulose Iβ and II Crystals.

Naturally occurring cellulose Iβ with its characteristic parallel orientation of cellulose chains is less stable than cellulose II, in which neighboring pairs of chains are oriented antiparallel to each other. While the distinct hydrogen-bond patterns of these two cellulose crystal forms are well established, the energetic role of the hydrogen bonds for crystal stability, in comparison to the van der Waals (vdW) and overall electrostatic interactions in the crystals, is a matter of current debate. In this article, we investigate the relative stability of celluloses Iβ and II in energy minimizations with classical force fields. We find that the larger stability of cellulose II results from clearly stronger electrostatic interchain energies that are only partially compensated for by stronger vdW interchain energies in cellulose Iβ. In addition, we show that a multipole description of hydrogen bonds that includes the COH groups of donor and acceptor oxygen atoms leads to consistent interchain hydrogen-bond energies that account for roughly 70% and 75% of the interchain electrostatics in celluloses Iβ and II, respectively.

Characterization of a New Hybrid Compound (C3H8N6)2ZnCl4·2Cl: X-ray Structure, Hirshfeld Surface, Vibrational, Thermal Stability, Dielectric Relaxation, and Electrical Conductivity.

A novel organic-inorganic material (C3H8N6)2ZnCl4·2Cl was synthesized via a slow evaporation approach and subjected to extensive characterization. Techniques involving X-ray diffraction, SEM/EDX, Hirshfeld surface examination, IR/Raman spectroscopy, thermal behavior (TG/DTG/SDTA and DSC), and electric and dielectric studies were applied. Examination of the crystal structure reveals that the synthesized material adopts a monoclinic system, particularly belonging to the P21/c space group with unit cell parameters a = 11.7274(3) Å, b = 6.2155(2) Å, c = 25.7877(8) Å, β = 94.27(1)°, V = 1874.50(4) Å3, and Z = 4. Purity confirmation was established via powder X-ray diffraction analysis. Composition verification was conducted using semiquantitative EDXS analysis. The asymmetric unit comprises isolated tetrachlorozincate [ZnCl4]2- anions, two (C3H8N6)2+ organic cations, and two free chlorine atoms, forming a 0D anionic network. N-H···Cl and N-H···N hydrogen bonding combined to form a 2D hydrogen-bonded network, maintaining crystal stability. Hirshfeld surface analysis elucidated intermolecular interactions, supported by 2D fingerprint plots. IR and Raman spectra analysis corroborated compound characteristics at room temperature. Thermal analysis revealed two phase transitions at 343 and 358 K, consistent with dielectric studies. Impedance spectroscopy highlighted the compound's electrical properties, confirming thermal transitions. Conductivity studies exhibited an Arrhenius behavior. Frequency-dependent dielectric constant variations and modulus studies underscored grain and grain boundary effects, confirming the effective protonic conduction in the material.

Enhancing Durability of Organic–Inorganic Hybrid Perovskite Solar Cells in High‐Temperature Environments: Exploring Thermal Stability, Molecular Structures, and AI Applications

AbstractThe commercialization of perovskite solar cells (PSCs), as an emerging industry, still faces competition from other renewable energy technologies in the market. It is essential to ensure that PSCs are durable and stable in high‐temperature environments in order to meet the varied market demands of hot regions or seasons. The influence of high temperatures on the PSCs is complex, encompassing factors such as lattice strain, crystal phase changes, the creation of defects, and ion movement. Furthermore, it intensifies lattice vibrations and phonon scattering, which in turn impacts the migration rate of charge carriers. This review focuses on the durability of organic–inorganic hybrid PSCs under high temperatures. It begins by analyzing the impact of external temperature variations on the internal energy dynamics of PSCs. Subsequently, it outlines the various mechanisms provided by different functional molecules, applied to interface stabilization, grain boundary passivation, crystal growth control, electrode protection, and the development of new hole transport layers, to enhance the thermal stability of PSCs. Additionally, machine learning (ML) is discussed for predicting crystal structure stability, PSCs operational stability, and material screening, with a focus on the potential of deep learning and explainable artifical intelligence (AI) techniques in the commercialization of PSCs.

Na Ions Doped Fe2VO4 Cathode for High Performance Aqueous Zinc-ion Batteries.

Aqueous zinc ion batteries are thought to be a new generation of secondary batteries that will replace lithium-ion batteries due to their great safety and inexpensive cost. In the cathode materials of aqueous zinc ion batteries with long life and high capacity, abundant active sites and crystal structure stability play an important role. In the present work, the strategy of Na+ intercalation of Fe2VO4 (FVO) is proposed, aiming at the insertion of Na+, which not only enriches the active sites, but also sodium and iron ions act as guest species with the negatively charged VOx lattice to provide strong electrostatic attraction to stabilize the lamellar structure. In terms of electrochemical performance, the discharge specific capacity is 370 mAh g-1 at a current density of 0.1 A g-1, and when the current density is arising 5 A g-1, the specific capacity also reaches 200 mAh g-1 after cycling 2000 with a capacity retention of 99 %, which is better than the electrochemical performance of Fe2VO4 (FVO) alone at 50 mAh g-1. The superior electrochemical performance proves that FVO-Na is an ideal cathode material for zinc ion batteries.

Laser-Controlled Information Releasing and Hiding Based on Perovskite Phosphors.

Laser-active interference with high confidentiality and convenience opens up a cutting-edge path for releasing and hiding key targets; however, its development still faces enormous challenges owing to the difficulty of concealing objects. Herein, a novel conceptual design for laser-controlled information release and hiding (LIRH) is proposed and successfully realized. Cs2NaInCl6:Er3+, Yb3+ (CNIC:Er, Yb) perovskite microcrystal is adopted as a carrier for LIRH implementation, exhibiting excellent up-conversion (UC) emission under NIR (980 and 1530 nm) irradiation due to its ultralow phonon energy. The fluorescence intensity crossover and outstanding photon output capacity are revealed in comparison with Er3+/Yb3+ codoped and Er3+ single-doped CNIC phosphors under different laser sources, and the obvious difference in quantum yields (QY) under 980 and 1530 nm excitation provides theoretical possibility for LIRH. More importantly, the obtained LIRH features high stability at temperatures up to 413 K, showing good adaptability in various potential scenarios. Moreover, CNIC:Er, Yb is further combined with polyacrylonitrile (PAN) polymer to form fluorescent fibers with exceptional crystal stability and composite flexibility, thus making the LIRH code a reality based on perovskite composite phosphors. The laser-active invisibility offers an innovative idea for LIRH, further extending the application of LIRH in the field of information encryption, which has promising prospects in information safety, advanced anticounterfeiting, and smart responsive materials.

Solvatomorphs of the Dapsone Structurally Related Molecule 3,3′-Diaminodiphenyl Sulfone with Class 2 Residual Solvents: Insights into Their Crystal Structures, Stability, and Transformations

Solvatomorphs of the Dapsone Structurally Related Molecule 3,3′-Diaminodiphenyl Sulfone with Class 2 Residual Solvents: Insights into Their Crystal Structures, Stability, and Transformations

Synthesis and crystal structure of a novel metal cyanide halide complex (NH4)6Fe(CN)6Cl2·0.4H2O

Hexacyanidometallates possess unique physical properties, which has been extensively studied. However, there are still a number of its derivatives that may be considered which remains unknown, such as metal cyanide halide hexacyanidometallates, especially those of transition-metal elements, but preparing such complex is hampered by the preference of the formation of compounds without halogens. Here, we report synthesis of a novel transition metal cyanide halide hexacyanidometallates derivate (NH4)6Fe(CN)6Cl2·0.4H2O through reactant ratio control. The crystal structure was studied via single-crystal X-ray diffraction, supported by elemental analysis and IR spectra. The crystal structure of (NH4)6Fe(CN)6Cl2·0.4H2O crystallizes in space group R3¯ with rhombohedral stacking behavior. Moreover, the crystal structure of (NH4)6Fe(CN)6Cl2·0.4H2O features rich hydrogen bonds, contributing to the crystal stability.

Study of the effect of SMAW welding speed on the microstructure and crystal stability of X70 steel using X-ray diffraction

This study investigates the impact of manual electric arc welding (SMAW) speed on the microstructure of X70 steel. Welding was performed at two distinct speeds: S1 = 20 mm/min and S2 = 35 mm/min, at the COSIDER BISKRA workshop in Algeria. X-ray diffraction (XRD) analysis was conducted on the welded zones to examine crystal orientation, size, dislocation density, and structural stability across different welding areas, including the base metal (MB), heat-affected zones (HAZ1 and HAZ2), and weld zones (WZ1 and WZ2). The XRD results revealed that key crystal peaks, such as {110} and {200}, retained their positions at both welding speeds, though variations in {110} peak intensity were noted. The lower welding speed (S1) resulted in a higher heat input, which enhanced crystal stability, increased crystal size, and reduced dislocation density. On the other hand, the higher speed (S2) produced lower heat input, leading to smaller crystal sizes, increased residual stresses, and a greater number of defects due to rapid cooling. These findings underscore the critical influence of welding speed on heat input, cooling rates, and their consequent effects on microstructure. The study highlights the importance of optimizing welding parameters to balance microstructural integrity, mechanical performance, and production efficiency.

Comprehensive evaluation of mechanical properties, optoelectronic features, photovoltaic performance, and crystal stability of Ba3MX3 (M = As, Sb; X = Cl, Br, I)

Herein, the first-principles computations are utilized to study the optoelectronic properties, photovoltaic performance, crystal stability, and mechanical features of Ba3MX3 (M = As, Sb; X = Cl, Br, I). Through comprehensive structural stability evaluation, all compounds are determined to be stable. The results indicate that Ba3MX3 (M = As, Sb; X = Cl, Br) is brittle while both Ba3AsI3 and Ba3SbI3 are ductile. The HSE06-based electronic structure calculations show that the direct-gap nature is revealed for six compounds, and the energy band gaps are within the range of 1.35–1.65 eV. The fundamental band gap can be modulated by virtue of X-anion substitution. The low carrier effective masses are disclosed for these compounds. Their optical features exhibit that high solar absorption and weak reflectance and energy loss are observed. Ultimately, an ultra-high theoretical conversion efficiency of 31.9 % is implemented for Ba3MI3 (M = As, Sb). Besides, the remaining four compounds also have high conversion efficiencies within 29–30 %. From the suitability for practical applications, both Ba3AsI3 and Ba3SbI3 are chosen as the best candidates for the absorber layers of effective single-junction solar cells. Our findings unveil the suitability of these inorganic materials for optoelectronic applications.

Empirical, computational studies and non-covalent interactions analysis of a novel salt with cadmium transition metal precursor

In this research paper, (C3H5N2)6[CdCl4][CdCl6] was successfully synthesized using a slow evaporation process. The structure was confirmed through single-crystal X-ray crystallography, FT-IR, and thermal analysis. The material was found to crystallize in the tetragonal system (space group I41/a) and the following parameters a = b = 12.0872 (8) Å; c = 24.6985 (16) Å, the crystal packing shows parallel layers of cations and stacks of discrete anions positioned at y = 1/4 and 3/4. The junction between the monoprotonated imidazolium cations and the anions, along with the crystal structure stability, relies on Cl···H−N, and Cl···H−C hydrogen bonds. Computational investigations, conducted using the B3LYP method with 6–311++G(d,p) and LANL2DZ mixed basis set, demonstrated close alignment between the computed and the experimental data, providing insights into the material's geometrical and vibrational properties. The non-covalent interactions were studied through Atoms-In-Molecule (AIM) and Reduced Density Gradient (RDG) analysis and quantitatively using the Hirshfeld surfaces associated with 2D fingerprint plots. Furthermore, thermal stability was assessed through Thermogravimetric and Differential Scanning Calorimetry (TG–DSC) analysis.

Prediction of crystal structure, phase group, and stability of 2D materials through data science coupled with DFT

Two-dimensional materials offer unique mechanical strength, electrical conductivity, and tunable electronic properties, driving advancements in electronics, energy storage, and catalysis. The crystal structure of the materials is fundamental to several properties. In this study, we employ solely the elemental features to construct a random forest classification model achieving an 82.56 % accuracy in predicting the crystal structure of the compounds. Additionally, one vs rest binary classifiers are developed for each crystal structure within our 2D materials dataset, with accuracies ranging from 86 % to 99 %, enhancing their practical utility. Features based on stoichiometric norms have been found to play a major role in the prediction because of the fact that certain crystal structures are associated with more balanced compositions, leading to lower norm values, while others with imbalances have higher norm values. It has also been observed that material compositions with an overall higher amount of p valence electrons tend to show monoclinic, orthorhombic and triclinic crystal structures. Moreover, in compounds with a lower total electronegativity of the constituent elements, the occurrence of trigonal and tetragonal systems has been found to be more probable. In a similar fashion, hexagonal crystal systems have been more often found in compounds where the sum of Van Der Waals radius of the constituent atoms is lower. To validate our model, Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method, and Density Functional Theory (DFT) are utilized to predict the crystal structure, phase group, and stability of a 2D material.

Design, synthesis, structural, in silico, and in vitro exploration of structurally modified hydrazones of piperidin-4-one with acetyl & ester moieties

The accessibility and bioavailability of medicinally important molecules like piperidones can be improvised by specific structural modifications and such modifications can be effected by acetylation & esterification of core moiety, as it changes physicochemical properties. Synthesis of hydrazinecarboxylate derivatives of 1-(2-chloroacetyl)-3-methyl-2,6-diphenylpiperidin-4-ones (3a-i) which are structural hybrids of hydrazone of piperidone with acetyl and carboxylate templates is being reported in this paper. The synthesized compounds were structurally characterized by IR, 1H & 13C NMR, mass (3a-d, 3f) spectral techniques, and single crystal X-ray diffraction study (3b and 3d). For compound 3b, 2D NMR (HSQC & HMBC) was recorded for unambiguous assignments of chemical shifts. In addition to the SC-XRD for compounds 3b and 3d, the DFT study revealed the distorted boat conformation of the piperidone ring having E – configuration about the hydrazone moiety in both molecules. Hirshfeld surface analysis on 3b and 3d, exposed the H…H interaction in both the molecules supports their crystal stability to the maximum extent (≥ 53 %) while other interactions viz., O…H, Cl…H, C…H also contribute to the crystal stabilization. In silico bio-study for (3a-i) was done by AutoDock4 with human estrogen receptor (3ERT) protein and found the docking scores ranging from − 7.18 to − 8.64 kcal/mol. The compound 3d identified to possess pronounced biological potential towards the tested protein through the molecular docking studies, was subjected to in vitro (MTT) assay against MCF-7 cell line to explore its anticancer potential.

Thermodynamic stability and component heterogeneity of CO2/N2 mixed hydrates: Implications for hydrate-based CO2 capture and sequestration

Injecting CO2/N2 into marine sediments to form gas hydrates for CO2 storage is an emerging Carbon Capture and Storage (CCS) technology, holds the potential to significantly reduce the costs of CCS while simultaneously enhancing environmental persistence. However, there is currently a lack of comprehensive investigation into the critical parameters and stability evaluations of CO2/N2 mixed hydrates (Mix-H) formation. This study delves into the impact of gas-liquid ratios, pressure–temperature gradients, and hydrate formation degree on the phase equilibrium, formation kinetics, and thermodynamic stability of Mix-H. Experimental findings elucidate the excess water significantly enhances CO2 dissolution, increasing the thermodynamic barrier for Mix-H formation. Consequently, this leads to weakened kinetics and reduced total CO2 composition within the Mix-H (54.2%–96.4%). Raman spectroscopy confirmed varying heterogeneous compositions and thermodynamic stability of hydrate crystals within the bulk Mix-H. The heterogeneity is quantitatively assessed using a novel test – stepwise depressurization, which revealed increased heterogeneity with decreasing initial pressure–temperature as well as increasing gas-liquid ratios and hydrate formation degree. The heterogeneity of Mix-H significantly impacts the CO2 capture efficiency and long–term stability of CO2 sequestration under environmental disturbances. The results also pave the way for evaluating the performance of mixed hydrate applications in hydrate–based chemical engineering and CCS technology.

Short-Period Skyrmion Crystals in Itinerant Body-Centered Tetragonal Magnets

In this study, we investigate the stability of a magnetic skyrmion crystal with short-period magnetic modulations in a centrosymmetric body-centered tetragonal system. By performing the simulated annealing for the spin model, incorporating the effects of the biquadratic interaction and high-harmonic wave–vector interaction in momentum space, we find that the double-Q square skyrmion crystal consisting of two spin density waves is stabilized in an external magnetic field. We also show that double-Q states appear in both low- and high-field regions; the low-field spin configuration is characterized by an anisotropic double-Q modulation consisting of a superposition of the spiral wave and sinusoidal wave, while the high-field spin configuration is characterized by an isotropic double-Q modulation consisting of a superposition of two sinusoidal waves. Furthermore, we show that the obtained multiple-Q instabilities can be realized for various ordering wave vectors. The results provide the possibility of realizing the short-period skyrmion crystals under the body-centered tetragonal lattice structure.

Construction of activated carbon/activated carbon fibre capacitive deionization composite electrode and its potential application in desalination of brackish water

we constructed a novel capacitive deionization carbon/carbon composite electrode-activated carbon/activated carbon fibre (AC/ACF) with low-cost and low energy consumption and high desalination efficacy, and the desalination performance and energy consumption of the electrode under different processes, such as the electrode structure, the operating voltage, and the inlet flow rate, were investigated in comparison with those of the activated carbon (AC) and the activated carbon fibre (ACF) electrodes alone and the best operating parameters of the AC/ACF electrodes were optimized. The results showed that the oxygen-containing functional groups on the surface of AC/ACF increased, and the crystal stability was enhanced; the desalination rate and energy consumption of AC/ACF increased significantly with the increase of voltage, and the optimal operating parameters of AC/ACF were obtained through the entropy value Topsis function: operating voltage of 0.8 V, flow rate of 65 mL·min−1, energy consumption of 0.17 KWh·m−3, and desalination rate of 19.12 %. Further normalized analysis of the cost and energy consumption of the optimized process showed that the adsorption cost (0.11 $·g−1) and energy consumption of the AC/ACF composite were lower (0.45 Wh·gsalt−1), thus the AC/ACF material has the advantages of energy saving, low cost, and excellent desalination performance compared with other composites.