Energy Diffusion Research Articles

Application of a large wall electric probe (LWEP) for plasma and ambient gas studies

Abstract The operation of a large wall electric probe (LWEP) is analyzed, where the probe surface area in contact with the plasma is only a few times smaller than the area of the plasma boundaries. Compared to a small standard Langmuir probe (SLP), the LWEP may have significantly greater resolution and sensitivity, but could substantially perturb the plasma and distort the measured properties. A target application for the LWEP is where the sensitivity of the measurement is critical, but the effects of the plasma perturbation is minimal. A specific case where a LWEP may outperform a SLP is the measurement of a nonlocal electron distribution function at energies of electron free diffusion, that is, at energies significantly exceeding thermal electron energies, in order to obtain information about the parameters of the plasma or ambient gas. Examination of the LWEP analysis process has revealed that, depending on the plasma volume and probe configurations, it may be necessary to measure either the first or second derivatives of the probe current with respect to the probe potential to derive the energetic part of the electron energy distribution function.

Exploring size-dependent optical property alterations in fine-tuning intermetallic PdCd nanocube sizes.

Tuning the size of intermetallic nanocrystals is challenging due to the conflicting effects of surface free energy and surface diffusion on the disorder-to-order phase transition during wet-chemistry growth. Herein, we synthesized intermetallic PdCd nanocubes with tunable sizes ranging from 8 to 15 nm by adjusting the Cd precursor concentrations using a wet-chemistry approach. This process shares a mechanism of size tuning similar to quantum dot synthesis, involving the regulation of monomer concentration determined by the precursor concentrations. The intermetallic PdCd nanocubes exhibit distinct size-dependent optical properties compared to platinum group metal nanocrystals of similar size ranges, with increased light-induced catalytic enhancement as size increases. The 15 nm-sized nanocubes exhibited the most significant light-induced catalytic enhancement, reaching 3.3 times, while the 8 nm-sized nanocubes showed only a 1.6-fold enhancement in 4-nitrophenol reduction. This study emphasizes the importance of tuning the size of intermetallic nanocrystals, providing valuable insights for future exploration of their size-dependent properties.

The Importance of Energy Management in Public University Campuses

Energy consumption has gained great attention in recent years, particularly due to the changes in the geopolitics situation and the difficulty in ensuring security in energy sources supply. Several national and international governments set new and more stringent targets to reduce fossil fuel consumption, also proposing specific short-term and mid-term actions. For instance, the Italian Government emanates the Italian National Plan to Reduce Natural Gas consumption in 2022, particularly focused on residential, commercial and public buildings. University of L’Aquila takes inspiration from this planning, to revise its energy management and promote technical actions and a communication campaign aimed at reducing energy consumption. The short-term actions are related to the HVAC plants management of its building: a) shortening the heating days and reducing the daily hours HVAC switching on; b) slight reduction of the indoor comfort temperature; c) reduction of lighting time and intensity. Moreover, virtuous behavior has been encouraged with a communication campaign addressed to employees and students. Results obtained in only one year are very exciting: the natural gas consumption has been reduced more than 20% in academic year 2022/2023, with respect to average values of previous years, with an estimated GHG emissions avoided close to 140 tCO2 for the specific faculty considered. These results are very positive in the GreenMetric perspective, and they boost the importance also of a quite simple but effective energy management strategy and diffusion of awareness on energy and environmental issues.

Electrochemical Performance of MoB/Si3N4 Heterojunction as a Potential Anode Material for Li Ion Batteries.

In response to the current policy of high storage capacity, two-dimensional (2D) materials have revealed promising prospects as high-performance electrode materials. MoB, as a type of such material, is widely regarded as an anode candidate for Li-ion batteries due to its large specific surface area and abundant ion diffusion channels; the long-term cycling stability, however, is poor owing to material pulverization during the cycle. Therefore, MoB/Si3N4 heterojunction in this work is proposed as an anode material, with Si3N4 acting as a skeleton, maintaining the stability of the structure, while retaining the high energy storage properties of MoB as well. In addition, a certain built-in electric field is formed between them, which can play a role in regulating charge transfer, improving the ion transport channel, and accelerating the migration rate. Herein, the structural, electronic, and electrochemical properties are systematically investigated by first-principles calculations; the final results indicate that the heterojunction anode material does indeed have built-in electric fields, which promote the anode material to possess excellent electrical conductivity and outstanding electrochemical property. Meanwhile, the introduction of vacancy defects can bolster the diffusion kinetic performance of ion transport and greatly reduce the diffusion energy barrier of Li ions, which is conducive to the realization of rapid charge and discharge for the Li ion battery. Based on the synergistic effect of two single-component materials, the synthesized anode material displays a high theoretical capacity of 461 mAh/g, and the calculated open-circuit voltage is 0.66 V, within the range of the negative electrode criterion of 0-1 V, which can effectively play a role in preventing the formation of Li dendrites; these properties are comparable to other 2D anode materials as well. Given these intriguing properties, the MoB/Si3N4 heterojunction is an exceptional candidate for advanced LIB high-performance anode materials.

Investigations of Mechanisms Leading to Capacity Differences in Li/Na/K-Ion Batteries with Conversion-Type Transition-Metal Sulfides Anodes.

Conversion-type transition-metal sulfides (CT-TMSs) have been extensively studied as the anode of Li/Na/K-ion batteries due to their high theoretical capacity. An issue with the use of the material in the battery is that a large capacity difference is commonly observed. However, the underlying mechanism leading to the problem is still unknown. Here, the large capacity difference mechanisms of CT-TMSs anodes in the Li/Na/K-ion storage are elucidated, which arises from the difference in conversion degree and size of conversion products. Specifically, the increase in ionic radius will cause the increase in insertion-reaction ion diffuse energy barrier and conversion-reaction Gibbs free energies of phase transformation to decrease reaction kinetics, which causes a decrease in conversion degree and an increase in size of conversion products, thus leading to reduction in capacity. The increase in size and the decrease in the amount of conversion products inevitably reduce the amount of spin-polarized electrons injection into Fe and corresponding ions storage amount into sulfides during the ion-electron decoupling storage, thus reducing the capacity. The research clarifies the capacity difference mechanisms of CT-TMSs anodes in Li/Na/K storage, providing valuable insights for designing Li/Na/K storage high-capacity anodes.

Oxygen Vacancy-Electron Polarons Featured InSnRuO2 Oxides: Orderly and Concerted In-Ov-Ru-O-Sn Substructures for Acidic Water Oxidation.

Polymetallic oxides with extraordinary electrons/geometry structure ensembles, trimmed electron bands, and way-out coordination environments, built by an isomorphic substitution strategy, may create unique contributing to concertedly catalyze water oxidation, which is of great significance for proton exchange membrane water electrolysis (PEMWE). Herein, well-defined rutile InSnRuO2 oxides with density-controllable oxygen vacancy (Ov)-free electron polarons are firstly fabricated by in situ isomorphic substitution, using trivalent In species as Ov generators and the adjacent metal ions as electron donors to form orderly and concerted In-Ov-Ru-O-Sn substructures in the tetravalent oxides. For acidic water oxidation, the obtained InSnRuO2 displays an ultralow overpotential of 183 mV (versus RHE) and a mass activity (MA) of 103.02 A mgRu -1, respectively. For a long-term stability test of PEMWE, it can run at a low and unchangeable cell potential (1.56 V) for 200 h at 50 mA cm-2, far exceeding current IrO2||Pt/C assembly in 0.5 m H2SO4. Accelerated degradation testing results of PEMWE with pure water as the electrolyte show no significant increase in voltage even when the voltage is gradually increased from 1 to 5 A cm-2. The remarkably improved performance is associated with the concerted In-Ov-Ru-O-Sn substructures stabilized by the dense Ov-electron polarons, which synergistically activates band structure of oxygen species and adjacent Ru sites and then boosting the oxygen evolution kinetics. More importantly, the self-trapped Ov-electron polaron induces a decrease in the entropy and enthalpy, and efficiently hinder Ru atoms leaching by increasing the lattice atom diffusion energy barrier, achieves long-term stability of the oxide. This work may open a door to design next-generation Ru-based catalysts with polarons to create orderly and asymmetric substructures as active sites for efficient electrocatalysis in PEMWE application.

Improving ambient noise crosscorrelations using a polarization-based azimuth filter

Seismic interferometry is widely used to image and monitor earth structures at different scales by extracting an empirical Green’s function (EGF) from the crosscorrelation of ambient noise under the assumption of diffuse wavefields or energy equipartitioning. However, EGFs may be incorrectly estimated and lead to a misunderstanding of subsurface structures because the distribution of ambient noise sources is neither isotropic nor stationary. To extract reliable EGFs from the nonideal ambient noise data, we develop a polarization-based azimuth filter (PAF) to attenuate the ambient noise energy of nonstationary sources to improve the quality of crosscorrelation functions. The PAF is a time-frequency domain azimuth filter for 3C seismic data, which uses time-frequency polarization analysis to measure the azimuths of ambient noise signals and then filters the 3C data to obtain the signals from desired directions. Based on the stationary-phase theory, we use the PAF to extract the ambient noise signals from stationary-phase zones, which improves the quality of the crosscorrelation function and eliminates the requirement for long observations. A synthetic test and two short-time engineering examples demonstrate that uneven source distributions might cause serious spurious signals in EGFs, and we demonstrate the improvement in EGFs using our method. In addition, the PAF may allow for the complete separation of the fundamental and higher modes of Rayleigh waves, which uncovers more information implicit in the ambient noise data.

Ca-decorated holey graphyne for reversible hydrogen storage: Insights from DFT analysis

We theoretically examine the hydrogen storage capabilities of a newly synthesized carbon allotrope known as holey graphyne (HGY). HGY exhibits weak interaction with H2, making it unsuitable for storage, thus prompting surface modification. Ca binds to HGY with a binding energy of −2.03 eV and experiences a diffusion energy barrier of 1.49 eV. The supercell of HGY accommodates six Ca atoms, and each Ca atom binds five H2 with an average binding energy of −0.27 eV, resulting in an uptake capacity of 12.07 wt% and desorption temperature of 331K at 5 bar. AIMD simulation and positive phonon frequencies confirms thermal and dynamic stability of Ca-decorated HGY. RDG analysis reveals electrostatic interactions between Ca and HGY, and van der Waals interactions between H2 and Ca. Thus, Ca-decorated HGY shows exceptional uptake capacity, desirable adsorption energy and desorption temperature, making it a suitable material for on-board reversible hydrogen storage in light vehicles.

Enhanced water molecule sensitivity on defective WS2 monolayers through (ZnO)12 spherical nanocages decoration: A theoretical study

The adsorption of water molecules on sulfur vacancies (VS and V2S2) and gold atoms embedded in the sulfur vacancies (AuS) of tungsten disulfide (WS2) monolayers (ML) decorated with zinc-oxide (ZnO)12 nanocages were studied using dispersion-corrected density functional theory. Since the WS2 monolayer is predominantly inert, the introduction of defect states into the mid-bandgap region is significant due to its chemical and physical implications. The possibility of turning from an electron acceptor (p-type) to an electron donor (n-type) semiconductor character, when the sulfur vacancy density is varied or if the sulfur vacancies are filled with gold atoms, was demonstrated. The binding energy of the Au atom forming the AuS defect and the diffusion energy barrier from the VS defect to an adjacent site for Au were determined as 2.99 and 2.16 eV, respectively. Consequently, the substitutional defect AuS remains attached to the ML. The adsorption energy showed that the water molecule is chemisorbed on AuS defect on WS2 (n-type). Also, the density of states suggests a clear response as the chemiresistive sensor. Besides, how zinc-oxide spherical nanocages behave as sensors for different relative humidity levels was discussed. The response to water molecules was significantly enhanced by the chemisorption of the (ZnO)12 spherical nanocage on WS2-AuS. These composed systems formed WS2-ZnO heterojunctions with differences in the electronic structure. The study provides a comprehensive outlook on analyte interactions with WS2 (n-type) and WS2-ZnO surfaces, which have been utilized in the design of semiconductor gas sensors.

Strain engineering for optimized hydrogen storage: Enhancing ionic conductivity and achieving near-room-temperature desorption in Mg₂NiH₄

This study investigates strain engineering to optimize hydrogen storage in Mg₂NiH₄, with a focus on enhancing ionic conductivity and approaching room-temperature desorption. Using density functional theory (DFT), we analysed the effects of uniaxial and biaxial tensile and compressive strains on the structural, mechanical, diffusion kinetics, and electronic properties of Mg₂NiH₄. The activation energy for hydrogen diffusion was found to range from 0.38 to 0.45 eV under different strain conditions. The application of strain significantly influences ionic conductivity, with uniaxial strain resulting in values between 1.18 and 25.5 S/m, and biaxial strain yielding values from 12.3 to 18.3 S/m. Mechanical analysis shows that Mg₂NiH₄ exhibits brittle behaviour across all strain conditions. Additionally, electronic structure analysis indicates that the material maintains its metallic properties under both uniaxial and biaxial strain. Although the study did not achieve room-temperature desorption, it demonstrated significant progress, with desorption occurring at approximately 500 K. These results demonstrate that strain engineering can significantly improve ionic conductivity and facilitate hydrogen desorption closer to practical room temperature, providing valuable insights for optimizing Mg₂NiH₄ for practical hydrogen storage applications.

Synergistic Bimetallic Effects of BiSb Anodes Enable Long‐Stable Sodium Storage

AbstractAlloy‐type anodes are of interest for their resource‐rich and high theoretical capacity performance in sodium‐ion batteries (SIBs). However, severe volume expansion may lead to rapid capacity decay and electrode pulverization. In this work, metallic Bi with better structure stability is rationally selected as a skeleton to form a 2D BiSb alloy to alleviate the volume expansion. Interestingly, by combining in‐situ XRD and ex‐situ TEM characterizations, a reversible multi‐step alloying sodium storage mechanism of BiSb ↔ Na(Bi, Sb) ↔ Na3(Bi, Sb) in Bi0.4Sb0.6 anode is elucidated, and the partial amorphization and expanded interlayer spacing of BiSb alloy is also revealed, which greatly alleviate volume expansion thereby enhancing electrochemical stability. Furthermore, density functional theory and kinetic calculations demonstrate that Bi0.4Sb0.6 demonstrates lower Na+ adsorption energy and Na+ diffusion energy barriers, ensuring fast electron and ion transportation during sodium storage. Benefiting from the synergistic effects of binary alloy, Bi0.4Sb0.6 exhibits a high reversible capacity and cycling stability of 446 mAh g−1 at 0.1 A g−1, and 70% high capacity after 1100 cycles at 0.5 A g−1. This work provides new insights and opportunities to develop advanced precise alloy‐type anode materials for SIBs.

Adsorption and evolution of N2 molecules over ZnO monolayer: a combined DFT and kinetic Monte-Carlo insight

A large surface area, wide band gap, and unique bonding property between Zn and O atoms make the hexagonal ZnO monolayer attractive as a gas sensor. In the present work, the adsorption and evolution of nitrogen (N2) molecules over a ZnO monolayer have been studied using two different theoretical methods: van der Waals density functional theory (vdW-DFT) and kinetic Monte-Carlo (kMC) simulation. The adsorption and diffusion (hopping over the surface) energy of a N2 gas molecule has been calculated considering the different sites over the ZnO substrate using the revPBE-vdW functional. Bader charge, electron localization function analysis, density of states and band structure plotting have been used to understand the adsorption mechanism. Lateral repulsive interaction between two N2 molecules limits the maximum packing number of gas molecules within one hexagonal ring. The output of the vdW-DFT calculation has been fed to the kMC code to predict the rate of adsorption, desorption, and diffusion, along with the overall surface coverage at different temperatures and pressures. Finally, the change in the N2 adsorption energy has been predicted with the increase of the ZnO layer number.

Effect of Sulfurization Temperature on Properties of Cu2ZnSnS4 Thin Films and Diffusion of Ti Substrate Elements

The addition of flexible Cu2ZnSnS4 (CZTS) thin film solar cells to titanium (Ti) substrates is an attractive way to achieve the low-cost manufacturing of photovoltaics. Prior research has indicated that the appropriate diffusion of Ti elements can enhance the crystalline growth of CZTS films. However, the excessive diffusion of Ti has been shown to adversely affect the photovoltaic performance of CZTS photovoltaic devices. Therefore, it is essential to regulate the diffusion of Ti elements within CZTS thin films to optimize their photovoltaic properties. The tendency for Ti substrate elements to diffuse into CZTS films is also influenced by the activation energy associated with these Ti elements. The sulfurization temperature is posited to be a critical factor in modulating the diffusion and activation energy of Ti elements within CZTS thin films. Consequently, this research investigates the alteration of the sulfurization temperature of CZTS thin films in order to enhance the properties of these thin films and to examine the diffusion behavior of titanium elements. The results reveal that as the sulfurization temperature increases, the diffusion of Ti elements within the CZTS thin films initially increases, then decreases, and subsequently increases again. This pattern suggests that the diffusion of Ti elements is affected not only by the activation energy of the Ti elements but also by the defect hopping distance within the CZTS thin films. Notably, at a sulfurization temperature of 550 °C, the grains at the base of the CZTS thin film demonstrate an increased density, which is associated with a reduced defect hopping distance, thereby hindering the diffusion of Ti elements within the CZTS thin films. Furthermore, at this specific sulfurization temperature, the slope of the current–voltage (I–V) curve for the CZTS/Ti structure reaches its maximum, indicating optimal ohmic contact characteristics.

Tuning the electrochemical performance of a biphenylene coated metal as the anode for K+-ion batteries

The researchers employed density functional theory (DFT) computations to assess suitability of BP-biphenylene (b-BP) monolayers for application in potassium-ion battery systems. In their evaluations, the researchers considered various factors, like adsorption energy (Ead) of the b-BP monolayer with adsorbed potassium adatoms, in addition to diffusion energy barrier (Ebar) and storage capacity and of potassium ions on this surface. The results indicated that the b-BP monolayer has significantly higher potassium-ion storage capacities, reaching 1026 mAh/g, compared to typical graphite anodes and other carbon materials. The Ebar for potassium ions on the b-BP monolayer was determined to be 0.22 eV. Furthermore, anticipated open-circuit voltage (OCV) values for this material were found to lie within acceptable range of 0.25–1.2 V, making it suitable for use as an anode. These research findings underscore the potential of the b-BP monolayer as an appropriate anode material for potassium-ion battery (KIBs) applications.

Six-Membered Ring Directed Assembly of a Zirconium Zeolitic Metal-Organic Framework for Efficient Separation of Hexane Isomers.

The synthesis of zirconium MOFs with zeolite net is quite challenging due to the high connectivity of Zr6 clusters, which is far from tetrahedral connection, a requisite for zeolite net. In this work, we demonstrate a six-membered ring (6MR) strategy through mimicking of mineral zeolites with mixed ditopic and tritopic carboxylate linkers. With this strategy, the ditopic linker cross-links Zr6 clusters to form 4-connected zeolite-like nets, while the tritopic one is used to direct the formation of 6MR and simultaneously consumes extra coordination sites on the cluster. The feasibility of this strategy is shown by one zeolitic metal-organic framework (NNM-5) and this strategy has also led to the synthesis of the other dia-type zirconium MOF (NNM-6). Interestingly, as the tritopic linker not only directs the formation of 6MR but also partitions 6MR into small segments, NNM-5 with SOD topology shows a structural feature of small aperture and big cage, which has led to efficient separation of hexane isomers. With both exceptionally high n-hexane uptake (65.9 cm3 g-1) and size-exclusion selectivity, an exceptional separation capability is verified by breakthrough experiments. Calculation results demonstrate that the large difference of diffusion energy barrier due to the small aperture accounts for the underlying separation mechanism.

Molecular simulation study of adsorption-diffusion of CH4, CO2 and H2O in gas-fat coal

In order to clarify the microscopic dynamics mechanism of CH4, CO2 and H2O adsorption and diffusion in coal, and to reveal the mechanism of the influence of different temperatures and pressures on the adsorption and diffusion characteristics of coal adsorbed CH4, CO2 and H2O molecules. In this paper, the macromolecular structure model of Jixi gas-fat coal was constructed, based on the Giant Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) methods. The adsorption-diffusion characteristics of CH4,CO2 and H2O single-component gases in the gas-fat coal macromolecule model at temperatures ranging from 273.15 K to 313.15 K and pressures ranging from 0.01 MPa to 15 MPa were investigated by using Material Studio software. The research results indicated that: The adsorption of three gases, CH4, CO2 and H2O, increased with the increase of equilibrium pressure, and the adsorption isotherms conformed to Langmuir type I isotherms. The amount of saturated adsorption of CH4 ranged from 11.18 to 14.37 ml/g, the saturated adsorption of CO2 ranged from 20.40 to 24.70 ml/g, and the saturated adsorption of H2O ranged from 66.61 to 84.21 ml/g. With the increase of temperature, the saturated adsorption of CH4 and CO2 both decreased, and the saturated adsorption of H2O firstly increased and then decreased, and the adsorption of H2O by low temperature and high temperature had both an inhibitory effect on the adsorption of H2O. The potential energy distributions of CH4, CO2 and H2O molecules are poisson distributed. The absolute values of the most available interaction energies are, from highest to lowest: H2O > CO2 > CH4; the activation energies for diffusion of CH4, CO2 and H2O are 12.20 kJ/mol, 3.36 kJ/mol, and 8.47 kJ/mol, respectively, and the diffusion of CO2 is the more likely to occur. The adsorption of CH4 and CO2 in coal is physical adsorption, while the adsorption process of H2O molecules is beyond the scope of physical adsorption. The absolute value of the interaction energy is H2O > CO2 > CH4 in descending order.

Optimization of Low-Pressure Turbine Blade by Means of Fine Inspection of Loss Production Mechanisms

Abstract In this study, Proper Orthogonal Decomposition (POD) was applied to Large Eddy Simulations (LES) of two high-loaded low-pressure turbine cascades under unsteady inflow conditions to investigate entropy production within different parts of the blade passage. The terms for Turbulent Kinetic Energy (TKE) production, diffusion, and dissipation from the stagnation pressure transport equation were integrated across the computational domain. The POD-based method enables the decomposition of contributions from various coherent flow dynamics to TKE production and dissipation, such as the migration, bowing, tilting, and reorientation of incoming wake filaments, as well as the breakdown of streaky structures in the blade boundary layer and the formation of Von Karman vortices in the blade wake. This approach helps designers identify the dominant POD modes (i.e., turbulent flow structures) responsible for loss generation, understand their dynamics and locate where they primarily act. Using this optimization strategy, a new low-pressure turbine profile was designed. LES calculations on the optimized geometry showed that it is possible to design a higher-loaded profile with a lower global loss coefficient. The new loading distribution, characterized by stronger acceleration in the early part of the blade passage, results in reduced upstream wake migration losses and lower TKE production in the trailing edge wake zone due to early suction side boundary layer transition.

Enhanced Photocatalytic Degradation Performance by Micropore-Confined Charge Transfer in Hydrogen-Bonded Organic Framework-Like Cocrystals.

Carrier utilization in organic photocatalytic materials is unsatisfactory due to the large exciton binding energy and short exciton diffusion length. Both donor-acceptor (D-A) strategies and porous designs are promising approaches to improve carrier utilization in photocatalysts. However, a more efficient way is to shorten the distance of exciton migration to the catalyst surface by the charge transfer (CT) process. Herein, hydrogen-bonded organic framework-like cocrystal (NDI-Cor HOF-cocrystal) is prepared with novel structures serving as a proof of concept for the approach, using N, N'-bis (5-isophthalate) naphthalimide (NDI-COOH) as the porous framework and acceptor, and Coronene (Cor) as the donor unit. CT and porous engineering are integrated through cocrystal strategy. Under light irradiation, photogenerated excitons transfer and dissociate from the inner surface of the micropores on a hundred-picosecond time scale, where efficient radical transformation and further redox reactions with adsorbed phenol molecules occur. NDI-Cor HOF-cocrystal photocatalytic degradation of phenol is 15 times higher than that of original HOFs, and achieves near 90% deep mineralization of phenol. Significantly, this work has designed novel HOF-cocrystal and also provides new modification strategies for high performance organic photocatalysts.

Nanostructure and dislocation interactions in refractory complex concentrated alloy: From chemical short-range order to nanoscale B2 precipitates

Refractory complex concentrated alloys (RCCAs) have emerged as a promising class of structural materials, demonstrating exceptional mechanical performance in aggressive environments. However, the complex atomic environments, significant lattice distortion, and vast compositional space of RCCAs present challenges to understanding the mechanisms that govern structure-property relationships. In this study, we explore the dislocation mechanisms in three model quaternary RCCAs, namely Mo25Nb10Ta25W40 (at. %), Mo25Nb25Ta25W25, and Mo25Nb40Ta25W10 using large-scale atomistic simulations and machine learning based Spectral Neighbor Analysis Potential. Our atomistic simulations examine how the chemical composition and local ordering influence the mobility of both edge and screw dislocations, and how lattice distortion and diffuse anti-phase boundary energy (DAPBE) affect dislocation behaviors during nanostructural evolution. Notably, with the increase in Nb concentration in the model RCCAs, both DAPBE and lattice distortion are simultaneously enhanced as the chemical short-range order (CSRO) evolves into nanoscale B2 precipitates. This evolution results in high lattice distortion due to the lattice mismatch between B2 precipitates and the random matrix. Consequently, B2 nanoprecipitates provide a stronger pinning effect, hindering edge dislocation motion while promoting cross-slip of screw dislocations, leading to a reduced screw-to-edge ratio in slip resistance and mobility discrepancy. These findings offer valuable insights into dislocation behaviors and interactions with ordered precipitates, highlighting the importance of exploring non-equiatomic compositions and advancing beyond CSRO in RCCAs. This study has implications for optimizing alloy compositions and processing methods for superior performance in aggressive environments.

AB–stacked bilayer β12–borophene as a promising anode material for alkali metal-ion batteries

As the lightest 2D material, monolayer borophene exhibits a specific charge capacity of 1860 mA h g−1 for Li-ion batteries, which is four times higher than that of graphite and is one of the highest specific charge capacities ever reported for 2D anode materials. Additionally, it showed high mechanical strength and a low diffusion barrier. However, monolayer borophene suffers from stability issues in its free-standing form, which restricts its real-life applications. Inspired by the recent experimental investigations, which proved the higher stability of bilayer borophene polymorphs (BBPs) over their monolayer counterparts, in this work, we investigated the dynamical and thermodynamical stabilities of both AA– and AB–stacked BBPs in their β12 phase using first-principles calculations. Between the two stacking patterns, we found that only the AB–stacked β12–BBP is both energetically and dynamically stable, and we further investigated its potential as a high-performance anode material for alkali metal-ion batteries. Our investigations show that AB–stacked β12–BBP exhibits good electrical conductivity before and after metal atom (Li/Na/K) adsorption onto it. Further, AB–stacked β12–BBP adsorbs the metal atoms strongly with adsorption energies ranging between −0.89 to −1.44 eV, indicating that there is a lesser possibility of forming dendrites on this anode. Similarly, it has a low diffusion energy barrier (~ 0.13–0.49 eV) for metal atoms, meeting the fast charge/discharge rate requirements. Moreover, it exhibits a reasonably low average metal-insertion voltage (0.43 to 0.65 V) and a specific charge capacity of 330–413 mA h g−1 that is comparable to graphite. All the above findings suggest that the AB–stacked bilayer β12– borophene can be a potentially favorable anode material.