High-Temperature Superconductivity in Perovskite Hydride Below 10 GPa.

Hydrogen and hydride materials have long been considered promising materials for high-temperature superconductivity. However, the extreme pressures required for the metallization of hydrogen-based superconductors limit their applications. Here, a series of high-temperature perovskite hydrides is designed that can be stable within 10 GPa. The research covered 182 ternary systems and ultimately determined that eight new compounds are stable within 20 GPa, of which five exhibited superconducting transition temperatures exceeding 120 K within 10 GPa, including KGaH3 (146 K at 10 GPa), RbInH3 (130 K at 6 GPa), CsInH3 (153 K at 9 GPa), RbTlH3 (170 K at 4 GPa) and CsTlH3 (163 K at 7 GPa). Excitingly, KGaH3 and RbGaH3 are thermodynamically stable at 50 GPa. Among these perovskite hydrides, alkali metals are responsible for providing a fixed amount of charge and supporting alloy framework composed of hydrogen and IIIA group elements to maintain stable crystal structure, while the cubic hydrogen alloy framework formed by IIIA group elements and hydrogen is crucial for high-temperature superconductivity. This work will inspire further experimental exploration and take an important step in the exploration of low-pressure stable high-temperature superconductors.

Evolutionary Pathways of T-Phase Transition Metal Dichalcogenides: A Comprehensive Study of PtxSey Clusters.

Understanding the transition from nonplanar to planar clusters is crucial for the controllable synthesis of transition metal dichalcogenide (TMDC) monolayers. Using PtSe2 as a model, we investigate how the chemical environment influences the nucleation and growth stages of monolayer PtSe2 through structure searching and first-principles calculations. We established a comprehensive database of platinum selenide clusters (PtxSey, x = 1-10), analyzing 2095 unique clusters and identifying 191 stable isomers and 63 structures with the lowest formation energy on the convex hull. Our findings reveal a chemical environment-dependent phase transition from 3D structures to the planar T-phase of PtxSey clusters, representing an evolutionary route for PtSe2 growth. Clusters such as PtSe6, Pt2Se9, Pt3Se10, and Pt7Se10 in Pt-rich environments, as well as Pt2Se15 and Pt10Se32 in Se-rich environments, have been found to exhibit high stability. Additionally, the impact of varying chemical potentials of Pt and Se on the stability of these clusters is explored. PtSe4 and PtSe6 are found to be highly stable under most experimentally achievable chemical potential conditions and may serve as dominant precursors during PtSe2 growth. This work advances our understanding of the nucleation processes of PtSe2 and other T-phase TMDC materials.

Adsorptive Shield Derived Cathode Electrolyte Interphase Formation with Impregnation on LiNi0.8Mn0.1Co0.1O2 Cathode: A Mechanism-Guiding-Experiment Study.

Lithium difluoro(oxalate) borate (LiDFOB) contributes actively to cathode-electrolyte interface (CEI) formation, particularly safeguarding high-voltage cathode materials. However, LiNixCozMnyO2-based batteries benefit from the LiDFOB and its derived CEI only with appropriate electrolyte design while a comprehensive understanding of the underlying interfacial mechanisms remains limited, which makes the rational design challenging. By performing ab initio calculations, the CEI evolution on the LiNi0.8Co0.1Mn0.1O2 has been investigated. The findings demonstrate that LiDFOB readily adheres to the cathode via semidissociative configuration, which elevates the Li deintercalation voltage and remains stable in solvent. Electrochemical processes are responsible for the subsequent cleavage of B-F and B-O bonds, while the B-F bond cleavage leading to LiF formation is dominant in the presence of adequate Li+ with a substantial Li intercalation energy. Thus, impregnation is established as an effective method to regulate the conversion channel for efficient CEI formation, which not only safeguards the cathode's structure but also counters electrolyte decomposition. Consequently, in comparison to utilizing LiDFOB as an electrolyte additive, employing LiDFOB impregnation in the NCM811/Li cell yields significantly improved cycling stability for over 2000 h.

Language Model-Assisted Machine Learning, Photoelectrochemical, and First-Principles Investigation of Compatible Solvents for a CH3NH3PbI3 Film in Water.

Machine learning and data-driven methods have attracted a significant amount of attention for the acceleration of the design of molecules and materials. In this study, a material design protocol based on multimode modeling that combines literature modeling, numerical data collection, textual descriptor design, genetic modeling, experimental validation, first-principles calculation, and theoretical efficiency calculation is proposed, with a case study on designing compatible complex solvent molecules for a halide perovskite film, which is notorious for optoelectronic deactivation under hostile conditions, especially in water. In the multimode modeling design process, the textual descriptors play the central role and store rich literature scientific knowledge, which starts from the construction of a high-dimension literature model based on scientific articles and is realized by a genetic algorithm for materials predictions. The prediction is substantiated by follow-up experiments and first-principles calculations, leading to the successful identification of effective molecular combinations delivering an unprecedented large aqueous photocurrent (increasing by 3 orders of magnitude compared with that of CH3NH3PbI3) and remarkable aqueous stability (improving from 36% to 89% after immersion in water) under the hostile condition. This study provides a practical route via multimode modeling for accelerating the design of molecule-modified and solution-processed materials in a real scenario.

Theoretical Optimization of an Earth-Abundant and Environmentally Friendly Photovoltaic Absorber Cu3PSe4 from First-Principles Study to Device Simulation.

To seek an earth-abundant and environmentally friendly absorber for thin-film solar cells, Cu3PSe4 is investigated by first-principles calculations and device simulations. We demonstrate that the compound has a suitable band gap width of 1.3 eV as well as a high sunlight absorption coefficient. However, drawbacks like small electron affinity, high hole concentration, large lattice mismatch with CdS, etc., are revealed, which may degrade the photovoltaic performance. To address those shortcomings, we propose (1) to optimize the carrier concentration by preparing the samples at low temperature and under a Cu-rich environment, (2) to replace the CdS buffer layer by a more suitable wide-gap semiconductor with smaller lattice mismatch, and (3) that the selected buffer layer should have small electron affinity in order to reduce the open-circuit voltage losses. After implementation of these optimization approaches, the device simulations demonstrate that the power conversion efficiency reaches 17.7% for a solar cell with the configuration Mo/Cu3PSe4/WS2/n-ZnO. The combination of first-principles calculations at the atomistic level and device simulations at the macroscopic level provides an appropriate approach to design ideal solar cells.

Solving the Asymmetric Doping for Wide-Gap Semiconductors by Host Functionalization: Quantum Engineering Strategy.

Asymmetric doping of wide-gap semiconductors has long been a major challenge, hindering their wider applications. Despite numerous attempts to address this issue through engineering doping levels, the results were still inconclusive. In this work, we propose a quantum engineering strategy based on the state-of-the-art spin-polarized HSE06 hybrid functional method. The local band offset between the host and quantum structures can considerably compensate for the large carrier activation energy (Ea). We chose the system of the AlN host embedded by GaN quantum dots as an example to validate the feasibility of this strategy. The Ea of Si (n-type) and Be (p-type) dopants can be reduced from 222 and 404 meV to negative values and 2 meV, respectively. Therefore, electron and hole density can be increased to more than 1019 and 1020 cm-3, respectively. We also tested potential dopants (C and Ge for the n-type, Mg and Ca for the p-type), and the technique is equally effective. This mechanism can also be used to understand the experimental observations of the superlattice doping strategy. Overall, our study demonstrates that the quantum engineering strategy provides a potential solution to overcome the asymmetric doping problem for universal wide-gap semiconductors and supports a feasible pathway for more efficient devices in the future.

Robust massless Dirac fermions in hydro-/halogenated trigonal borophene.

The striking electronic characteristics of graphene trigger immense interests and continual explora-tions for new two-dimensional (2D) Dirac materials. By first-principles electronic structure calculations, we here identify a new set of 2D semimetals in hydro-/halogen embedding trigonalδ6borophene, namelyδ6-B3X (X = H, F, Cl), that possess the graphene-like massless Dirac fermions. Owing to the central hollow B atoms strongly hybridized to the hydro-/halogen adatoms, adequate charge transfer is induced from the hollow B to the basal honeycomb B sublattice, which electronically stabilizes the 2D sheet and decisively endows a robust (intrinsic and stable-against-strains) graphene-like Dirac cone state. The predicted high energetic, dynamic and thermal stabilities, combined with pretty geometrical match to the commonly utilized Ag/Au(111) substrates, support their experimental viabilities. Our prediction provides a new branch for exploring the intriguing 2D Dirac fermionic states in versatile boron element and its derivatives.

Pressure-induced magnetic and topological transitions in non-centrosymmetric MnIn2Te4.

In recent years, the study of magnetic topological materials, with their variety of exotic physics, has significantly flourished. In this work, we predict the interplay of magnetism and topology in the non-centrosymmetric ternary manganese compound MnIn2Te4under external hydrostatic pressure, using first-principles calculations and symmetry analyses. At ambient pressure, the ground state of the system is an antiferromagnetic insulator. With the application of a small hydrostatic pressure (∼0.50 GPa), it undergoes a magnetic transition, and the ferromagnetic state becomes energetically favorable. At ∼2.92 GPa, the ferromagnetic system undergoes a transition into a Weyl semimetallic phase, which hosts multiple Weyl points in the bulk. The presence of non-trivial Weyl points have been verified by Wilson bands computations and the presence of characteristic surface Fermi arcs. Remarkably, we discover that the number of Weyl points in this system can be controlled by pressure and that these manifest in an anomalous Hall conductivity (AHC). In addition to proposing a new candidate magnetic topological material, our work demonstrates that pressure can be an effective way to induce and control topological phases, as well as AHC, in magnetic materials. These properties may allow our proposed material to be used as a novel pressure-controlled Hall switch.

Insight into the electronic, elastic, structural, thermal, and optical characteristics of potassium magnesium fluoride KMgF3 with isotropic external stress.

The demand for increasingly fine detail in optical lithography for semiconductors necessitates the use of lower-wavelength lithographic light. This drives the need for lenses in optical lithography steppers made of vacuum ultraviolet-transparent (VUV-transparent) materials. In this work, the density functional theory (DFT) study of potassium magnesium fluoride KMgF3 is presented. Total energy was calculated with correlation functional generalized gradient approximation (GGA). The ground state quantities such as bulk modulus and lattice parameters have been evaluated. The material's cubic structure is scrutinized under various stress levels (0-100 GPa), revealing that KMgF3 starts to deform at 128 GPa. The C11, C12, and C44 independent elastic constants were used to analyze the structural stability of the KMgF3. The densities of states and electronic band structures have also been computed. According to electronic calculations, when stress is applied to KMgF3, the band gap increases for all values of stress (0-100 GPa). Mechanical parameters, including elastic constants and ratios, indicate the material's remarkable ductility and stability. Phonon density of states and thermal characteristics exhibit shifts and variations with increasing stress, providing insights into the material's behaviour below its melting point. The thermodynamic properties of KMgF3, such as enthalpy, free energy, entropy, heat capacity, and Debye temperatures at various temperatures ranging from 0 K to 1000 K, have also been examined to explore their basic properties. These findings contribute to a comprehensive understanding of KMgF3, opening avenues for its application in advanced technologies, particularly in the realms of semiconductors and optoelectronics.

First-principles calculations on dislocations in MgO.

While ceramic materials are widely used in our society, their understanding of the plasticity is not fully understood. MgO is one of the prototypical ceramics, extensively investigated experimentally and theoretically. However, there is still controversy over whether edge or screw dislocations glide more easily. In this study, we directly model the atomic structures of the dislocation cores in MgO based on the first-principles calculations and estimate the Peierls stresses. Our results reveal that the screw dislocation on the primary slip system exhibits a smaller Peierls stress than the edge dislocation. The tendency is not consistent with metals, but rather with TiN, suggesting a characteristic inherent to rock-salt type materials.

Performing highly accurate computational methods ­ specifically, a combination of direct atomic modeling and first-principles calculations ­ to estimate the Peierls stresses of MgO.

First Principles Calculation of the Effect of Cu Doping on the Mechanical and Thermodynamic Properties of Au-2.0Ni Solder.

To meet the demands for high-temperature performance and lightweight materials in aerospace engineering, the Au-Ni solder is often utilized for joining dissimilar materials, such as Ti3Al-based alloys and Ni-based high-temperature alloys. However, the interaction between Ti and Ni can lead to the formation of brittle phases, like Ti2Ni, TiNi, and TiNi3, which diminish the mechanical properties of the joint and increase the risk of crack formation during the welding process. Cu doping has been shown to enhance the mechanical properties and high-temperature stability of the Au-Ni brazed joint's central area. Due to the difficulty in accurately controlling the solid solution content of Cu in the Au-Ni alloy, along with the high cost of Au, traditional experimental trial-and-error methods are insufficient for the development of Au-based solders. In this study, first principles calculations based on density functional theory were employed to analyze the effect of Cu content on the stability of the Au-2.0Ni-xCu (x = 0, 0.25, 0.5, 0.75, 1.0, 1.25 wt%) alloy phase structure. The thermal properties of the alloy were determined using Gibbs software fitting. The results indicate that the Au-2.0Ni-0.25Cu alloy exhibits the highest plastic toughness (B/G = 5.601, ν = 0.416, Cauchy pressure = 73.676 GPa) and a hardness of 1.17 GPa, which is 80% higher than that of Au-2.0Ni. This alloy balances excellent strength and plastic toughness, meeting the mechanical performance requirements of brazed joints. The constant pressure specific heat capacity (Cp) of the Au-2.0Ni-xCu alloy is higher than that of Au-2.0Ni and increases with Cu content. At 1000 K, the Cp of the Au-2.0Ni-0.25Cu alloy is 35.606 J·mol-1·K-1, which is 5.88% higher than that of Au-2.0Ni. The higher Cp contributes to enhanced high-temperature stability. Moreover, the linear expansion coefficient (CTE) of the Au-2.0Ni-0.25Cu alloy at 1000 K is 8.76 × 10-5·K-1, only 0.68% higher than Au-2.0Ni. The lower CTE helps to reduce the risk of solder damage caused by thermal stress. Therefore, the Au-2.0Ni-0.25Cu alloy is more suitable for brazing applications in high-temperature environments due to its excellent mechanical properties and thermal stability. This study provides a theoretical basis for the performance optimization and engineering application of the Au-2.0Ni-xCu alloy as a gold-based solder.

LiNbO3 and LiTaO3 Coating Effects on the Interface of the LiCoO2 Cathode: A DFT Study of Li-Ion Transport.

In solid-state batteries, the interface between cathodes and solid electrolytes is crucial and coating layers play a vital role. LiNbO3 has been known as a promising coating material, whereas recent studies showed its degradation via releasing oxygen and lithium during cycling. This computational study addresses the elucidation of essential characteristics of the coating materials by examining LiNbO3 and its counterpart LiTaO3 interfaces to a representative layered cathode, LiCoO2. Employing the interface CALYPSO method, we constructed explicit models of both coatings on LiCoO2. Our findings indicate that LiTaO3 offers easier Li+ migration at the interface due to the smaller difference in Li adiabatic potential at the interface, whereas LiNbO3 more effectively suppresses oxygen activity at high delithiation states via lowering the O 2p states. This comparative analysis provides essential insights into optimizing coating materials for improved battery performance.

Excellent Hole Mobility and Out-of-Plane Piezoelectricity in X-Penta-Graphene (X = Si or Ge) with Poisson's Ratio Inversion.

Recently, the application of two-dimensional (2D) piezoelectric materials has been seriously hindered because most of them possess only in-plane piezoelectricity but lack out-of-plane piezoelectricity. In this work, using first-principles calculation, by atomic substitution of penta-graphene (PG) with tiny out-of-plane piezoelectricity, we design and predict stable 2D X-PG (X = Si or Ge) semiconductors with excellent in-plane and out-of-plane piezoelectricity and extremely high in-plane hole mobility. Among them, Ge-PG exhibits better performance in all aspects with an in-plane strain piezoelectric coefficient d11 = 8.43 pm/V, an out-of-plane strain piezoelectric coefficient d33 = -3.63 pm/V, and in-plane hole mobility µh = 57.33 × 103 cm2 V-1 s-1. By doping Si and Ge atoms, the negative Poisson's ratio of PG approaches zero and reaches a positive value, which is due to the gradual weakening of the structure's mechanical strength. The bandgaps of Si-PG (0.78 eV) and Ge-PG (0.89 eV) are much smaller than that of PG (2.20 eV), by 2.82 and 2.47 times, respectively. This indicates that the substitution of X atoms can regulate the bandgap of PG. Importantly, the physical mechanism of the out-of-plane piezoelectricity of these monolayers is revealed. The super-dipole-moment effect proposed in the previous work is proved to exist in PG and X-PG, i.e., it is proved that their out-of-plane piezoelectric stress coefficient e33 increases with the super-dipole-moment. The e33-induced polarization direction is also consistent with the super-dipole-moment direction. X-PG is predicted to have prominent potential for nanodevices applied as electromechanical coupling systems: wearable, ultra-thin devices; high-speed electronic transmission devices; and so on.

The effect of strain effect on WS2 monolayer as a potential delivery carrier for anti-myocardial infarction drug: First-principles study.

CONTEXT: Myocardial infarction is one of the major health challenges. It is of great significance to develop potential delivery carriers for new anti-myocardial infarction drugs. In this paper, based on first-principles calculations, monolayer WS2 with excellent photoelectric properties was verified as a carrier for the anti-myocardial infarction drug amiodarone (AMD). Studies have shown that the WS2-adsorbed AMD system (WS2@AMD) maintains structural stability and produces an adsorption energy of-2.12 eV. Mulliken charge analysis shows that electrons are transferred from WS2 atoms to AMD atoms. Among them, C, N and O obtained the maximum values of 0.51,0.37 and 0.56 e electrons, respectively, while H and I lost the maximum values of 0.32 and 0.24 e electrons, respectively. The optical response of WS2 adsorbed AMD system is similar to that of WS2. The light absorption coefficients of the two materials in the near ultraviolet region and the visible region can reach the order of 105 cm-1 and 104 cm-1, and the strain makes the light absorption peak red-shifted. The feasibility of temperature-controlled release mechanism of WS2 as AMD carrier was discussed. This theoretical work helps to improve the performance of two-dimensional nanomaterials and make them better as drug delivery carriers to improve the therapeutic effect of myocardial infarction. These results indicate that the WS2 monolayer has potential applications in the development of drug delivery carriers. METHODS: In this study, based on first-principles calculations, the CASTEP simulation software package was used to study the structure and properties of materials. The interaction between electrons and ions is considered by using Ultrasoft pseudopotentials. In order to eliminate the spurious interaction between adjacent structures caused by periodic calculations, a vacuum space no less than 18 Å is placed in the vertical direction if necessary. Different functions may produce different density functional calculation results. Due to the low sensitivity of the crystal structure to the calculation details, the PBE functional under the generalized gradient approximation (GGA) was initially used for structural optimization, and the energy cutoff value was set to 500 eV. Grimme 's dispersion correction was used to make the results more accurate. The Brillouin zone (BZ) is sampled by a 7 × 7 × 1 K-point grid to ensure the reliability of the original lattice calculation. The lattice vector and atomic coordinates are relaxed, and the tolerance of each atom is less than 0.01 eV/Å. The energy tolerance at the atomic position is less than 10-7 eV/atom. When calculating the band gap, the HSE06 hybrid functional is used to modify the optimized structure of the PBE functional to obtain more accurate results. Spin-polarized DFT calculations were performed to calculate the electronic structure.

Uncovering the Interfacial Strengthening Mechanisms of α-Mg/Mg2Sn/ß-Li Interfaces Using First-Principle Calculations and HAADF-STEM.

Previously, we reported our new invention of an ultralight (ρ = 1.61 g/cm3) and super high modulus (E = 64.5 GPa) Mg-Li-Al-Zn-Mn-Gd-Y-Sn (LAZWMVT) alloy. Surprisingly, the minor additions of Sn contribute to significant strength and stiffness increases. In this study, we found that Mg2Sn was not only the simple precipitate but also acted as the glue to bind the α-Mg/ß-Li interface in a rather complicated way. To explore its mechanism, we have performed first-principle calculations and HAADF-STEM experiments on the interfacial structures. It was found that the interfacial structural models of α-Mg/ß-Li, α-Mg/Mg2Sn, and ß-Li/Mg2Sn composite interfaces prefer to form α-Mg/Mg2Sn/ß-Li ternary composite structures due to the stable formation enthalpy (ΔH: -1.95 eV/atom). Meanwhile, the interface cleavage energy and critical cleavage stress show that Mg2Sn contribute to the interfacial bond strength better than the ß-Li/α-Mg phase bond strength (σb(ß-Li/Mg2Sn): 0.82 GPa > σb(α-Mg/Mg2Sn): 0.78 GPa > σb(ß-Li/α-Mg): 0.62 GPa). Based on the interfacial electronic structure analysis, α-Mg/Mg2Sn and ß-Li/Mg2Sn were found to have a denser charge distribution and larger charge transfer at the interface, forming stronger chemical bonds. Additionally, according to the crystal orbital Hamiltonian population analysis, the bonding strength of the Mg-Sn atom pair was 2.61 eV, which was higher than the Mg-Li bond strength (0.39 eV). The effect of the Mg2Sn phase on the stability and interfacial bonding strength of the alloying system was dominated by the formation of stronger and more stable Mg-Sn metal covalent bonds, which mainly originated from the contribution of the Mg 3p-Sn 5p orbital bonding states.

Main group metal elements enhance electrochemical nitrogen reduction reaction of vanadium-based single atom catalysts through d-p orbital hybridization.

Developing active sites with flexibility and diversity is crucial for single atom catalysts (SACs) towards sustainable nitrogen fixation at ambient conditions. Herein, the effects of doping main group metal elements (MGM) on the stability, catalytic activity, and selectivity of vanadium-based SACs is systematically investigated based on density functional theory calculations. It is found that the catalytic activity of V site can be significantly enhanced by the synergistic effect between MGM and vanadium atoms. More importantly, a volcano curve between the catalytic activity and the adsorption free energy of NNH* can be established, in which V-Pb dimer embedded on N-coordinated graphene (VPb-NG) exhibits optimal NRR activity due to its location at the top of volcano. Further analysis of electronic structures reveals that the unoccupancy ratio (eg/t2g) of V site is dramatically increased by the strong d-p orbital hybridization between V and Pb atoms, subsequently, N2 is activated to a larger extent. These interesting findings may provide a new path for designing active sites in SACs with excellent performance.

Simulations of Anisotropic Monolayer GaSCl for p-Type Sub-10 nm High-Performance and Low-Power FETs.

Two-dimensional materials have been extensively studied in field-effect transistors (FETs). However, the performance of p-type FETs has lagged behind that of n-type, which limits the development of complementary logical circuits. Here, we investigate the electronic properties and transport performance of anisotropic monolayer GaSCl for p-type FETs through first-principles calculations. The anisotropic electronic properties of monolayer GaSCl result in excellent device performance. The p-type GaSCl FETs with 10 nm channel length have an on-state current of 2351 µA/µm for high-performance (HP) devices along the y direction and an on-state current of 992 µA/µm with an on/off ratio exceeding 107 for low-power (LP) applications along the x direction. In addition, the delay-time (τ) and power dissipation product of GaSCl FETs can fully meet the International Technology Roadmap for Semiconductors standards for HP and LP applications. Our work illustrates that monolayer GaSCl is a competitive p-type channel for next-generation devices.

Modulation of Photocatalytic CO2 Reduction by n-p Codoping Engineering of Single-Atom Catalysts.

Transition metal (TM) single-atom catalysts (SACs) have been widely applied in photocatalytic CO2 reduction. In this work, n-p codoping engineering is introduced to account for the modulation of photocatalytic CO2 reduction on a two-dimensional (2D) bismuth-oxyhalide-based cathode by using first-principles calculation. n-p codoping is established via the Coulomb interactions between the negatively charged TM SACs and the positively charged Cl vacancy (VCl) in the dopant-defect pairs. Based on the formation energy of charged defects, neutral dopant-defect pairs for the Fe, Co, and Ni SACs (PTM0) and the -1e charge state of the Cu SAC-based pair (PCu-1) are stable. The electrostatic attraction of the n-p codoping strengthens the stability and solubility of TM SACs by neutralizing the oppositely charged VCl defect and TM dopant. The n-p codoping stabilizes the electron accumulation around the TM SACs. Accumulated electrons modify the d-orbital alignment and shift the d-band center toward the Fermi level, enhancing the reducing capacity of TM SACs based on the d-band theory. Besides the electrostatic attraction of the n-p codoping, the PCu-1 also accumulates additional electrons surrounding Cu SACs and forms a half-occupied dx2-y2 state, which further upshifts the d-band center and improves photocatalytic CO2 reduction. The metastability of Cl multivacancies limits the concentration of the n-p pairs with Cl multivacancies (PTM@nCl (n > 1)). Positively charged centers around the PTM@nCl (n > 1) hinders the CO2 reduction by shielding the charge transfer to the CO2 molecule.

Cu- and Fe-Doped Ni-Mn-Sn Shape Memory Alloys with Enhanced Mechanical and Magnetocaloric Properties.

Ni-Mn-Sn-based ferromagnetic shape memory alloys (FSMAs) are multifunctional materials that are promising for solid-state refrigeration applications based on the magnetocaloric effect (MCE) and elastocaloric effect (eCE). However, a combination of excellent multi-caloric properties, suitable operating temperatures, and mechanical properties cannot be well achieved in these materials, posing a challenge for their practical application. In this work, we systematically study the phase transformations and magnetic properties of Ni50-xMn38Sn12Cux (x = 0, 2, 3, 4, 5, and 6) and Ni50-yMn38Sn12Fey (y = 0, 1, 2, 3, 4, and 5) alloys, and the magnetic-structural phase diagrams of these alloy systems are reported. The influences of the fourth-element doping on the phase transitions and magnetic properties of the alloys are elucidated by first-principles calculations. This work demonstrates that the fourth-element doping of Ni-Mn-Sn-based FSMA is effective in developing multicaloric refrigerants for practical solid-state refrigeration.

Ultrahigh Potassium Storage Capacity of Ca2Si Monolayer with Orderly Multilayered Growth Mechanism.

As the rising renewable energy demands and lithium scarcity, developing high-capacity anode materials to improve the energy density of potassium-based batteries (PBBs) is increasingly crucial. In this work, a unique orderly multilayered growth (OMLG) mechanism on a 2D-Ca2Si monolayer is theoretically demonstrated for potassium storage by first-principles calculations. The global-energy-minimum Ca2Si monolayer is a semiconductor with isotropic mechanical properties and remarkable electrochemical properties, such as a low potassium ion migration energy barrier of 0.07 eV and a low open circuit voltage ranging from 0.224 to 0.003 V. Most notably, 2D-Ca2Si demonstrates an ultrahigh theoretical specific capacity of 5459 mAh g-1 and a total specific capacity of 610 mAh g-1, reaching up to 89% of the capacity of a potassium metal anode. Remarkably, the OMLG mechanism facilitates stable, dendrite-free deposition of hcp-K metal layers on the 2D-Ca2Si surface, where the ultrahigh and gradually converging lattice match as the layers increase is the key to achieving theoretically near-infinite growth. The study theoretically demonstrates the Ca2Si monolayer a highly promising anode material, and offers a novel potassium storage strategy for designing 2D anode materials with high specific capacity, rapid potassium-ion migration, and good safety.