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This paper investigated the impact of Co ions doping on the structure, magnetic properties, and magnetocaloric effect for La 0.8 Sr 0.2 Mn 1- x Co x O 3 ceramics (LSMCO) by sol-gel method and first-principles calculations The use of first-principles calculations was provided for subsequent experiments. The sol-gel preparation of LSMCO ceramics and sintered at 950 °C for 10 h. It was shown that the samples' cell volume and lattice constants changed slightly with increasing Co2+ doping but remained a rhombohedral structure (No.167, R-3c space group) by statistics of TEM and XRD. The average particle size for the LSMCO ceramics ranged from 130 nm to 170 nm. LSMCO's chemical composition was verified by EDS and XPS and it was demonstrated that Co2+ was successfully doped. The oxidation state of La was found to be +3, Mn is a mixture of Mn3+ and Mn4+ valence states, and Co is a mixture of Co3+ and Co2+ valence states using XPS. In the vicinity of Tc, all samples presented the second-order magnetic phase transition from ferromagnetic to paramagnetic resorting to normalization and the Banerjee criterion. The Tc dropped from 292 K to 237 K with increasing Co2+ doping. The blocking temperature and the saturation magnetization were suppressed by the Co2+ substitution while the maximum magnetic entropy change of the LSMCO ceramics was observed to reduce as Co2+ increased. When the external magnetic field is 5 T, the La 0.8 Sr 0.2 Mn 0.95 Co 0.05 O 3 ceramics has a Tc of 292 K and a maximum magnetic entropy change value of 3.47 J/(kg K). [ABSTRACT FROM AUTHOR]

Nowadays, Alkaline earth metal halofluoride, as part of layered materials, have drawn considerable interest for applications in optoelectronic devices and sensors, benefiting from wide bandgap properties. In this work, the monolayer alkaline earth metal halofluoride XYF (X = Ca/Sr/Ba, Y = Cl/Br/I) were investigated based on first-principles calculations. These monolayers can be exfoliated with energies comparable to conventional two-dimensional (2D) materials, suggesting their potential for practical applications. Additionally, XYF monolayers all exhibit excellent structural stability, with a maximum elastic modulus ranging from 37.144 to 76.829 N/m, indicating significant flexibility. More strikingly, these materials are characterized as ultra-wide bandgap (UWBG) semiconductors, with direct bandgaps spanning from 5.06 to 7.56 eV using HSE06 functional. Furthermore, exploration was conducted into introducing magnetism by doping of S and P atoms, thereby providing magnetic moments in non-magnetic systems. Our research broadens the spectrum of 2D wide-bandgap materials, and holds promise for their applications in optoelectronics, flexible electronics and spintronics. [ABSTRACT FROM AUTHOR]

Metal halide perovskites recently have emerged as a promising candidate for photodetection due to their exceptional photoelectric performance. However, the high dark current in these materials has hindered their practical application to imaging. In this study, a novel halogen‐mixed CsPbIBr2 microwire photodetector that has a remarkable reduction of dark current by over 100‐fold (compared to CsPbBr3), along with a substantial increase in photocurrent, which yields a significantly improved on/off ratio of 6.56 × 104, is developed. More importantly, the halogen‐mixed perovskite photodetector exhibits enhanced photodetection performance, including a high responsivity of 133 A W−1 and a remarkable specific detectivity of 4.02 × 1012 Jones even under ultraweak light conditions as low as 4.5 nW cm−2. More specifically, high‐resolution images are successfully obtained under ultraweak light conditions. The combined analysis of experimental results and first‐principles calculation attribute the excellent performance of the CsPbIBr₂ microwire photodetector to a significant reduction in dark current by suppressing ion migration and increasing carrier effective mass, and a remarkable increase in photocurrent resulting from reduced bandgap and enhanced light absorption, as compared to CsPbBr3. This research represents a significant advancement in the development of high‐performance 1D perovskite‐based photodetectors, with promising implications for ultra‐weak light imaging applications. [ABSTRACT FROM AUTHOR]

High-pressure effects can be used to effectively optimize the thermoelectric performance of wide-bandgap oxides. We build upon this finding to show that the synergistic effects of doping with aluminum and graphene composite give excellent thermoelectric performance under high pressure. By employing the parabolic band model, the Pisarenko curves are derived at different pressures, coupled with the band structure of Al-doped ZnO. An analysis indicates that pressure-induced narrowing of the bandgap in Al-doped ZnO reduces the electron excitation energy, thereby optimizing the electrical properties of the samples. The Debye Callaway model is also used to fit the lattice thermal conductivity of the samples, thus enabling an in-depth analysis of the phonon scattering mechanisms. Our analysis suggests that graphene composites significantly enhance point defect scattering and Umklapp scattering, thus increasing the phonon relaxation time and effectively reducing the lattice thermal conductivity of the samples. The improvement in the figure of merit (zT) of ZnO is attributed to the simultaneous enhancement of its electrical properties under high pressure and the synergistic optimization of reducing the lattice thermal conductivity through doping and composites. In this work, we consider a fixed doping ratio of Al and a constant proportion of graphene composite, and analyze the microstructure and thermoelectric properties of 0.1C–ZnAl 0.04 O (C–ZnAlO) samples synthesized under pressures ranging from 1 to 5 GPa, with the aim of elucidating the influence of pressure and graphene composite on the electro-acoustic transport properties of ZnO. We find that the zT value for a sample synthesized at 5 GPa is increased to 0.27 at 973 K. [ABSTRACT FROM AUTHOR]

Boron nitride has attracted scientific interest in recent years due to its potential use in electronics, both as hexagonal (hBN) and cubic (cBN) phases. While both are successfully realized through chemical vapor deposition, the heteroepitaxial growth of cBN on another iconic semiconductor, diamond is plagued with mixed‐phase formation. Employing first‐principles computations and a nanoreactor approach, the BN phase preferences are explored on diamond (001) controlled—as it is discovered—by the hydrogen gas concentration. In a limited‐hydrogen environment, the initial BN‐island expands along the diamond surface, forming a 3D metastable cubic phase that grows in the direction normal to the basal plane through kinetically‐limited nucleation, thus overcoming the thermodynamic preference toward the hBN phase. Comparatively, the amorphous phase is favored in the absence of hydrogen, while the hexagonal phase dominates at its high levels, elucidating numerous experimental observations. A obtained kinetic phase diagram connects the phase with hydrogen chemical potential to facilitate targeted phase selection. The results suggest that gas‐mediated nucleation kinetics provide feasible control for the precise synthesis. It also offers valuable guidance for the controllable synthesis of desired BN phases and advances research toward potential BN electronics. [ABSTRACT FROM AUTHOR]

2D carbon allotropes with moderated electronic bandgaps are highly desirable for next‐generation carbon‐based nanoelectronics beyond graphene. Herein, the structural and electronic properties of bilayer α‐graphyne have been systematically investigated by using first‐principles calculations. Consequently, in addition to typical van der Waals (vdW) stacks of single‐layer α‐graphyne, new 2D carbon allotropes with purely sp2 or sp3 hybridizations can be achieved, arising from the absence of intralayer acetylene linkages during structural relaxation. Compared to the Dirac semimetallic behavior of monolayer α‐graphyne, the electronic structure of vdW bilayer α‐graphyne can be further modulated by stacking patterns, yet retains metallic characteristics. In contrast, intrinsic semiconducting characteristics can be observed in the proposed new 2D carbon allotropes with tunable bandgaps dependent on the in‐plane biaxial strain. Correspondingly, a pristine 2D carbon sheet with only sp2 hybridization exhibits a promising direct bandgap of 1.062 eV, while the sp3‐hybridized carbon network possesses an indirect bandgap of 1.708 eV, which can be further converted to the direct type under small compressive strains, implying great potential in future carbon‐based nanoelectronic applications beyond graphene. Also, this work provides a new approach for developing novel carbon allotropes via the vertical stacking of graphyne with acetylenic linkages. [ABSTRACT FROM AUTHOR]

Revealing the hardening mechanisms is crucial for facilitating the design of superhard high‐entropy borides. Taking high‐entropy diborides (HEB2) as the prototype, the hardening mechanisms of high‐entropy borides are thoroughly investigated. Specifically, the equiatomic 4—9‐cation single‐phase HEB2 ceramics (4—9HEB2) are fabricated by an ultra‐fast high‐temperature sintering method. The experimental results show that the hardness of the as‐fabricated 4—9HEB2 samples has an increasing tendency with the increase of metal components. With a combination of first‐principles calculations, machine‐learning‐potential‐based molecular dynamics simulations, and scanning transmission electron microscopy characterizations, lattice distortion is explicitly identified to be essential in hardening HEB2 by increasing strain field fluctuation, enlarging atomic strain energy, and strengthening B─B bonds. The results unravel the hardening mechanisms of HEB2 by intensifying lattice distortion, providing fascinating guidance for developing superhard high‐entropy borides. [ABSTRACT FROM AUTHOR]

The development of high‐performance ion battery anode materials is conducive to the rapid development of urban rail transit. Based on first‐principles calculations, this paper studies the potential performance of the recently discovered two‐dimensional material SnSe2 as a negative electrode for zinc ion batteries. By calculating the adsorption energy, the most stable adsorption configuration of Zn was determined. The band gap of intrinsic SnSe2 decreases after strain, which promotes the transition of carriers. The band gap opens after the strain occurs in the Zn adsorbed SnSe2 system (Zn‐SnSe2), which confirms the regulation of strain on the band gap. The lowest diffusion barrier of Zn is 0.083 eV. The theoretical zinc storage capacity is calculated to be 387.550 mAh/g. The calculation results provide theoretical parameters for the application of SnSe2 in ion batteries. [ABSTRACT FROM AUTHOR]

There is great interest in developing advanced electrical conductors with higher conductivity, lighter weight, and higher mechanical strength than copper (Cu). One promising candidate is copper‐graphene (Cu‐Gr) composite, which is hypothesized to have a higher electrical conductivity than Cu. In this work, it is shown that this is not true, supported by state‐of‐the‐art first‐principles calculations of electron transport. Particularly, contrary to the belief that graphene in the composite is more conductive than pristine Cu, it is less conductive due to increased scattering despite increased carrier concentration. On the other hand, it is found that compressive strain along the (111) plane increases the conductivity, which is confirmed experimentally, while tensile strain has little effect. The work offers new insights into understanding and developing advanced conductors. [ABSTRACT FROM AUTHOR]

First-principles study is used to comparatively study the hydrogen embrittlement resistance, elastic properties, and electronic structures of VWH and VMoH phases with various W and Mo concentration. Calculations reveal that the VMo phases have lower hydrogen solubility compared to VW phases, leading to higher hydrogen embrittlement resistance in VMo. In addition, the concentrations of W and Mo above 0.1875 would enhance the hydrogen embrittlement resistance of V membrane. Conversely, the W or Mo concentrations below 0.1875 would reduce the hydrogen embrittlement resistance. It is also demonstrated that adding W and Mo at concentrations below 0.25 would reduce the solid-solution strengthening of VH phase, thereby reducing its brittleness. This study will enhance comprehension of the underlying physics of VWH and VMoH phases and align with existing experimental literature. • Adding Mo is more effective than adding W in improving the hydrogen embrittlement resistance of V membrane. • The concentrations of W or Mo above 0.1875 would enhance the hydrogen embrittlement resistance of V membrane. • The W or Mo concentrations below 0.1875 would reduce the hydrogen embrittlement resistance. • Adding W and Mo at concentrations below 0.25 would reduce its brittleness. [ABSTRACT FROM AUTHOR]

The exceptional synergy of ceramic and metallic properties within MAX phases positions them as highly promising for a wide array of applications. However, their stability has been threatened by the phenomenon of A-site metal whisker growth. Herein, we have significantly mitigated tin whisker growth in Ti 2 SnC by incorporating vanadium solutes at its M-site. With an increase in vanadium concentration, there is a marked reduction in the degree of decomposition of the M-site solid solution when subjected to the same level of externally destructive treatments, thereby inhibiting whisker proliferation. Both experimental outcomes and theoretical calculations reveal that the vanadium solid solution augments the hardness, Pugh's ratio, and Poisson's ratio of Ti 2 SnC, enhancing its mechanical strength and toughness. The incorporation of V atoms introduces stronger V–C and V–Sn bonds, as evidenced by its electronic density of states and bulk modulus, thus significantly bolstering the resistance of MAX phases against decomposition and effectively curtailing whisker growth. Additionally, the phenomenon reported in this paper also conforms to the electrostatic theory of whisker growth. This work for the first time achieves the suppression of A-site whisker growth through an M-site solid solution, thereby extending their potential for applications where durability and reliability are paramount. [ABSTRACT FROM AUTHOR]

For metal-free low-dimensional ferromagnetic materials, a hopeful candidate for next-generation spintronic devices, investigating their magnetic mechanisms and exploring effective ways to regulate their magnetic properties are crucial for advancing their applications. Our work systematically investigated the origin of magnetism of a graphitic carbon nitride (Pca21 C4N3) monolayer based on the analysis on the partial electronic density of states. The magnetic moment of the Pca21 C4N3 originates from the spin-split of the 2pz orbit from special carbon (C) atoms and 2p orbit from N atoms around the Fermi energy, which was caused by the lone pair electrons in nitrogen (N) atoms. Notably, the magnetic moment of the Pca21 C4N3 monolayer could be effectively adjusted by adsorbing nitric oxide (NO) or oxygen (O2) gas molecules. The single magnetic electron from the adsorbed NO pairs with the unpaired electron in the N atom from the substrate, forming a Nsub-Nad bond, which reduces the system's magnetic moment from 4.00 μB to 2.99 μB. Moreover, the NO adsorption decreases the both spin-down and spin-up bandgaps, causing an increase in photoelectrical response efficiency. As for the case of O2 physisorption, it greatly enhances the magnetic moment of the Pca21 C4N3 monolayer from 4.00 μB to 6.00 μB through ferromagnetic coupling. This method of gas adsorption for tuning magnetic moments is reversible, simple, and cost-effective. Our findings reveal the magnetic mechanism of Pca21 C4N3 and its tunable magnetic performance realized by chemisorbing or physisorbing magnetic gas molecules, providing crucial theoretical foundations for the development and utilization of low-dimensional magnetic materials. [ABSTRACT FROM AUTHOR]

Electronic properties of intrinsic ZnO, N‐doped ZnO, and Al–N‐codoped ZnO of both hexagonal wurtzite (HW) and zincblende (ZB) structures are investigated by first‐principles calculations. Both N‐doped ZB‐ZnO and N‐doped HW‐ZnO achieve p‐type transition by the introduction of N‐2p states, forming shallow acceptor levels above the valence band. However, the positive impurity formation energy implies the difficulty and instability of N‐doped ZnO. In Al–N‐codoped ZnO, the Al elements compensate the p‐type doping effect, but partially enhance the solubility of N. Furthermore, the comparison of the electronic properties between HW‐ZnO and ZB‐ZnO indicates that the ZB structure favors the achieving of p‐type doping. [ABSTRACT FROM AUTHOR]

Structural disorder is common in metal‐halide perovskites and important for understanding the functional properties of these materials. First‐principles methods can address structure variation on the atomistic scale, but they are often limited by the lack of structure‐sampling schemes required to characterize the disorder. Herein, structural disorder in the benchmark inorganic halide perovskites CsPbI3 and CsPbBr3 is computationally studied in terms of the three octahedral‐tilting angles. The subsequent variations in energetics and properties are described by 3D potential‐energy surfaces (PESs) and property landscapes, delivered by Bayesian optimization as implemented in the Bayesian optimization structure search code sampling density functional theory (DFT) calculations. The rapid convergence of the PES with about 200 DFT data points in 3D searches demonstrates the power of active learning and strategic sampling with Bayesian optimization. Further analysis indicates that disorder grows with increasing temperature and reveals that the material bandgap at finite temperatures is a statistical mean over disordered structures. [ABSTRACT FROM AUTHOR]

Gas sensors with the p–n heterojunction have demonstrated distinct sensing responses to reducing gases, yet a clear understanding of the reaction pathways and selective adsorption mechanisms for specific gas components remains elusive, impeding practical applications. In this study, we constructed an atomic-level NiO–In 2 O 3 heterojunction and explored its adsorption behaviors and sensing properties for CO and H 2 by first-principles calculations. Analysis of its electronic properties, focusing on binding energy, differential charge density, and density of states, confirmed the creation of a highly stable NiO–In 2 O 3 heterojunction and alterations in the coordination environment of the surface-active atoms. These changes potentially led to differences in the affinity between the gas molecules and the adsorption sites. The calculations of the adsorption properties revealed that the adsorption capacity of H 2 is relatively weak compared to the strong interactions between CO and heterojunction surface atoms, indicating a readily variable reaction pathway for H 2. Consequently, the adsorption configuration at the interface site on the NiO–In 2 O 3 heterojunction surface exhibited a predominantly p-type response for CO and a unique n-type response for H 2. This interfacial effect of the heterojunction is crucial for the selective adsorption of CO and H 2. Furthermore, the opposite response signal was verified by gas sensing tests, which also presented the superior stability of the NiO–In 2 O 3 sensor. The p–n heterojunction of the corresponding composites was effectively characterized. This research offers new insights into the selective adsorption mechanism, paving the way for the development of gas sensors. [ABSTRACT FROM AUTHOR]

The thermoelectric properties of monolayered MnBi2Te4 are investigated using first‐principles calculations based on density functional theory (DFT) and Boltzmann transport theory. Our research indicates significant thermoelectric performance in monolayered MnBi2Te4, with a maximum figure of merit (zT$zT$) and power factor (PF${\mathrm{PF}}$) ranging from approximately 3.58 to 9.267 and 0.012 W/K2m${\mathrm{W}}/{\mathrm{K}}^2{\mathrm{\ m}}$ to 0.021 W/K2m${\mathrm{W}}/{\mathrm{K}}^2{\mathrm{\ m}}$ across a temperature range of 300–700 K. The exceptional thermoelectric performance of monolayered MnBi2Te4 can be attributed to its unique structural and electronic properties, which lead to ultralow lattice thermal conductivity and high electrical transport properties. Ultralow lattice thermal conductivity as low as 0.32W/mK$0.32\ {\mathrm{W}}/{\mathrm{m\ K}}$ at 300 K is found in the monolayered MnBi2Te4, which is mainly contributed from the anharmonic scatterings of low‐frequency phonons. And high electronic conductivity and a notable Seebeck coefficient are also observed in our system, which has close relationship with its distinctive electronic band structure. Besides, the two‐dimensional structure makes it a great candidate to holding greater PF by enhancing the quantum confinement. Our findings may lay a strong theoretical groundwork for future experimental inquiries. Subsequent experimental investigations will be crucial to confirm these findings, refine synthesis methods, and explore the practical applications of monolayered MnBi2Te4 in thermoelectric devices. [ABSTRACT FROM AUTHOR]

This comprehensive review examines the structural, mechanical, electronic, and thermodynamic properties of Mg-Li-Al alloys, focusing on their corrosion resistance and mechanical performance enhancement. Utilizing first-principles calculations based on Density Functional Theory (DFT) and the quasi-harmonic approximation (QHA), the combined properties of the Mg-Li-Al phase are explored, revealing superior incompressibility, shear resistance, and stiffness compared to individual elements. The review highlights the brittleness of the alloy, supported by B/G ratios, Cauchy pressures, and Poisson's ratios. Electronic structure analysis shows metallic behavior with varied covalent bonding characteristics, while Mulliken population analysis emphasizes significant electron transfer within the alloy. This paper also studied thermodynamic properties, including Debye temperature, heat capacity, enthalpy, free energy, and entropy, which are precisely examined, highlighting the Mg-Li-Al phase sensitive to thermal conductivity and thermal performance potential. Phonon density of states (PHDOS) confirms dynamic stability, while anisotropic sound velocities reveal elastic anisotropies. This comprehensive review not only consolidates the current understanding of the Mg-Li-Al alloy's properties but also proposes innovative strategies for enhancing corrosion resistance. Among these strategies is the introduction of a corrosion barrier akin to the Mg-Li-Al network, which holds promise for advancing both the applications and performance of these alloys. This review serves as a crucial foundation for future research aimed at optimizing alloy design and processing methods. [ABSTRACT FROM AUTHOR]

The crystal structure, mechanical stability, phonon dispersion, electronic transport properties and thermoelectric (TE) performance of the Bi2Sn2Te6 monolayer are assessed with the first-principles calculations and the Boltzmann transport theory. The Bi2Sn2Te6 monolayer is an indirect semiconductor with a band gap of 0.91 eV using the Heyd-Scuseria-Ernzerhof (HSE06) functional in consideration of the spin-orbit coupling (SOC) effect. The Bi2Sn2Te6 monolayer is high thermodynamically and mechanically stable by the assessments of elastic modulus, phonon dispersion curves, and ab initio molecular dynamics (AIMD) simulations. The hybrid bonding characteristics are discovered in Bi2Sn2Te6 monolayer, which is advantageous for phonon scattering. The antibonding interactions near the Fermi level weaken the chemical bonding and reduce the phonon vibrational frequency. Due to the short phonon relaxation time, strong anharmonic scattering, large Grüneisen parameter, and small phonon group velocity, an ultralow lattice thermal conductivity (0.27 W/(m·K)@300K) is achieved for the Bi2Sn2Te6 monolayer. The optimal dimensionless figure of merit (ZT) values for the n-type and p-type Bi2Sn2Te6 monolayers are 2.68 and 1.63 at 700 K, respectively, associated with a high TE conversion efficiency of 20.01% at the same temperature. Therefore, the Bi2Sn2Te6 monolayer emerges as a promising candidate for TE material with high conversion efficiency. [ABSTRACT FROM AUTHOR]

The thermoelectric properties of monolayered MnBi2Te4 are investigated using first‐principles calculations based on density functional theory (DFT) and Boltzmann transport theory. Our research indicates significant thermoelectric performance in monolayered MnBi2Te4, with a maximum figure of merit (zT$zT$) and power factor (PF${\mathrm{PF}}$) ranging from approximately 3.58 to 9.267 and 0.012 W/K2m${\mathrm{W}}/{\mathrm{K}}^2{\mathrm{\ m}}$ to 0.021 W/K2m${\mathrm{W}}/{\mathrm{K}}^2{\mathrm{\ m}}$ across a temperature range of 300–700 K. The exceptional thermoelectric performance of monolayered MnBi2Te4 can be attributed to its unique structural and electronic properties, which lead to ultralow lattice thermal conductivity and high electrical transport properties. Ultralow lattice thermal conductivity as low as 0.32W/mK$0.32\ {\mathrm{W}}/{\mathrm{m\ K}}$ at 300 K is found in the monolayered MnBi2Te4, which is mainly contributed from the anharmonic scatterings of low‐frequency phonons. And high electronic conductivity and a notable Seebeck coefficient are also observed in our system, which has close relationship with its distinctive electronic band structure. Besides, the two‐dimensional structure makes it a great candidate to holding greater PF by enhancing the quantum confinement. Our findings may lay a strong theoretical groundwork for future experimental inquiries. Subsequent experimental investigations will be crucial to confirm these findings, refine synthesis methods, and explore the practical applications of monolayered MnBi2Te4 in thermoelectric devices. [ABSTRACT FROM AUTHOR]

The current study utilized DFT (density functional theory) calculations to examine the influence of Ca-doping on the optoelectronic properties of Ra0.875Ca0.125TiO3 (RCT12), Ra0.75Ca0.25TiO3 (RCT25), and Ra0.625Ca0.375TiO3 (RCT37). We utilize the FP-LAPW + lo (full potential linearized augmented plane wave plus local orbital) method in order to solve the Kohn–Sham equations using the generalized gradient approximation (GGA). The GGA model along with Hubbard potential (GGA + U) is utilized to compute fundamental properties of the studied perovskites. The energy bandgap values for RCT12, RCT25, and RCT37 are around 1.96, 1.92 and 1.87 eV, respectively. From the obtained ε 2 (ω) spectra, it is evident that RCT12, RCT25, and RCT37 compounds shows a substantial absorption of incoming photons in the visible and near UV region. The computed values of n (ω) for RCT12, RCT25, and RCT37 are 1.79, 1.77 and 1.76, respectively. The aforesaid compounds having n (ω) values in the range of 1.0 and 2.0 are regarded as active optical materials. The optoelectronic characteristics of RCT12, RCT25, and RCT37 suggest that they have promising potential for use in energy-related applications like solar cells. [ABSTRACT FROM AUTHOR]

The electronic and optical properties of RbPbBr3/RbPbBr2Cl, RbPbBr3/RbSnBr3 and RbSnBr3/RbSnBr2Cl heterostructures were studied using first-principle approach. The calculations show that the energy gaps are equal to 1.54, 0.96 and 0.67 eV (the energies are in the infrared range), respectively. Also, unlike the strong metallic property of RbSnBr3/RbSnBr2Cl, in the band structures of RbPbBr3/RbPbBr2Cl and RbPbBr3/RbSnBr3, the minimum of conduction bands is tangential to the Fermi level. Also, the density of states (DOS) diagrams around the Fermi level have negligible amplitude, so, the density of charge carriers is low and thereby both heterostructures (similar to graphene) can be suitable for electronic applications. The effective mass calculations show; me* & mh* < 0.5 me, therefore, in all three cases, charge carriers have significant mobilities and these structures are suitable for photovoltaic and optoelectronic applications. Also, partial density of states (PDOS) diagrams show that the charge carriers are concentrated in certain layers, therefore, in all three heterostructures, the two-dimensional electron gas is formed. By plotting the diagrams of changes in the length of the anion–cation–anion bond perpendicular to the junction, it can be seen that the ferroelectric-like property appears in these structures. The optical calculations show, for all cases, the refractive index in the range of (0.0–5.0 eV) has a value of about 1.6, with peaks as large as 1.87. In this range the reflectivity varies between 0.06 and 0.12. Finally, we found that the RbPbBr3/RbSnBr3 structure has two visible absorption peaks at 1.96 and 3.09 eV, while the heterostructures of RbPbBr3/RbPbBr2Cl and RbSnBr3/RbSnBr2Cl, each have one visible peak that are located at 2.78 and 2.11 eV respectively. [ABSTRACT FROM AUTHOR]

Developing economical non-platinum oxygen reduction reaction (ORR) catalysts is crucial for the continuous development of fuel cell technology. Transition metal phthalocyanines (TM-Pc) are recognized as ideal catalysts for ORR due to their high turnover frequency and structural tunability. However, the catalytic performance of TM-Pc monolayers with different central atom compositions in ORR has not been sufficiently investigated and explored so far. In this study, a series of TM-Pc monolayers with different central atom compositions were systematically screened to explore their interaction law and catalytic mechanism in ORR based on density functional theory, cleverly using a combination of high-throughput screening and experiment. Our calculations show that the change of the d-band center avoids the strong adsorption of intermediates, and the interaction strength between intermediates and TM-Pc determines the catalytic activities for the ORR. Among the 30 candidate materials, we identified two promising candidates, Fe-Pc and Mn-Pc, which not only have low overpotentials of 0.45 and 0.47 V but also have high thermodynamic and electrochemical stability. The results guide the rational design of high-performance ORR electrocatalysts and are also of reference significance for elucidating the catalytic mechanism of TM-Pc materials for ORR. [Display omitted] • TM-PC electrocatalysts for ORR are systematically screened. • Fe-Pc and Mn-Pc, two highly promising materials, are established. • The ORR mechanism of TM-Pc materials is thoroughly investigated. [ABSTRACT FROM AUTHOR]

Europium(III) (Eu3+/Eu(III)) substitution in the hydroxyapatite (HAp) lattice imparts luminescence properties, enabling its application in diagnostics and bioimaging. Despite numerous experimental studies, there has been a lack of comprehensive discussion on the substitution behavior and local structural stability of Eu3+ within HAp. In this study, experimental and first-principles investigations were integrated to explore and understand the substitution of Eu3+ in HAp. Optimization of various HAp models revealed the dependency of Eu3+ substitution site on the charge compensation mechanism. Eu3+ prefers the Ca(2) site when OH is converted to O and the Ca(1) site in the presence of a Ca vacancy. Phonon calculations showed that temperature influences charge compensation and site preference, favoring OH to O compensation and Eu3+ in Ca(2) at higher temperatures and Ca vacancy and Eu3+ in Ca(1) at lower temperatures. Electronic structure simulations explained that the luminescence in Eu(III)-substituted HAp primarily arises from charge transfer between Eu3+ and O atoms, supported by experimental photoluminescence measurements. Correspondence between simulations and experimental photoluminescence data emphasizes the reliability of the computational approach in this study. The integration of insights from experimental and simulation results enhances the understanding of substitution of Eu3+ in the HAp lattice, providing valuable guidance for designing and optimizing HAp-based luminescent and optical materials. [ABSTRACT FROM AUTHOR]

Finding a novel material to substitute the existing noble metal catalysts for the hydrogen evolution reaction (HER) is essential for the further advancement of water electrolysis technology. Herein, we investigated the feasibility of using defect engineering to improve the hydrogen evolution reaction (HER) catalytic performance of WTeX (X = Se, S) materials in the 2H, 1 T, and 1 T′ phases. The results demonstrate that the introduction of defects significantly enhances WTeX monolayers' HER performance. As exemplary cases, the Gibbs free energy changes for 2H WTeSe with a Te vacancy (2H WTeSe–V Te) and 2H WTeS with a Te vacancy (2H WTeS–V Te) are 0.029 eV and −0.002 eV, respectively. It was found that the active sites in 2H WTeSe–V Te and 2H WTeS–V Te have a substantial number of empty anti-bonding states, which increases the bond strength between H and the catalyst, leading to exceptional catalytic performance. This work demonstrates the feasibility of defect-engineered WTeX structures as electrocatalysts and provides a reliable reference for the study of non-precious metal catalysts. • Defect introduction boosts HER performance, especially in 2H WTeX-V Te. • W atoms' 5d orbitals play a key role in enhanced HER in 2H WTeX-V Te structures. • Strong W–H bonding forms stable H adsorption, promoting the HER process. • 2H phases show concentrated charge transfer, outperforming 1 T and 1 T′ in HER. [ABSTRACT FROM AUTHOR]

Modulating the electronic structure of transition metal dichalcogenides (TMDs) via alloying is challenging despite the additional potential applications. In this study, a solvothermal reaction is used to synthesize composition‐tuned ReS2–VS2 (Re1‐xVxS2) alloy nanosheets featuring an expanded interlayer distance. Increasing x induces a phase transition from the semiconducting 1T″ phase ReS2 to the metallic 3R‐stacking 1T phase VS2. Alloying via homogeneous atomic mixing renders the nanosheets more metallic and with less oxidation than VS2. First‐principles calculations consistently predict the 1T″–1T phase transition of the atomically mixed alloy structures. The calculation also suggests that intercalation drives the 3R stacking of 1T phase VS2. The Re1‐xVxS2 nanosheets at x = 0.3–0.8 exhibit enhanced electrocatalytic activity toward water‐splitting hydrogen evolution reaction (HER) in an acid electrolyte. In situ X‐ray absorption fine structure measurements reveal that the metallicity of the alloys is fully retained during HER. The density of states and Gibbs free energy calculations show that alloying increases the metallicity and thus effectively activates the basal S atoms toward the HER, supporting the observed increased HER performance of the alloy nanosheets. [ABSTRACT FROM AUTHOR]

2D materials have attracted considerable attention in the past decades for their unique properties, making the understanding of their nucleation process key to effective synthesis. Traditional explanations of thin‐film growth, focusing on the competition between atom interactions at the interface and within layers, often fall short of explaining real experimental results. Herein, a penetrated nucleation mechanism is proposed for 2D materials growth on metal substrates, taking into account the role of metal substrate atoms. This approach leads to a better understanding of how the surface shape evolves in two specific ways during growth in real experimental findings. Supported by detailed first‐principles simulations of boron on metal substrates and thermodynamic analyses of other studies involving metals and nonmetals, the above‐proposed mechanism is validated. Moreover, a broad strategy for growing large‐scale 2D materials on metal surfaces without creating undesired alloy layers is also presented, by adjusting the interfacial interactions by surface passivation, validated by existing experiments. [ABSTRACT FROM AUTHOR]

Context: The adsorptions of gas (CO, CO2, NH3) by metal (Au, Ag, Cu)-doped single layer WS2 are studied by density functional theory. The doping of metal atoms makes WS2 behave as n-type semiconductors. The final adsorption sites for CO, CO2, and NH3 are close to the atomic sites of the doped metal. The adsorptions of CO and NH3 gases on Cu/WS2, Ag/WS2, and Au/WS2 are dominated by chemisorption. The doped metal atoms enhance the hybridization of the substrate with the gas molecular orbitals, which contributes to the charge transfer and enhances the adsorption of the gas with the material surface. The adsorptions of CO and NH3 on Cu/WS2 and Ag/WS2 allow favorable desorption in a short time after heating. The single-layer Cu/WS2 is proved to have the potential to be used as a reliable recyclable sensor for CO. This work provides a theoretical basis for developing high-performance WS2-based gas sensors. Methods: In this paper, the adsorption energy, electronic structure, charge transfer, and recovery time of CO, CO2, and NH3 in the doped system have been investigated based on the CASTEP code of density functional theory. The exchange correlation function used is the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The TS (Tkatchenko-Scheffler) dispersion correction method was used to involve the effects of van der Waals interaction on the adsorption energies for all adsorption system. The ultrasoft pseudopotentials are chosen and the plane-wave cut-off energies are set to 500 eV. The k-point mesh generated by the Monkhorst package scheme is used to perform the numerical integration of the Brillouin zone and 5 × 5 × 1 k-point grid is used. The tolerances of total energy convergence, maximum ionic force, ionic displacement, and stress component are 1.0 × 10−5 eV/atom, 0.03 eV/Å, 0.001 Å, and 0.05 GPa, respectively. [ABSTRACT FROM AUTHOR]

The method of linearized full-potential augmented plane waves based on density functional theory (DFT) is employed to investigate the structural, elastic, magnetic electronic, and thermoelectric properties of the cerium-based half-Heusler alloy FeCeSi. The exchange correlation functional is treated with the generalized gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE) and the Tran-Blaha-modified Beck-Johnson (TB-mBJ) as implemented in the Wien2k package. According to our results, we have discovered that the material studied is mechanically stable, which means that this compound can be synthesized experimentally. Furthermore, FeCeSi exhibits a half-metallic behavior obeying the Slater-Pauling rule with an integer magnetic moment of 2 μB. The electronic band structures and density of states confirm the half-metallic character with an indirect band gap equals to 0.51 eV and 0.59 eV for GGA-PBE and TB-mBJ approximation, respectively. For the study of the thermoelectric parameters, such as Seebeck coefficient (S), electrical conductivity (σ), thermal conductivity (κ), and figure of merit (ZT), the Boltzmann transport equations within the framework of DFT have been used. Significant values for the figure of merit and Seebeck coefficient indicate promising candidate for useful thermoelectric applications for FeCeSi alloy. So far, no experimental or theoretical investigations have been carried out on the half-Heusler alloy FeCeSi. Accordingly, our theoretical results concerning structural, elastic, electronic, magnetic, and thermoelectric properties will probably be confirmed by experimental investigations. [ABSTRACT FROM AUTHOR]

The results of first-principles calculations of the structural, electronic, elastic, vibrational, dielectric and optical properties, as well as the Raman and infrared (IR) spectra, of potassium hexafluorosilicate (K2SiF6; KSF) crystal are discussed. KSF doped with manganese atoms (KSF:Mn4+) is known for its ability to function as a phosphor in white LED applications due to the efficient red emission from Mn⁴⁺ activator ions. The simulations were performed using the CRYSTAL23 computer code within the linear combination of atomic orbitals (LCAO) approximation of the density functional theory (DFT). For the study of KSF, we have applied and compared several DFT functionals (with emphasis on hybrid functionals) in combination with Gaussian-type basis sets. In order to determine the optimal combination for computation, two types of basis sets and four different functionals (three advanced hybrid—B3LYP, B1WC, and PBE0—and one LDA functional) were used, and the obtained results were compared with available experimental data. For the selected basis set and functional, the above-mentioned properties of KSF were calculated. In particular, the B1WC functional provides us with a band gap of 9.73 eV. The dependencies of structural, electronic and elastic parameters, as well as the Debye temperature, on external pressure (0–20 GPa) were also evaluated and compared with previous calculations. A comprehensive analysis of vibrational properties was performed for the first time, and the influence of isotopic substitution on the vibrational frequencies was analyzed. IR and Raman spectra were simulated, and the calculated Raman spectrum is in excellent agreement with the experimental one. [ABSTRACT FROM AUTHOR]

AlB2${\rm AlB}_{2}$‐type TaB2${\rm TaB}_{2}$ is one of the transition‐metal diborides, a class of refractory ceramics, that has increasingly received attention due particularly to their potential for hard‐coating applications. In this work, the first‐principles calculations are performed, in combination with the cluster‐expansion method, to investigate the effect of mixing AlB2${\rm AlB}_{2}$ with TaB2${\rm TaB}_{2}$ on the thermodynamic stability, structural parameters, electronic density of states, and mechanical behavior of the resulting (Ta,Al)B2${\rm B}_{2}$ solid solutions. It is found that the solid solutions display the chemical ordering of Ta and Al atoms both residing on the metal sublattice of the material, together with the preference for partial substitution of vacancies for Al atoms. This results in the formation of Al‐deficient (Ta,Al)B2${\rm B}_{2}$ with the chemical composition Ta0.6Al0.3B2${\rm Ta}_{0.6} {\rm Al}_{0.3} {\rm B}_{2}$, predicted to be thermodynamically stable even at absolute zero in the ternary Ta−Al−B system. It is further found that such formation of Al vacancies in (Ta,Al)B2${\rm B}_{2}$ not only enhances the stability of the solutions but also improves their elastic properties and hardness, both of which could be attributed to the effect of electronic band filling. This investigation indeed sheds light on the interplay between the mixing of Ta and Al atoms and the presence of Al vacancies on the alloying and mechanical behaviors of (Ta,Al)B2${\rm B}_{2}$, and it thus offers valuable insights for further research and development of these ceramics. [ABSTRACT FROM AUTHOR]

The vacancies and nitrogen dopants significantly alter the interfacial bonding and electrical properties at the graphene/metal interface. The graphene/copper system, characterized by coherent and immiscible interfaces, serves as a suitable benchmark to elucidate the intrinsic interactions between carbon and metal atoms. Herein, the individual effects of vacancies and nitrogen dopants, as well as their combined effects, are systematically investigated. The bonding energies show that the interfacial bonding is the strongest at the monovacancy (MV) graphene/copper interface, indicating that the introduction of nitrogen in defective graphene/copper interfaces weakens the interfacial bonding. Furthermore, the band structures indicate that both vacancies and nitrogen dopants contribute to the formation of a bandgap. Among them, both MV and graphitic nitrogen doping significantly enhance interfacial bonding while maintaining relatively intact interfacial and band structures. [ABSTRACT FROM AUTHOR]

The development of next‐generation 6G communications is anticipated to expand into extreme environments, necessitating superior terahertz (THz) electromagnetic interference (EMI) shielding materials. Herein, structural stability, electronic and optical properties of rare earth silicide carbide Yb3Si2C2 are investigated using first principles density functional calculations and semi‐classical Boltzmann transport theory. The calculation results show Yb3Si2C2 is determined to be experimentally synthesized with high temperature stability with a certain fluctuating C2 pair orientation. In addition, Yb3Si2C2 is identified as a soft, tough, and damage‐resistant ceramic with low shear deformation resistance and easy cleavage, ensuring its durability in irradiation environments. Due to the layered structure and excellent electrical conductivity, Yb3Si2C2 demonstrates high reflectivity and low transmittance for terahertz electromagnetic waves, along with 62% solar absorptivity and 33% IR emissivity. Remarkably, the total shielding effectiveness of Yb3Si2C2 with thicknesses of 5 µm and above follows the widely‐used Simon's formula. The average total shielding effectiveness of 5 µm‐thick and 10 µm‐thick Yb3Si2C2 across the entire THz region reaches 63 and 110 dB, respectively, which turns out to be the top compared to the results reported. Therefore, the multifunctional intrinsic properties of Yb3Si2C2 materials hold great promise for miniaturized, high‐performance terahertz EMI shielding, even in extreme environments. [ABSTRACT FROM AUTHOR]

The precipitation process of inclusions in the high sulfur steel with the cerium addition is observed using the high‐temperature confocal scanning laser microscope (CSLM). Rare earth (Re) inclusions formed in the molten steel, and MnS inclusions precipitate along grain boundaries or on oxide cores at the end of solidification. With the addition of cerium, the average aspect ratio of inclusions in the steel decreases from 6.5 to 5.0, and the addition of cerium effectively modifies the elongated MnS. Thermodynamic calculations show the inclusion transformation during solidification, yet it lacked the formation of Ce2O2S and Re sulfides. According to the first‐principles calculation, the priority of the inclusion formation was Ce2O3 > CeAlO3, Ce2O2S > CeS > Ce3S4 > MnS. The stability of MnS inclusions is much lower than that of cerium‐containing inclusions. It is in situ observed that the addition of cerium promotes the formation of cerium‐containing inclusions and reduces the precipitation of MnS in the high sulfur steel. [ABSTRACT FROM AUTHOR]

Based on the first-principles calculations of density functional theory,we have investigated the modulation of the electronic properties of bilayer pent-graphene by hydrogenation,fluorination and hydrofluorination.The calculated results show that hydrogenated and fluorinated bilayer penta-graphene can form localized electronic states at the bottom of the conduction band and the top of the valence band,respectively,and significantly reduce the band gap. Based on the unique properties,we further investigate the hydrofluorinated bilayer penta-graphene to modulate the band gap. Consequently,we propose a facile approach for effectively tuning the band gap via modulating the coverage of hydrofluorination and hence realizing the semiconductor-to-metal transition of bilayer penta-graphene. [ABSTRACT FROM AUTHOR]

Context: The adsorptions of gas (CO, CO2, NH3) by metal (Au, Ag, Cu)-doped single layer WS2 are studied by density functional theory. The doping of metal atoms makes WS2 behave as n-type semiconductors. The final adsorption sites for CO, CO2, and NH3 are close to the atomic sites of the doped metal. The adsorptions of CO and NH3 gases on Cu/WS2, Ag/WS2, and Au/WS2 are dominated by chemisorption. The doped metal atoms enhance the hybridization of the substrate with the gas molecular orbitals, which contributes to the charge transfer and enhances the adsorption of the gas with the material surface. The adsorptions of CO and NH3 on Cu/WS2 and Ag/WS2 allow favorable desorption in a short time after heating. The single-layer Cu/WS2 is proved to have the potential to be used as a reliable recyclable sensor for CO. This work provides a theoretical basis for developing high-performance WS2-based gas sensors. Methods: In this paper, the adsorption energy, electronic structure, charge transfer, and recovery time of CO, CO2, and NH3 in the doped system have been investigated based on the CASTEP code of density functional theory. The exchange correlation function used is the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The TS (Tkatchenko-Scheffler) dispersion correction method was used to involve the effects of van der Waals interaction on the adsorption energies for all adsorption system. The ultrasoft pseudopotentials are chosen and the plane-wave cut-off energies are set to 500 eV. The k-point mesh generated by the Monkhorst package scheme is used to perform the numerical integration of the Brillouin zone and 5 × 5 × 1 k-point grid is used. The tolerances of total energy convergence, maximum ionic force, ionic displacement, and stress component are 1.0 × 10−5 eV/atom, 0.03 eV/Å, 0.001 Å, and 0.05 GPa, respectively. [ABSTRACT FROM AUTHOR]

The full-potential linearized augmented plane wave plus local orbital method is utilized for exploring the electronic, magnetic, and magneto-optical properties of the NiX2 (X=Cl, Br, and I) single layer. The first-principles calculation demonstrates that these compounds are ferromagnetic indirect semiconductors, and the energy band gaps of NiX2 for X=Cl, Br, and I are 3.888, 3.134, and 2.157 eV, respectively. The magnetic moments of Ni atoms in NiX2 monolayer are 1.656, 1.588, 1.449 µB, and their magneto-crystalline anisotropy energies are 0.167, 0.029, 0.090 meV, respectively. Based on the macro-linear response theory, we systematically studied the influences of the external magnetic field and out-of-plane strain on the magneto-optical Kerr effect (MOKE) spectrum of the NiX2 single layer. It is found that, when the external magnetic field is perpendicular to the sample plane, the value of the Kerr rotation angle reaches the maximum, and the single-layer NiI2 material has a Kerr rotation angle of 1.89° at the photon energy of 1.986 eV. Besides, the Kerr rotation spectrum of NiCl2 and NiBr2 monolayers redshift as the out-of-plane strain increases, while NiI2 monolayer blueshifts. Accurate computation of the MOKE spectrum of NiX2 materials provides an opportunity for applications of 2D magnetic material ranging from sensing to data storing. [ABSTRACT FROM AUTHOR]

Inorganic lead-free metal halide perovskites are being rigorously explored as a substitute for organic lead-based materials for various energy device applications. Germanium as a replacement for lead has been proven to give exemplary results theoretically, and there have been promising results. The current work presents the investigation of CsGeI3 (CGI) polycrystals grown using a solution-free melt-growth technique with low-cost precursors. A soak-ramp profile was designed to synthesize polycrystalline powders, which were evaluated for stability. X-ray diffraction and Raman spectroscopy analysis suggest the formation of CsGeI3 perovskite powders, matching the reported literature. Diffuse reflectance spectroscopy measurements showed the bandgap of the polycrystals to be around 1.6 eV. A prominent photoluminescence peak was obtained at 767 nm. The powders were examined using thermogravimetric analysis to assess the thermal degradation pathways. The as-grown inorganic perovskite polycrystals were relatively stable during storage under ambient conditions. Theoretical studies were also carried out to support the experimental data. Calculations were performed with different approximations, including local density approximation (LDA), generalized gradient approximation (GGA), and Heyd–Scuseria–Ernzerhof (HSE) approximation, out of which the HSE approximation yielded the most accurate results that matched the experimental findings. Moreover, for the CGI device with Ag electrodes simulated using SCAPS-1D software, highest incident photon-to-electron conversion efficiency was observed. The obtained optical and structural properties indicate the suitability of the synthesized CsGeI3 perovskite polycrystals for photovoltaic applications, specifically solar cells and light-emitting diodes. [ABSTRACT FROM AUTHOR]

In this study, La0.63Sr0.2Nd0.17MnO3 was synthesized by the sol-gel method, and its structural, morphological, magnetic, and magnetocaloric effects were investigated. The structural properties were analyzed by x-ray diffraction (XRD), and scanning electron microscopy (SEM) was used to characterize the morphology. An integrated magnetic measurement system was used to determine the magnetic properties. La0.63Sr0.2Nd0.17MnO3 crystallized in a hexagonal crystal system with space group R-3c. This was also confirmed by Rietveld refinement of the x-ray data from La0.63Sr0.2Nd0.17MnO3. With the doping of Nd3+, the cell volume decreases, which can be explained by the angles and bond lengths of the bonds between the Mn and O ions and the distortion of the lattice. Near the Curie temperature, La0.63Sr0.2Nd0.17MnO3 exhibits significant magnetocaloric effects. The magnetic study of La0.63Sr0.2Nd0.17MnO3 suggests that the transition from the paramagnetic to ferromagnetic phase can occur near the Curie temperature. The maximum magnetic entropy change and relative cooling power (RCP) of La0.63Sr0.2Nd0.17MnO3 (298 K, 3 T) are 2.70 J/(kg K) and 135 (J/kg), respectively. The effect of f-orbitals on the magnetic properties of La0.8Sr0.2MnO3 was investigated by first-principles calculations in density functional theory. Thus, it can be concluded that the magnetocaloric effects of the material after doping with f-orbital ions (Nd3+) is enhanced compared to La0.8Sr0.2MnO3. [ABSTRACT FROM AUTHOR]

Tungsten (W) and tungsten alloys are being considered as leading candidates for structural and functional materials in future fusion energy devices. The most attractive properties of tungsten for the design of magnetic and inertial fusion energy reactors are its high melting point, high thermal conductivity, low sputtering yield, and low long-term disposal radioactive footprint. Despite these relevant features, there is a lack of understanding of how the structural and mechanical properties of W-based alloys are affected by the temperature in fusion power plants. In this work, we present a study on the thermo-mechanical properties of five W-based plasma-facing materials. First-principles density functional theory (DFT) calculations are combined with the quasi-harmonic approximation (QHA) theory to investigate the electronic, structural, mechanical, and thermal properties of these W-based alloys as a function of temperature. The coefficient of thermal expansion, temperature-dependent elastic constants, and several elastic parameters, including bulk and Young's modulus, are calculated. Our work advances the understanding of the structural and thermo-mechanical behavior of W-based materials, thus providing insights into the design and selection of candidate plasma-facing materials in fusion energy devices. [ABSTRACT FROM AUTHOR]

In recent years, significant advancements have been made in the fabrication and application of graphene-reinforced metal matrix composites. The remarkable mechanical properties of graphene have led to a substantial enhancement in the strength of titanium-based composites reinforced with graphene nanosheets. However, the occurrence of severe interfacial reactions remains one of the most challenging issues in graphene-reinforced titanium matrix composites. This study, grounded in first principles, investigates the interfacial bonding between pure titanium and graphene across two distinct crystal structures, as well as the impact of vacancy defects on the composite's interfacial structure. The bond strength between beta titanium and graphene is found to be relatively weaker, which may facilitate a reduction in the reactivity between graphene and titanium. Furthermore, the presence of vacancy defects is identified as a crucial factor influencing the formation of titanium carbide. This study presents a novel approach to enhance the interfacial adhesion between graphene and titanium. [ABSTRACT FROM AUTHOR]

First-principles calculations are performed, revealing a significant enhancement of the piezoelectric properties of wurtzite Zn 3 6 O 3 6 upon the incorporation of a single Cu atom. Research has demonstrated that the piezoelectric constant d 3 3 reaches its maximum value at a doping concentration of 1.4% for Cu atoms. The lattice parameters a and c of Zn 3 6 O 3 6 are decreased and the piezoelectric strain coefficient d 3 3 is increased by replacing one Cu atom in Zn 3 6 O 3 6 . It is found that elastic softening is the primary factor responsible for the increase of d 3 3 in Zn 3 5 Cu1O 3 6 . By differential charge density analysis, it is found that the covalency between Cu–O bonds is lower than that of Zn–O bonds, and the covalent bonding characteristics are weakened. Bader charge analysis shows that the charge of Cu is higher than that of Zn, indicating a more significant ionic bonding feature than that of Zn. Thus, a weaker covalent and stronger ionic bond are considered to play an essential role in promoting elastic softening for ZnO, which eventually promotes a significant enhancement in piezoelectric properties. [ABSTRACT FROM AUTHOR]

Incorporating atomically thin 2D semiconductors (2DSCs) into the vertical complementary field‐effect transistors (CFETs) is of great significance in enabling devices to break through the sub‐nanometer scaling limit. However, due to the lack of effective doping technology and the difficult‐to‐control electrode interface, simultaneously realizing high‐performance p‐type and n‐type devices using a single metal electrode presents great challenges for 2D‐CFETs design. In this study, an innovative electrical contact strategy is proposed by constructing van der Waals heterojunction (vdWH) using 2DSCs to regulate the electrical contact properties between the metal electrode and 2DSC channel. First‐principles calculations reveal that degenerate or quasi‐degenerate complementary doping is achieved in a series of transition metal dichalcogenides (TMDs) by designing (quasi‐)broken‐gap vdWHs and utilizing their interlayer charge transfer. Metal‐2DSC contact barriers can be effectively regulated by introducing 2DSC intercalation and constructing vdWH. P‐type (quasi‐)Ohmic contacts are realized between Au electrode and various TMD channels, as well as between WTe2 channel and different metal electrodes. Moreover, quantum transport simulations present the remarkable on‐current over 102 µA µm−1 in both p‐type and n‐type 2D‐FETs by employing the vdWH and metal‐vdWH electrodes. The proposed vdWH strategy is applicable to various metal‐2DSC contacts and will shed light on future high‐performance 2D‐CFET integrations. [ABSTRACT FROM AUTHOR]

The structural, electronic, elastic, optical, phonon, and thermo-physical properties of the tetragonal X 2 CoH 5 (X = Ca, Sr) hydrogen storage compounds were thoroughly examined using first-principles calculations. The negative formation enthalpies (−76.03 kJ/mol.H 2 for Ca 2 CoH 5 and −72.55 kJ/mol.H 2 for Sr 2 CoH 5) highlight the structural stability of these materials. Phonon calculations revealed no imaginary frequency modes, confirming the dynamic stability of X 2 CoH 5. The mechanical stability of Ca 2 CoH 5 and Sr 2 CoH 5 was evidenced by the compliance of the elastic constants with Born stability criteria. The electronic band structure indicates that Ca 2 CoH 5 and Sr 2 CoH 5 are direct bandgap semiconductors with narrow bandgaps of ∼ 0.27 and 0.34 eV, respectively. The appraisal of Poisson's ratio (ν = 0.22 for X = Ca and 0.23 for Sr) and Pugh's ratio (B/G = 1.47 for X = Ca and 1.56 for Sr) suggests that both metal hydrides exhibit brittle mechanical behavior. Moreover, 3D plots of Young's modulus (E), shear modulus (G), linear compressibility (β), and Poisson's ratio (ν) uncover anisotropy within X 2 CoH 5. The hydrogen storage capabilities were scrutinized, and the present materials feature excellent volumetric hydrogen density (95.65 gH 2 l −1 for Ca 2 CoH 5 and 80.24 gH 2 l −1 for Sr 2 CoH 5), moderate gravimetric hydrogen density (3.38 wt% for Ca 2 CoH 5 and 2.06 wt% for Sr 2 CoH 5) and high hydrogen desorption temperature (584 K for Ca 2 CoH 5 and 558 K for Sr 2 CoH 5). Notably, the obtained volumetric hydrogen densities are in line with the volumetric capacity criteria set by the U.S. Department of Energy (DOE) for 2025. Finally, the optical and thermo-physical characteristics of X 2 CoH 5 compounds were also investigated in this work. • New X 2 CoH 5 (X = Ca and Sr) hydrides were studied using first-principles calculations. • The X 2 CoH 5 compounds are thermodynamically, dynamically and mechanically stable. • X 2 CoH 5 hydrides display semiconductor behavior, brittleness, and elastic anisotropy. • The Gravimetric capacity was calculated as 3.38 wt% for Ca 2 CoH 5 2.06 wt% for Sr 2 CoH 5. [ABSTRACT FROM AUTHOR]

The electronic and photocatalytic properties of a type-II ZnS/HfS 2 heterojunction are comprehensively analyzed through first-principles calculations in this paper. By calculating the binding energy and phonon spectrum of five potential stacking patterns, the stable structure of the ZnS/HfS 2 heterojunction is determined. The electronic structure calculations indicate that the heterojunction has a type-II alignment with a 1.26 eV band gap. The heterojunction exhibits high carrier mobilities (4387.36 and 9561.39 cm2V–1S−1 for X and Y directions). The photocatalytic water splitting process of the heterojunction can be explained by the direct Z-scheme mechanism. The built-in electric field enables rapid recombination of electron-hole pairs at CBM and VBM, while the hydrogen evolution reaction and oxygen evolution reaction can separately be achieved at the ZnS layer and HfS 2 layer to complete the overall water splitting. The free energy analysis indicates that the ZnS/HfS 2 heterojunction has high activity for overall water splitting under illumination. Moreover, the calculated solar-to-hydrogen efficiency of the heterojunction reaches 30%, ensuring its photocatalytic performance. Remarkably, the type-II alignment is maintained and the catalytic performance can be further improved under biaxial strain because of the enhanced optical absorption in visible light and the reduced band gap. This work reveals that ZnS/HfS 2 heterojunction is a potentially novel photocatalytic material for efficient overall water splitting. [Display omitted] • Proposed novel type-II ZnS/HfS 2 heterojunction with 1.26 eV band gap. • Achieves overall water splitting via direct Z-scheme mechanism. • High carrier mobility and 30% solar-to-hydrogen efficiency. • Enhanced catalytic performance under biaxial strain. [ABSTRACT FROM AUTHOR]

Nanotwin strengthening mechanism has been successfully applied to a variety of metallic materials. The strengthening originates from the hindering effect of twin-boundary (TB) on dislocations, and the formation of twin is greatly determined by the magnitude of the TB energy (TBE). In this work, the TBEs of three face-centered-cubic (FCC) metals were calculated by first-principles, the effect of the supercell size (the TB spacing and TB area) on the TBE was investigated, and the relationship between the TBE and the twinning formation mechanism was discussed. The results show that the TBEs calculated in this paper are in good agreement with the experimental values. Meanwhile, the magnitude of the TBE explains reasonably the twinning formation ability of these FCC metals in experiments. [ABSTRACT FROM AUTHOR]

Iron‐nitrogen functionalized graphene has emerged as a promising cathode host for rechargeable lithium‐sulfur batteries (RLSBs) due to its affordability and enhanced battery performance. To optimize its catalytical efficiency, we propose a novel approach involving coordination engineering. Our investigation spans a plethora of catalysts with varied coordination environments, focusing on elements B, C, N and O. We revealed that Fe−C4 and Fe−B2C2−h are particularly effective for promoting Li2S oxidation, whereas Fe‐N4 excels in catalyzing the sulfur reduction reaction (SRR). Importantly, our study identified specific descriptors – namely, the Integrated Crystal Orbital Hamilton Population (ICOHP) and the bond length between Fe and S in Li2S adsorbed state – as the most effective predictive descriptors for Li2S oxidation barriers. Meanwhile, Li2S adsorption energy emerges as a reliable descriptor for assessing the SRR barrier. These identified descriptors are expected to be instrumental in rapidly identifying promising cathode hosts across various metal‐centered systems with diverse coordination environments. Our findings not only offer valuable insights into the role of coordination environment, but also present an effective path for rapidly identifying high performance catalysts for RLSBs, enabling the acceleration of advanced RLSBs development. [ABSTRACT FROM AUTHOR]

Perovskite-type structures have unique crystal architecture and chemical composition, which make them highly attractive for the design of solar cells. For instance, perovskite-based solar cells have been shown to perform better than silicon cells, capable of adsorbing a wide range of light wavelengths, and they can be relatively easily manufactured at a low cost. Importantly, the perovskite-based structures can also adsorb a significant amount of hydrogen atoms into their own structure; therefore, perovskite holds promise in the solid-state storage of hydrogen. It is widely expected by the scientific community that the controlled adsorption/desorption of the hydrogen atoms into/from perovskite-based structures can help to overcome the main hydrogen storage issues such as a low volumetric density and the safety concerns (i.e., the hydrogen embrittlement affects strongly the mechanical properties of metals and, as such, the storage or transport of the gaseous hydrogen in the vessels is, especially for large vessel volumes, challenging). The purpose of this review is to provide an updated overview of the recent results and studies focusing on the perovskite materials used for both solar cells and hydrogen storage applications. Particular attention is given to (i) the preparation and the achievable efficiency and stability of the perovskite solar cells and (ii) the structural, thermodynamic, and storage properties of perovskite hydrides and oxides. We show that the perovskite materials can not only reach the efficiency above current Si-based solar cells but also, due to good stability and reasonable price, can be preferable in the solid-state storage of hydrogen. Then, the future trends and directions in the research and application of perovskite in both solar cells and hydrogen storage are also highlighted. [ABSTRACT FROM AUTHOR]

Air pollution and greenhouse emissions are significant problems across various sectors, urging the need for advanced technologies to detect and capture harmful gases. In recent years, two‐dimensional (2D) materials have attracted increasing attention due to their large surface‐to‐volume ratio and reactivity. Herein, we investigate the potential of single‐layer CrSBr for gas sensing and capturing by means of first‐principles calculations. We explore the adsorption behaviour of different pollutant gases (H2S, NH3, NO, NO2, CO and CO2) on this 2D ferromagnet and the impact of intrinsic defects on its magnetic properties. Interestingly, we find that Br vacancies enhance the adsorption of NH3, NO and NO2 and induce a selective frequency shift on the magnon dispersion. This work motivates the creation of novel magnonic gas sensing devices based on 2D van der Waals magnetic materials. [ABSTRACT FROM AUTHOR]

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

Although Al–H hydrides are promising hydrogen storage materials due to the high hydrogen storage capacity and low density, the structural stability, electronic and optical properties of H-rich region AlH x are entirely unknown. To explore the hydrogen storage material with high hydrogen storage capacity, here, we apply the first-principle method to study the structural stability, hydrogen storage capacity, electronic and optical properties of three AlH x (x = 4, 5 and 6) hydrides. The calculated results show that three AlH x hydrides are thermodynamic stability due to the negative formation enthalpy. In particular, it is found that the calculated hydrogen storage capacity (C wt.%) is 11.44 wt% for AlH 4 , 13.52 wt% for AlH 5 and 15.39 wt% for AlH 6 , respectively. Compared to MgH 2 (7.66 wt%), the hydrogen storage capacity of AlH 4 , AlH 5 and AlH 6 increases by about 49.3%, 76.5% and 100.9%. Naturally, the [AlH 3 ] group and [AlH 5 ] group in AlH 5 , the [AlH 6 ] group in AlH 4 and AlH 6 are beneficial to store a lot of hydrogen. In addition, the calculated band gap of AlH 4 , AlH 5 and AlH 6 is 3.08 eV, 3.11 eV and 4.27 eV, respectively. The semiconductor properties of three AlH x hydride is demonstrated by the dielectric functional. Finally, it is found that three AlH x hydrides show ultraviolet properties. [Display omitted] • Three H-rich region AlH x dihydrides are thermodynamic stability. • The hydrogen storage capacity(C wt.%) of AlH 4 , AlH 5 and AlH 6 is 11.44 wt%, 13.52 wt% and 15.39 wt%. • Compared to MgH 2 , the C wt.% of AlH 4 , AlH 5 and AlH 6 increases by about 49.3%, 76.5% and 100.9%. • The higher hydrogen storage capacity of AlH x relies on the product of [AlH 4 ], [AlH 5 ] and [AlH 6 ] group. • Three AlH x dihydrides exhibit semiconductor properties. [ABSTRACT FROM AUTHOR]