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Hydrogen energy plays an important role in achieving green and low-carbon transformation and development. It is a feasible method to produce clean hydrogen by solar irradiation. In this paper, a new type of InN/BTe van der Waals heterojunction is designed based on density functional theory. The calculated results show that the lattice mismatch of the heterojunction is less than 2% and has good stability, which is beneficial to the experimental synthesis. Under light irradiation, the transfer path of electrons and holes generated by light excitation is Z-scheme mechanism, which accumulates in BTe conduction band and InN valence band with stronger redox activity, respectively, and improves the efficiency of photocatalytic hydrolysis. The InN/BTe heterojunction under the standard hydrogen electrode can achieve complete decomposition of water and spontaneous hydrogen evolution reaction. The high solar-to-hydrogen conversion efficiency (up to 17.92%) and electron mobility (1820.54 cm2/Vs) indicate that the InN/BTe heterojunction is a promising photocatalytic material. [Display omitted] • The design of a novel direct Z-scheme InN/BTe heterojunction. • The HER of InN/BTe heterojunction occurs spontaneously under the standard hydrogen electrode. • The solar-to-hydrogen conversion efficiency of InN/BTe heterojunction is as high as 17.92%. • InN/BTe heterojunction is a potential efficient photocatalyst. [ABSTRACT FROM AUTHOR]

To solve the shuttling effect and transformations of LiPSs in lithium–sulfur batteries, heterostructures have been designed to immobilize LiPSs and boost their reversible conversions. In this paper, we have constructed AlN/InN heterojunctions with AlN with a wide band gap and InN with a narrow band gap. The heterojunctions show metallic properties, which are primarily composed of 2s, 2p N atoms and 5s, 5p In atoms. InN has relatively higher adsorptivity for LiPSs than AlN. Reaction profiles show that on the surface of AlN, there is a lower rate-limiting step than on that of InN, from S8 to Li2S6, and a higher rate-limiting step from Li2S4 to Li2S2, which is more favorable for InN during the reduction from Li2S4 to Li2S2. The heterojunction can realize the synergistic reaction of trapping–diffusion–conversion for LiPSs, in which AlN traps large Li2S8 and Li2S6, the heterojunction causes the diffusion of Li2S4, and InN completes the conversion of Li2S4 to Li2S. [ABSTRACT FROM AUTHOR]

Ussingite (Na2AlSi3O8OH) is a mineral with a unique interrupted framework structure and strong hydrogen bonding. It contains 4-, 6-, and 8-membered tetrahedral rings resembling feldspars, but, unlike the latter, is partially depolymerized. There are four crystallographically distinct tetrahedral (T) sites, two of which (T1, T2) are Q4 [i.e., having 4 next nearest neighbor (NNN) T sites], and the other two (T3, T4) are Q3 (i.e., having 3 NNN T sites), each with NNN (in brackets) of T1(1T2, 1T3, 2T4), T2(1T1, 2T3, 1T4), T3(1T1, 2T2), and T4(2T1, 1T2). There is one unique OH site in the T4-O8-H···O2-T3 configuration, where O8 and O2 are nonbridging O atoms (NBO). In the ordered structure, T1 is fully occupied by Al, and the other three T sites by Si. Previous X-ray and neutron diffraction and 1H and 29Si NMR studies gave contradictory conclusions regarding Si-Al disorder. In this study, we were able to unambiguously clarify the issue via comprehensive one- and two-dimensional 1H, 29Si, 27Al, and 23Na NMR and first-principles calculation. It was revealed that there is ~3% Si-Al disorder that occurs between neighboring T1-(O)-T2 sites, such that the formation of Al-O-Al linkage and Al(Q3) are avoided. The disorder was found to result in the development of Si(Q3) sites with various NNN, including 3Al and 3Si, and neighboring OH sites having significantly shorter and longer hydrogen-bonding distances than in the ordered structure, with 1H chemical shifts near 15~16 ppm and 11 ppm, in addition to a main peak near 13.9 ppm. Good correlation was found between 1H chemical shift, hydrogen-bonding (O-H, H···O, and O···O) distances, and Si-O distances in the Si-O-H···O-Si linkage. This suggests that Si-Al disorder is correlated with variation in hydrogen-bonding distances via through-bond transmission of bond valence variations. This could be a universal phenomenon also applicable to other hydrous minerals. The revelation of preferential partition of Al in Q4 over Q3 sites to avoid the formation of Al-OH and Al-NBO provides insight into their behavior in other partially depolymerized hydrous aluminosilicate systems, such as glasses and melts. [ABSTRACT FROM AUTHOR]

Vapor catalysis was recently found to play a crucial role in superclean graphene growth via chemical vapor decomposition (CVD). However, knowledge of vapor-phase catalysis is scarce, and several fundamental issues, including vapor compositions and their impact on graphene growth, are ambiguous. Here, by combining density functional theory (DFT) calculations, an ideal gas model, and a designed experiment, we found that the vapor was mainly composed of Cui clusters with tens of atoms. The vapor pressure was estimated to be ∼ 10−12–10−11 bar under normal low-pressure CVD system (LPCVD) conditions for graphene growth, and the exposed surface area of Cui clusters in the vapor was 22–269 times that of the Cu substrate surface, highlighting the importance of vapor catalysis. DFT calculations show Cu clusters, represented by Cu17, have strong capabilities for adsorption, dehydrogenation, and decomposition of hydrocarbons. They exhibit an adsorption lifetime and reaction flux six orders of magnitude higher than those on the Cu surface, thus providing a sufficient supply of active C atoms for rapid graphene growth and improving the surface cleanliness of the synthesized graphene. Further experimental validation showed that increasing the amount of Cu vapor improved the as-synthesized graphene growth rate and surface cleanliness. This study provides a comprehensive understanding of vapor catalysis and the fundamental basis of vapor control for superclean graphene rapid growth. [ABSTRACT FROM AUTHOR]

Good environmental compatibility and excellent insulation performance make trifluoroiodomethane (CF3I) have the potential to replace SF6 in gas-insulated equipment. The gas–solid compatibility of CF3I, its main decomposed products (I2, C2F6, C3F8, C2F4, HF, CF3H, COF2), and environmental molecule H2O with the Al and Cu(111) surfaces is investigated based on first-principles calculations. The most stable adsorption configurations of Al and Cu(111) surfaces adsorbed by all gas molecules are constructed, and the interaction types between gas molecules and two metal surfaces are determined by adsorption energy (E ad), charge transfer, and charge density difference. The absolute E ad of CF3I and I2 adsorbed on Al(111) surfaces are 4.09 and 3.76 eV, respectively. In contrast, the absolute E ad of other gases adsorbed on Al(111) surfaces do not exceed 0.99 eV, indicating that CF3I and I2 have strong chemical interactions and poor gas–solid compatibility with Al(111) surfaces, while other gases exhibit good gas–solid compatibility with the Al surface. The absolute E ad of I2 (1.15 eV) adsorbed on Cu(111) surface is significantly larger than that of other gases-adsorbed systems (not exceeding 0.99 eV) including CF3I-adsorbed system, proving that the gas–solid compatibility of I2 with Cu(111) surfaces is worse than that of other gases. In addition, the reasons for the different compatibility of CF3I with Al and Cu(111) surfaces are analyzed in depth through the density of states. [ABSTRACT FROM AUTHOR]

Due to their properties and potential applications, two-dimensional (2D) materials have shown enormous advantages in electronic and piezoelectric devices. Unfortunately, few 2D materials have both higher piezoelectric effects and better mechanical durability. We predict the Janus γ-GeSnXO (X = S, Se) monolayer with practicable piezoelectric property and good mechanical durability based on density functional theory. The dynamic, thermodynamic, and mechanical stability results can prove it. In addition, the piezoelectric coefficient d33 is 1 to 2 orders of magnitude higher than that of the same type of piezoelectric material. The calculation results meet the law of the electronegativity difference ratio. The piezoelectric performance increases with the increase of the electronegativity difference ratio. Furthermore, there is an intrinsic coupling mechanism between piezoelectric and electronic transport properties in this work, where a smaller polarization electric field is accompanied by a larger carrier mobility. This research establishes a practical foundation to address the requirements of diverse piezoelectric nanodevices. [ABSTRACT FROM AUTHOR]

Extensive research has been conducted on silver niobite (AgNbO 3)-based antiferroelectric ceramics for their promising applications in energy storage applications, with various compositional modifications explored to improve their energy storage capabilities. In this theoretical study, we have systematically investigated the electronic, structural, and chemical bonding properties of AgNb 1- x Ta x O 3 (x = 0.00, 0.125, 0.25, 0.375, 0.50, abbreviated as ANT100 x) solid solutions based on first-principles calculation. Our results reveal that the bandgap increases from 1.82 eV to 1.89 eV, due to the higher energy level of Ta 5 d orbitals compared to Nb 4 d orbitals. The enlarged bandgap, accompanied with oxygen vacancy formation energy (Δ E f , v a c ), contributes to the enhancement of E b. The Ta substitution of Nb site suppresses the cation displacement, oxygen octahedral distortion, and bond length and angles, indicating an improved stability of antiferroelectric phase. In addition, the electron localization function (ELF) and Bader charge values show weakened covalent bonding of Ta−O bonds compared to Nb−O bonds. These theoretical findings have the potential to aid in the advancement and creation of novel energy storage applications using lead-free AFE perovskites, as well as facilitate the manipulation of their breakdown electric field through bandgap engineering. [ABSTRACT FROM AUTHOR]

Partially occupied orbitals play a pivotal role in enhancing the performance of electrocatalyst by facilitating electron acceptance and donation, thus enabling the activation of molecular bonds. According to this principle, the basal plane of most 2D semiconductors is inert for electrocatalysis because of the fully occupied orbitals at the surface. Here, taking monolayer CrX (X = P, As, Sb) and Cr2PY (Y = As, Sb) as examples and through first‐principles calculations, it is revealed that even with fully occupied surface orbitals, the basal planes exhibit remarkable catalytic activity for the nitrogen oxide reduction reaction (NORR). This leads to the concept of the pseudo‐inert electrocatalyst. The underlying physics behind such pseudo‐inert character can be attributed to the reversal‐activation mechanism: contrary to conventional expectations, the adsorbed NO molecule reversely triggers the activity of the inert basal plane first, and then the basal plane activates NO molecules, forming the intriguing "Reversal Activation‐Transfer‐Donation‐Backdonation" process. This study further predicts that such pseudo‐inert character can demonstrate many distinctive properties, for example, it can introduce a novel type of surface catalysis, one that selectively targets radicals possessing an inherent dipole moment such as NO. The explored phenomena and insights greatly enrich the realms of electrocatalysis and 2D materials. [ABSTRACT FROM AUTHOR]

Pb plays an important role in determining the morphologies and mechanical properties of the Mg2Si phase in Mg-2.5Si-xPb alloys. As the amount of Pb increases from 0.4 wt.% to 1 wt.%, the primary Mg2Si phase is refined during solidification. Its morphologies transform from equiaxed-dendrite to polygonal and finally to roughly circular. The key reason for morphology evolution is the preferential adsorption of Pb atoms on Mg2Si {100} surfaces to suppress the growth rate along the ⟨100⟩ directions, which is demonstrated by the adsorption model based on first principles. In addition, the hardness of the Mg2Si phase decreases with the increasing solution content of Pb according to the results of the nanoindentation. With the addition of Pb at 1 wt.%, Pb content in the primary Mg2Si phase reaches a maximum of 0.4 wt.%, and the hardness of the primary Mg2Si phase reaches a minimum of 3.64 GPa. This reduction in hardness is attributed to the augmented ionic bond ratio resulting from the solution of Pb, which concurrently enhances the toughness of the Mg2Si phase. [ABSTRACT FROM AUTHOR]

The solid electrolyte Li10GeP2S12 (LGPS) plays a crucial role in the development of all-solid-state batteries and has been widely studied both experimentally and theoretically. The properties of solid electrolytes, such as thermodynamic stability, conductivity, band gap, and more, are closely related to their ground-state structures. However, the presence of site-disordered co-occupancy of Ge/P and defective fractional occupancy of lithium ions results in an exceptionally large number of possible atomic configurations (structures). Currently, the electrostatic energy criterion is widely used to screen favorable candidates and reduce computational costs in first-principles calculations. In this study, we employ the machine learning- and active-learning-based LAsou method, in combination with first-principles calculations, to efficiently predict the most stable configuration of LGPS as reported in the literature. Then, we investigate the diffusion properties of Li ions within the temperature range of 500–900 K using ab initio molecular dynamics. The results demonstrate that the atomic configurations with different skeletons and Li ion distributions significantly affect the Li ions' diffusion. Moreover, the results also suggest that the LAsou method is valuable for refining experimental crystal structures, accelerating theoretical calculations, and facilitating the design of new solid electrolyte materials in the future. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials with a high solar to hydrogen (STH) conversion are in high demand due to the escalating energy crisis and environmental degradation. The STH efficiency is strongly correlated with the charge carrier separation, which can be improved by the inside electric dipole. Herein, the water-splitting capabilities of single-layer (SL) GaInS 3 are explored by employing first-principles calculations. Theoretical outcomes reveal that SL GaInS 3 exhibits a large intrinsic electric dipole and has a thermally stable structure at 300 K. SL GaInS 3 displays a direct bandgap of 1.83 eV, as well as suitable band edges and abundant visible absorption (105 cm−1) for solar-driven water-splitting. The electronic structure and carrier mobility calculations demonstrate the high separation efficiency of charge carriers, which is strongly affirmed by the quite long carrier lifetime of 8.26 ns. The overpotential analysis of charge carriers suggests that the oxygen generation of SL GaInS 3 can be accomplished without a cocatalyst, while hydrogen generation can be completed with the aid of cocatalysts. The STH efficiency of SL GaInS 3 reaches up to 16.8%, apparently surpassing the commercial standard (10%). In brief, the high STH and long carrier lifetime promise the possible application of SL GaInS 3 for solar water splitting. What's more, this work provides straight evidence that 2D photocatalysts with inside dipoles exhibit a long carrier lifetime. • Single-layer GaInS 3 has appropriate and edges and abundant visible absorption for solar water-splitting. • The electronic structure confirms the high charge carrier separation efficiency in single-layer GaInS 3. • The quite long carrier lifetime of 8.26 ns in single-layer GaInS 3 is predicted. • The solar to hydrogen conversion of single-layer GaInS 3 reaches up to 16.8%. [ABSTRACT FROM AUTHOR]

The rational design of an electrocatalyst with excellent catalytic activity and high stability is at the core of large-scale hydrogen production from water splitting. As a fascinating, innovative class of effective electrocatalysts for hydrogen evolution reaction (HER), two-dimensional (2D) pentagonal noble metal sulfide MX 2 (M = Pd, Pt; X = S, Se, Te) have emerged as promising materials, but they are still suffering from the intrinsic activity for practical applications. The catalytic performance of the catalyst was adjusted by optimizing the electronic configuration of the catalyst and introducing Janus asymmetry and defect engineering. Here, we successful designed and demonstrated 2D defect Janus pentagonal noble metal sulfide materials (defect penta-MXY; M = Pd, Pt; X,Y S, Se, Te (X≠Y)). The results show that the catalytic performance was significantly improved after the introduction of defects and Janus, with the best hydrogen adsorption Gibbs free energy (from |ΔG H* |>1eV of penta-MX 2 to |ΔG H* |<0.2 eV of defect penta-MXY), and has excellent exchange current density (−16.96 A cm2). Interestingly, among the six catalysts, penta-PtSSe-V Se , penta-PdSSe-V Se , penta-PtSTe-V Te and penta-PtSeTe-V Te have higher work functions (∼5.52 eV), which promote the Volmer reaction step of HER at lower overpotentials (The energy barrier of penta-PtSSe-V Se 1 is only 1.01 eV). Moreover, we further revealed that the penta-MXY-V Y 1 materials exhibit excellent thermal and electrochemical stability, and the reasons for the improvement of electrocatalytic activity were investigated by studying the charge density difference, Bader charges, crystal orbital Hamilton population and d-band center (The penta-PtSSe-V Se 1 is −0.15 eV). The procedure followed in this work may be extended to the Janus pentagonal materials, thus expanding their potential application fields. • First-principles study of hydrogen evolution reaction. • Introducing Janus Asymmetry and Defect Engineering in Penta-MX 2. • The higher work function of penta-MXY promoted the hydrogen evolution reaction. • The Gibbs free energy of penta-PtSSe-VSe is as low as 0.02 eV. [ABSTRACT FROM AUTHOR]

In order to search for good hydrogen storage materials, the structural, optoelectronic and hydrogen storage properties of double perovskites KNaMg 2 F 6-x H x and KNaAe 2 H 6 (Ae = Be, Mg, Ca) have been studied by first-principles calculations based on density functional theory in this paper. All the negative formation energies demonstrate the thermodynamic stability of these materials. Except for KNaBe 2 H 6 , the rest of the materials are wide-band gap semiconductors or insulators. The gravimetric storage capacity of KNaMg 2 F 6-x H x increases with the introduction of hydrogen and reaches a maximum of 5.19 wt% at x = 6. Meanwhile, the KNaBe 2 H 6 exhibits the best storage capacity of 8.57%. The favorable desorption temperature for stable KNaMg 2 H 6 material is 470.4 K, which is feasible in actual application. As the concentration of hydrogen increases, the electronic bandgap of KNaMg 2 F 6-x H x decreases gradually due to its electron conduction band moving to a lower energy range. The bond population analysis indicates that there is a mixture of ionic and covalent bonds in the studied materials. These materials are all ultraviolet absorber, and a red-shift can be observed in the absorption edge due to the variation of bandgap. • Double perovskites are introduced as the novel hydrogen storage materials. • Hydrogen substitution improves the stability and optoelectronic performance of double perovskites. • All materials exhibit wide band gaps as well as high ultraviolet absorption. • Stable KNaMg 2 H 6 material possesses ideal desorption temperature of 470.4 K and gravimetric storage capacity of 5.19 wt%. [ABSTRACT FROM AUTHOR]

We performed 1H and 29Si NMR and infrared measurements, and first-principles calculations to clarify the nature of OH defects in MgSiO3 orthoenstatite. An orthoenstatite sample synthesized at 7 GPa and 1200 °C from a composition of MgSiO3 + 0.1 wt% H2O yielded two 1H MAS NMR peaks near 5.9 and 7.6 ppm that are correlated in 2D NMR spectra, and two infrared bands near 3361 and 3066 cm− 1 that correspond to the previously reported A3 and A4 bands. The first-principles calculations confirmed that they are due to a pair of protons in a Mg (M2) vacancy. The previously reported A1 and A2 infrared bands near 3687 and 3592 cm− 1 for orthoenstatite synthesized at low silica activities were confirmed to arise from four protons in a SiB vacancy. The latter is predicted to give two additional OH stretching bands associated with two strongly hydrogen-bonded O3b-H bonds with frequencies below the spectral range reported thus far. The previously reported infrared absorption coefficients were thus revised to account for the undetected bands. 1H NMR may be used to quantitatively detect all four protons (expected at 1–12 ppm). Other mantle minerals should also be examined for potentially overlooked OH defects with strong hydrogen bonding. [ABSTRACT FROM AUTHOR]

Lead-free (Ba 0.85 Ca 0.15)(Ti 0.90 Zr 0.10)O 3 (BCZT)-based piezoelectric ceramics have attracted considerable interest due to their excellent piezoelectric properties and abundant phase structures. However, there is a serious lack in the theoretical calculations for the ferroelectric phase transition behavior. Here, the experimental and first-principles calculations were utilized to analyze the ferroelectric phase transition process of (Ba 0.85 Ca 0.15)(Ti 0.90 Zr 0.10)O 3 - x Gd 2 O 3 (BCZT- x Gd, x = 0, 0.02, 0.04, and 0.05) ceramics. The incorporation of Gd 2 O 3 has induced a transformation from tetragonal to rhombohedral phase due to the decrease in the dislocation energy with A-site cations and the attenuation of the bonding energy between B-site cations and the planar O atoms. Moreover, the hybridization between the d orbitals of B-site atoms and the O 2p orbitals, coupled with the reduction of the polarization vector along the [001] axis, leads to enhanced weak coupling relaxation. This work provides a theoretical basis for the ferroelectric phase transition behavior of other piezoelectric systems. [ABSTRACT FROM AUTHOR]

MAlSiN3:Eu2+ (M = Ca, Sr) is commonly used in high‐power phosphor‐converted white‐light‐emitting diodes and laser diodes to promote their color‐rendering index. However, the wide application of this phosphor is limited by the degradation of its luminescent properties in high‐temperature, high‐humidity, and high‐sulfur‐content environment. Here, the degradation mechanism of the (Sr,Ca)AlSiN3:Eu2+ (SCASN) red phosphor under thermal‐moisture‐sulfur coupling conditions is investigated. Furthermore, by performing first‐principles calculations, the hydrolysis mechanism on an atomic scale is assessed. The adsorption energy (Eads) and charge transfer (ΔQ) results showed that H2O chemically adsorbed on the (0 1 0), (3 1 0), and (0 0 1) surfaces of the CaAlSiN3 (CASN) host lattice. The energy barrier for H2O dissociation is only 29.73 kJ mol−1 on the CASN (0 1 0) surface, indicating a high dissociation probability. The formation of NH3, Ca(OH)2, and CaAl2Si2O8 is confirmed by H+ tended to combine with surface N atoms, while OH− combined with the surface Al/Si or Ca atoms. Moreover, ab initio molecular dynamics simulations were performed to further understand the hydrolysis process. This work offers a guidance on the design and applications of luminescent materials in LED packages with higher reliability and stability requirements in harsh environment. [ABSTRACT FROM AUTHOR]

In this paper, using CsMA2Sn2I7 as an example, first‐principles calculations are performed to thoroughly investigate the crystal structures, electronic properties, and optical properties of 11 representative anchoring group/low‐dimensional hybrid perovskite systems. The results show that the addition of benzene, 4‐iodoaniline, aniline, and benzenethiol anchoring groups causes a blueshift phenomenon in the absorption spectra of CsMA2Sn2I7 perovskite. Furthermore, the involvement of the benzoic acid anchoring group has a minimal effect on the absorption spectra of the CsMA2Sn2I7 hybrid perovskites, which show better absorption intensity only in the ultraviolet. The addition of other anchoring groups leads to varying degrees of redshift in the absorption spectra of CsMA2Sn2I7 perovskite, which not only enhances absorption intensity but also lends to the improvement of the absorption efficiency in the visible range. In addition, the bandgap can be tuned by applying biaxial strain, which further effectively modulates the absorption intensity of the adsorption systems in different optical bands. Therefore, the selection of suitable anchoring groups has great potential for modulating the photovoltaic performance of organic–inorganic hybrid perovskites, which is helpful for the application of organic–inorganic perovskites in photovoltaics. [ABSTRACT FROM AUTHOR]

In the quest to enhance the mechanical properties of CuP alloys, particularly focusing on the Cu3P phase, this study introduces a comprehensive investigation into the effects of various alloying elements on the alloy's performance. In this paper, the first principle of density universal function theory and the projection-enhanced wave method under VASP 5.4.4 software are used to recalculate the lattice constants, evaluate the lattice stability, and explore the mechanical properties of selected doped elements such as In, Si, V, Al, Bi, Nb, Sc, Ta, Ti, Y and Zr, including shear, stiffness, compression, and plasticity. The investigation reveals that strategic doping with In and Si significantly enhances shear resistance and stiffness, while V addition notably augments compressive resistance. Furthermore, incorporating Al, Bi, Nb, Sc, Ta, Ti, V, Y, and Zr has substantially improved plasticity, indicating a broad spectrum of mechanical enhancement through precise alloying. Crucially, the validation of our computational models is demonstrated through hardness experiments on Si and Sn-doped specimens, corroborating the theoretical predictions. Additionally, a meticulous analysis of the states' density further confirms our computational approach's accuracy and reliability. This study highlights the potential of targeted alloying to tailor the mechanical properties of Cu3P alloys and establishes a robust theoretical framework for predicting the effects of doping in metallic alloys. The findings presented herein offer valuable insights and a novel perspective on material design and optimization, marking a significant stride toward developing advanced materials with customized mechanical properties. [ABSTRACT FROM AUTHOR]

MAX phases have great research value and application prospects, but it is challenging to synthesize the MAX phases containing Cd and Sb for the time being. In this paper, we confirmed the existence of the 312 MAX phases of Zr3CdC2 and Zr3SbC2, both from theoretical calculations and experimental synthesis. The Zr3AC2 (A = Cd, Sb) phase was predicted by the first-principles calculations, and the two MAX phases were confirmed to meet the requests of thermal, thermodynamic, and mechanical stabilities using formation energy, phonon dispersion, and the Born–Huang criteria. Their theoretical mechanical properties were also systematically investigated. It was found that the elastic moduli of Zr3CdC2 and Zr3SbC2 were 162.8 GPa and 164.3 GPa, respectively. Then, differences in the mechanical properties of Zr3AC2 (A = Cd, In, Sn, and Sb) were explained using bond layouts and charge transfers. The low theoretical Vickers hardness of the Zr3CdC2 (5.4 GPa) and Zr3SbC2 (4.3 GPa) phases exhibited excellent machinability. Subsequently, through spark plasma sintering, composites containing Zr3CdC2 and Zr3SbC2 phases were successfully synthesized at the temperatures of 850 °C and 1300 °C, respectively. The optimal molar ratio of Zr:Cd/Sb:C was determined as 3:1.5:1.5. SEM and the EDS results analysis confirmed the typical layered microstructure of Zr3CdC2 and Zr3SbC2 grains. [ABSTRACT FROM AUTHOR]

This study aims to foster students' computational thinking by integrating research project-based teaching methods. It outlines a comprehensive series of computational experiments centered on the first-principles calculations of the LiFePO4 cathode material, a prominent subject of study in lithium-ion battery research. The designed computational experiments encompass modeling of crystal structures, structure optimizations, electronic structure calculations, lithium-ion diffusion estimations, and post-experiment analyses. This approach ensures students gain a profound understanding of the foundational principles, processes, and analytical methods of first-principles calculations. Simultaneously, it bolsters both their grasp of theoretical methods and proficiency in software operations. [ABSTRACT FROM AUTHOR]

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Van der Waals (vdW) heterostructures provide an effective strategy for exploring and expanding the potential applications of two-dimensional materials. In this study, we employ first-principles density functional theory (DFT) to investigate the geometric, electronic, and optical properties of MoGe2N4/AlN and MoSiGeN4/AlN vdW heterostructures. The stable MoGe2N4/AlN heterostructure exhibits an indirect band gap semiconductor with a type-I band gap arrangement, making it suitable for optoelectronic devices. Conversely, the stable MoSiGeN4/AlN heterostructure demonstrates various band gap arrangements depending on stacking modes, rendering it suitable for photocatalysis applications. Additionally, we analyze the effects of mechanical strain and vertical electric field on the electronic properties of these heterostructures. Our results indicate that both mechanical strain and vertical electric field can adjust the band gap. Notably, application of an electric field or mechanical strain leads to the transformation of the MoGe2N4/AlN heterostructure from a type-I to a type-II band alignment and from an indirect to a direct band transfer, while MoSiGeN4/AlN can transition from a type-II to a type-I band alignment. Type-II band alignment is considered a feasible scheme for photocatalysis, photocells, and photovoltaics. The discovery of these characteristics suggests that MoGe2N4/AlN and MoSiGeN4/AlN vdW heterostructures, despite their high lattice mismatch, hold promise as tunable optoelectronic materials with excellent performance in optoelectronic devices and photocatalysis. [ABSTRACT FROM AUTHOR]

Twist bilayer graphene (tBLG) with a small magic angle deviated from trivial stacking exhibits fantastic electronic properties. However, the growth of large‐area tBLG with precisely controlled twist angle remains a grand challenge due to the thermodynamically unfavorable nucleation. Here, a bi‐oriented step‐guided strategy is theoretically proposed for the nucleation and epitaxial growth of tBLG, where the twist angle can be predetermined by the orientations of adjacent steps owing to the covalent alignment between the steps and graphene zigzag edges. The presence of bi‐oriented steps can greatly reduce the free energy of the tBLG with matched twist angle, thus promoting the nucleation priority of tBLG. Importantly, it is shown that the 28 sets of bi‐oriented steps with twist angles of 1.5°–30° can be intentionally constructed via two‐step miscutting from bulk crystal of catalytic metals by exploring all potential combinations of bi‐steps on different epitaxial surfaces. The employment of either low‐temperature CVD growth with certain precursors or the high‐melting‐point metal substrates is suggested to against the reconstruction of bi‐oriented steps during growth. This work demonstrates an efficient scheme for the epitaxial growth of large‐area tBLG with pre‐designed twist angle, which can be potentially extended to the growth of other twist 2D materials. [ABSTRACT FROM AUTHOR]

SnSe compound (Nature , 2014 , 508 , 373–377) has become the star in the field of thermoelectric (TE) materials owing to the environmental friendliness, abundant reserves, and excellent performance. In the present work, the electronic structures, thermal and electronic transport, as well as TE properties of a two-dimensional (2D) wrinkled SnSe monolayer are comprehensively investigated in combination with first-principles calculations and Boltzmann transport theory. The SnSe monolayer is an indirect semiconductor with a bandgap of 2.88 eV using Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional. The "multivalley" band structure of SnSe monolayer is not only beneficial for maximizing the power factor, but also leads to low lattice thermal conductivity (κ l) (1.37/1.42 W/mK @ 300 K armchair-/zigzag-direction). The further crystal orbital Hamilton population (COHP) analysis shows that the low κ l in SnSe monolayer is attributed to weak antibonding state below the Fermi level, which in turn weakens the chemical bonding and leads to the mutual exclusion of Sn and Se atoms. As a consequence, the softening of phonon modes and a significant reduction in the phonon group velocity are discovered for the SnSe monolayer, which is beneficial for strong anharmonicity and significant phonon scatterings. Additionally, the electronic transport properties of the 2D SnSe monolayer are evaluated by taking into account the electron-phonon interactions, and the optimal ZT s of 2.13 (armchair-direction) and 3.01 (zigzag-direction) are achieved for n -type and p -type SnSe monolayer at 900 K, respectively. Our present work can not only provide fundamental understanding of thermal and electronic transport properties of wrinkled SnSe monolayer, but also shed some light on the theoretical design of low dimensional SnSe-layered material in thermoelectric applications. [ABSTRACT FROM AUTHOR]

Magnetic thin-film modeling stands as a dynamic nexus of scientific inquiry and technological advancement, poised at the vanguard of materials science exploration. Leveraging a diverse suite of computational methodologies, including Monte Carlo simulations and molecular dynamics, researchers meticulously dissect the intricate interplay governing magnetism and thin-film growth across heterogeneous substrates. Recent strides, notably in multiscale modeling and machine learning paradigms, have engendered a paradigm shift in predictive capabilities, facilitating a nuanced understanding of thin-film dynamics spanning disparate spatiotemporal regimes. This interdisciplinary synergy, complemented by avantgarde experimental modalities such as in situ microscopy, promises a tapestry of transformative advancements in magnetic materials with far-reaching implications across multifaceted domains including magnetic data storage, spintronics, and magnetic sensing technologies. The confluence of computational modeling and experimental validation heralds a new era of scientific rigor, affording unparalleled insights into the real-time dynamics of magnetic films and bolstering the fidelity of predictive models. As researchers chart an ambitiously uncharted trajectory, the burgeoning realm of magnetic thin-film modeling burgeons with promise, poised to unlock novel paradigms in materials science and engineering. Through this intricate nexus of theoretical elucidation and empirical validation, magnetic thin-film modeling heralds a future replete with innovation, catalyzing a renaissance in technological possibilities across diverse industrial landscapes. [ABSTRACT FROM AUTHOR]

Since the prediction of multi‐hydrogen high‐temperature superconductor by Ashcroft in 2004, many possible candidates have been proposed, e.g., LaH10 showing the highest superconducting transition temperature (Tc) around 250–260 K at 170‐200 GPa hitherto. However, this pressure is too large to be taken into practical use. To address this challenge, it proposes a few‐hydrogen metal‐bonded perovskite superconductor, MgHCu3, by combining a novel design idea with first‐principles calculations. Different from multi‐hydrogen hydrides, whose high Tc relies on extreme pressure, the metallic bond in few‐hydrogen superconductor MgHCu3 improves the structural stability and ductility at atmospheric pressure. Here, the small amount of hydrogen is found to be vital for Tc. After the incorporation of hydrogen, the electron–phonon coupling constant of MgHCu3 is increased to 0.83, which is larger than that of the well‐known MgB2. Moreover, the anisotropy of MgHCu3 also plays an important role in enhancing Tc. Based on the Migdal‐Eliashberg theory, it predicts that the phonon‐mediated metal‐bonded perovskite MgHCu3 is a superconductor with Tc of 42 K. The first predicted ternary metal‐bonded perovskite, MgHCu3, enriches the family of perovskite and will promote further investigation on few‐hydrogen superconductors under atmospheric pressure. [ABSTRACT FROM AUTHOR]

The Dzyaloshinskii–Moriya interactions (DMIs) of Cr2O2ClI Janus monolayer are investigated using the first‐principles calculations. There are three DMI mechanisms (namely, the Half–Fert–Levy mechanism, the Fert–Levy mechanism, and the Rashba mechanism) in Cr2O2ClI Janus monolayer. The Half–Fert–Levy mechanism, by which the I atoms enhance the spin orbit coupling interaction on the type‐I Cr atoms but have no such effect on the type‐II Cr atoms, contributes to the y‐component of the DMI vector between two nearest‐neighbor Cr atoms. Originating from the strong spin orbit coupling interaction of the I atoms, the Fert–Levy mechanism results in a significant DMI vector via the Cr–I–Cr exchange path between two type‐I next‐nearest‐neighbor Cr atoms. Induced by the intrinsic electric field of the Janus structure, the Rashba mechanism results in nonzero in‐plane components of the DMI vectors. This work provides the first‐principles calculations of the DMIs of Cr2O2ClI Janus monolayer and reveals insight into the physics behind the calculated DMIs, which promote the understanding of the complicated DMIs due to multiple mechanisms in 2D magnetic Janus monolayers. [ABSTRACT FROM AUTHOR]

In this paper, a first-principles study of the stability, electronic structure, and magnetic and optical properties of transition metal (TM)-doped monolayer TiS2 systems has been carried out based on the GGA + U methodology under density functional theory. Formation energies, binding energies, phonon spectra, and molecular dynamics calculations indicate the stability of the systems. The Mn-, Fe-, and Co-doped systems exhibit magnetic narrow-band semiconductor properties, with Mn doping inducing the most sizable net magnetic moments. The V- and Mo-doped systems demonstrate magnetic-metallic properties, and incorporating Nb, Ta, and W gives the monolayer TiS2 system semi-metallic properties. The absorption band edges of the doped systems are all redshifted, in which V and Mo doping produces strong orbital hybridization at the Fermi energy level, generates new dielectric peaks in the low-energy region, and extends the absorption range of infrared light, which significantly enhances the optical response of the system. This study provides a theoretical reference for the application of monolayer TiS2 in nanospin and optoelectronics. [ABSTRACT FROM AUTHOR]

MoCoB‐based cermets have been regarded as the potential substitution of WC cermets with high hardness, high melting point and high oxidation resistance. Ternary borides‐based cermets are widely used in extreme environment, such as high‐pressure environment. Therefore, it is significant to explore the mechanical properties and electronic structures of transition elements X (X = V, Mn, Fe, Ni) atoms doped MoCoB under high pressure, which are performed by first‐principles calculations to provide guidance for industry applications. The analysis of cohesive energy and formation enthalpy indicates high pressure leads to unstable states with lower lattice constants and crystal volumes. The deviation of cohesive energy and formation enthalpy indicate Mo4Co3FeB4 and Mo4Co3NiB4 have similar stability. The shear modulus, Young's modulus and bulk modulus increase under high pressure, which consists with the increasing of covalence. The variation of ductility and anisotropy indicate similar upward trend, which is verified by Poisson's ratio, B/G ratio and anisotropy index AU. The analysis of overlap population indicates high pressure leads to the increasing of covalence of B‐Co covalent bonds and the decreasing of the covalence of B‐Mo covalent bonds. The analysis of electronic structures indicates the high pressure leads to higher hybridization and lower density of states of metallic bonds. The analysis of charge density difference consists with the variation of mechanical properties, implying shorter bond length and higher bonds strength under high pressure. [ABSTRACT FROM AUTHOR]

Based on two-dimensional green phosphorene, we designed two molecular electronic devices with zigzag (Type 1) and whisker-like (Type 2) configurations. By combining density functional theory (DFT) and non-equilibrium Green's function (NEGF), we investigated the electronic properties of Types 1 and 2. Type 1 exhibits an interesting negative differential resistance (NDR), while the current characteristics of Type 2 show linear growth in the current–voltage curve. We studied the electronic transport properties of Type 1 under uniaxial strain modulation and find that strained devices also exhibit a NDR effect, and the peak-to-valley ratio of device could be controlled by varying the strain intensity. These results show that the transport properties of green phosphorene with different edge configuration are different, and the zigzag edge have adjustable negative differential resistance properties. [ABSTRACT FROM AUTHOR]

In order to control the production cost of lacquer products, Cu–ethanolamine nanozymes were synthesized to simulate laccase to catalyze the oxidation and polymerization of urushiol. First-principles calculation results indicate that the D-band center of Cu center in the nanozymes was closer to the Fermi level than that of laccase, so Cu–ethanolamine was more conducive to the adsorption of substrate. The activation energy of Cu-ethanolamine catalyzed the oxidation of urushiol was significantly lower than that of laccase. Therefore, we inferred that the synthesized Cu–ethanolamine had a better catalytic effect on urushiol and was more conducive to paint film drying. By comprehensive comparison, the drying characteristics of the Cu–ethanolamine and raw lacquer with a 1:20 ratio are found to be closest to those of the raw lacquer, and the drying time is significantly shortened. The reaction results of the drying process performance test on the sample indicate that the composite lacquer can achieve the market-desired effect and performance requirements of the paint process. [ABSTRACT FROM AUTHOR]

The dispersion of reinforced particles is crucial in improving the mechanical properties of ceramic particles reinforced Al matrix composites. In this work, a novel interfacial projection strategy was proposed to improve the dispersion of TiB2 particles in Al-Si composites through high-throughput first-principles calculations with the experimental verification. Firstly, the Al(111)/TiB2(0001) interface model was constructed. Then, the pre-substitution of Si at 2 at. % concentration was employed to simulate the solutionized Al matrix. Secondly, alloying behaviors of 55 elements (10 substitution sites per element) in the Si-Al(111)/TiB2(0001) interface were studied by high-throughput first-principles calculations in terms of the relative interface formation energy and the relative work of adhesion. With these values, a theoretical alloying map for evaluating the dispersion ability of these alloying elements was plotted. Accordingly, the copper mold experiments were conducted to validate the theoretical alloying map. Based on the electron analysis, the enhanced interface bonds by alloying primarily attributed to electron accumulations around Si atom, indicating that the pre-substitution Si atom was vital for a reliable simulation result. Generally, this interfacial projection strategy provides a precise and potent approach in designing high-performance Al matrix composites, and should be applicable to other reinforced particles.

Combining first-principles calculations and classical nucleation theory, the results of elemental doping on the structure, electrons and stability of niobium carbides are investigated. Ti, Cr and Mn doping altered the physical characteristics of the carbides, resulting in lower mismatch strains and interfacial energies between the carbide and the substrate. Elemental doping reduced the critical nucleation size of carbides and contributed to the promotion of carbide nucleation. However, excessive doping with Cr and Mn increases the formation energy of carbides and unfavorable to carbide stabilization. Therefore, Cr and Mn are involved in the early elemental aggregation of carbides, while Ti and Nb are the main carbide-forming elements. The nano-precipitated phases of various compositions produced in niobium microalloyed steel were experimentally validated utilizing transmission electron microscopy (TEM) and three-dimensional atom probe tomography (3D-APT). The carbides primarily composed of Nb, Ti and C elements, with the presence of Cr and Mn in the core region leading to the formation of a core-shell structure, which is consistent with theoretical calculations.

A novel Mg-Nd-Sm-Zn-Zr alloy with promising age-strengthening effects has been successfully developed to meet the urgent needs of lightweight in the aerospace industry. The precipitation behavior and elastic properties of the nano-precipitates in the alloy have been revealed using transmission electron microscopy and first-principles calculation. The Guinier-Preston (GP) zones, lamellar γ′ precipitates, and granular β′ precipitates formed in the α-Mg matrix after aging at 190 °C for 3 h (under-aging stage). Notably, the alloy reached the peak-aging stage and achieved an excellent ultimate tensile strength of 266 MPa after aging for 18 h. These precipitates further transformed into the lamellar β′ and β1 precipitates, and the enclosed nano-strengthening structure was constructed by γ′, β′ and β1 precipitates. The precipitation sequence of the aged alloy was determined as the supersaturated solid solution (SSSS) → GP zones → β′/γ′ → β1. First-principles calculations and 3D visualization approach demonstrated that the addition of mixed light RE elements can effectively improve the elastic modulus and reduce the elastic anisotropy of β′ nano-precipitates. The Young's modulus (E), shear modulus (G), and anisotropy index (AU) of β′-Mg7(Nd,Sm) precipitates were 48.38 MPa, 18.79 MPa and 2.29, respectively. This study provides a theoretical and experimental basis for further research and development of novel high-performance Mg-light RE alloys.

The formation and evolution of SmCo5/Sm2Co17 (1:5H/2:17R/H) cellular structures play an essential role in understanding the coercivity of Sm-Co magnets. Herein, the pristine and different elemental-doped 1:5/2:17R and 1:5/2:17H interfaces are investigated to evaluate the elemental site preferences, interface configurations, and magnetic properties in Sm2Co17-type magnets with general alloy elements M (M = Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Al, Si, and Ga). Comparing the calculated results of 1:5/2:17H with those of the 1:5/2:17R interface, we found that Cu and Mn always segregate at the 1:5 phase, and Ga elements first appear at the 1:5 phase in 1:5/2:17H and then change to the 2:17 phase in 1:5/2:17R. While Ti, V, Fe, Zn, Al, and Si elements always tend to segregate at the 2:17 phase, Ni first segregates at the 2:17 phase in 1:5/2:17H and then occupies the 1:5 phase of 1:5/2:17R. The 1:5/2:17H interface along the c-axis expands about 1.98~3.28%, while the 1:5/2:17R interface slightly shrinks about 0.04~0.87% after element doping. This suggests that different interface stress behaviors exist for high-temperature and room-temperature phase Sm2Co17-type magnets. Furthermore, Mn, Fe, and Ga doping improved the saturation magnetization strength. Our results provide new insights into understanding the effect of elemental doping at the interfaces of 1:5H/2:17R cellular structures.

In the present study, the effect of the Nb element on the lattice parameters, phase stability and martensitic transformation behaviors of Ti-Zr-based shape memory alloys was extensively investigated using the first-principles calculation. The lattice parameters of both the β parent phase and α′ martensite phase gradually decreased with Nb content increasing. For the α″ martensite phase, the lattice constant (a) gradually increased with the increase in Nb content, whereas the lattice constants (b and c) continuously decreased due to the addition of Nb. Based on the formation energy and density of state, β→α′ martensitic transformation occurred, as the Nb content was not more than 12.5 at.%. However, the Ti-Zr-Nb shape memory alloys with a Nb content higher than 12.5 at.% possessed the β→α″ martensitic transformation. However, both the largest transformation strain and sensitivity of critical stress to temperature (dσ/dT) can be optimized by controlling 12.5 at.% Nb in the Ti-Zr-Nb shape memory alloy, which was favorable to obtaining the largest elastocaloric effect.

First-principles calculations were used to determine the formation energy, work of adhesion, and electronic structure of the interface of Ag-doped (Cu, Sn, and Ti)/WC, revealing the effect of doping atoms on the interfacial bonding behavior. Additionally, an active filler metal Ag–Cu–Sn–Ti was developed from the calculation results and applied to braze YG18 cemented carbide/40Cr steel joint. The interfacial structure and elemental diffusion behavior at the filler metal/WC interface were characterized. The doping of Cu and Ti at the interface contributes significantly to the stability of the interfacial structure and the improvement of the work of adhesion. The effect of doping of Sn atoms at different positions on interfacial stability and the work of adhesion is not obvious, and it can be doped into Ag alloys as a melting point depressant. The charge accumulation zone and atomic orbital hybridizations at the interface contributes to enhance the interface stability and the work of adhesion. The TEM analysis demonstrates that the diffusion behavior of Ti is particularly noticeable, aggregating at the Ag/WC interface and interacting with C to generate a TiC reaction layer, ultimately producing a WC/TiC/Ag interface structure.

The effect of cobalt on the precipitation hardening behavior of the maraging stainless steels was studied. The hardness test indicated that cobalt addition could advance peak aging time and generate a higher peak hardness. The statistical results of nano-size precipitates distribution demonstrated that cobalt increased the density of precipitates, thus resulting in a stronger precipitation hardening contribution. Based on the first-principles calculations and atom probe tomography (APT) results, a possible mechanism has been proposed to reveal the underlying mechanism: cobalt promotes the nucleation of precipitates by decreasing the diffusion activation energy of Ni and Ti.

The lattice square degree, denoted by the c/a value, is a crucial factor that influences the slip mode of α-Ti alloys and thereby affects their plasticity. However, the relationship between the c/a value and the plasticity of α-Ti alloys has not been fully clarified. In this study, the powder metallurgy method (PM) was used to prepare Ti alloys with different square degrees by introducing interstitial O and substitutional Si solutes into α-Ti crystal. Then the mechanical properties, particularly plasticity, and lattice parameters of the resulted alloys were measured. By combining first-principles calculation with experimental studying, a plastic criterion based on the square degree was established. Subsequently, the mechanism of strength and plasticity was investigated by means of the density of states and charge density difference. Finally, the composition of α-Ti alloys with both O and Si solution atoms was designed, whose c/a values were calculated by the first-principles calculation and accorded with the proposed square degree criterion, and then the reliability of this criterion was verified by the experimental results. As a result, a high strength and plasticity α-Ti alloy with tensile strength 1106 MPa and elongation 23.2 % was successfully prepared. The findings of this research offer new insights into the alloying design of α-Ti alloys with high strength and moderate plasticity.

The introduction of oxide inclusions during the smelting process has a clear promising heterogeneous nucleation potency on Mg-based alloys, but the mechanism has not been explored clearly yet. In the present work, the grain refinement mechanism of MgO in pure Mg, Mg-3Al and AZ31 (Mg-2.9Al-0.9Zn-0.3Mn) alloys is investigated by combing first-principles calculations and experiments. The theoretical results show that solute atoms adsorption will affect the nucleation and the subsequent growth process, which is an important factor affecting the refinement efficiency. A contradiction between the experimental results and the grain growth restriction factor (GRF) theory is observed, that is the refinement ratio of AZ31 is worse than Mg-3Al alloy. This is explained by an adsorption model which reveals that Al promotes the adsorption of Mg on MgO surface so as to stimulate more particles available as nucleating sites. Meanwhile, Fe and Mn also have favorable effects on the adsorption of Mg, Zn may play the opposite role compared to Al. The theoretical analyzes provide a strong support to the experiments that Al benefits the initial nucleation of α-Mg on MgO to promote the grain refining effect of Mg-3Al prior to AZ31 alloy.

The electrochemical reduction of CO2 is an extremely potential technique to achieve the goal of carbon neutrality, but the development of electrocatalysts with high activity, excellent product selectivity, and long-term durability remains a great challenge. Herein, the role of metal-supports interaction (MSI) between different active sites (including single and bimetallic atom sites consisting of Cu and Ni atoms) and carbon-based supports (including C2N, C3N4, N-coordination graphene, and graphdiyne) on catalytic activity, product selectivity, and thermodynamic stability towards CO2 reduction reaction (CRR) is systematically investigated by first principles calculations. Our results show that MSI is mainly related to the charge transfer behavior from metal sites to supports, and different MSI leads to diverse magnetic moments and d-band centers. Subsequently, the adsorption and catalytic performance can be efficiently improved by tuning MSI. Notably, the bimetallic atom supported graphdiyne not only exhibits a better catalytic activity, higher product selectivity, and higher thermodynamic stability, but also effectively inhibits the hydrogen evolution reaction. This finding provides a new research idea and optimization strategy for the rational design of high-efficiency CRR catalysts.