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This article utilizes first‐principles calculations within the density functional theory framework, employing spin generalized gradient approximation, to investigate the spin polarization of arsenic nitride nanotubes (AsNNTs). It is found that AsNNT does not exhibit spin polarization and has a bandgap of 1.05 eV, indicating that it is a semiconductor. Decoration with C, O, Ge, and Se on AsNNT induces spin polarization, resulting in magnetic moments of 1.001, 0.916, 0.770, and 0.967 μB, respectively. Meanwhile, all decorated configurations exhibit narrow bandgap semiconductor properties. Furthermore, the nonequilibrium Green's function method is used to study the spin‐polarized current of AsNNT decorated with C, O, Ge, and Se. It is found that AsNNTs decorated with C, Ge, and Se have relatively small spin current values. Notably, the Se‐decorated AsNNT exhibits the highest degree of spin polarization, with the spin current being nearly fully polarized. [ABSTRACT FROM AUTHOR]

With the rapid growth of the world population and economy, the greenhouse effect caused by CO2 emissions is becoming more and more serious. To achieve the "two-carbon" goal as soon as possible, the carbon dioxide reduction reaction is one of the most promising strategies due to its economic and environmental friendliness. As an analog of graphene, monolayer h-BN is considered to be a potential catalyst. To systematically and theoretically study the effect of O doping on the CO2 reduction catalytic properties of monolayer h-BN, we have perform a series of first-principle calculations in this paper. The structural analysis demonstrates that O preferentially replaces N, leading to decreasing VBM of monolayer h-BN, which is conducive to improving its capability for CO2 reduction. The preferential CO2 adsorption sites on monolayer h-BN before and after O doping are the N-t site and B-t site, respectively. O doping increases the adsorption strength of CO2, which is favorable in the further hydrogenation of CO2. During the conversion of CO2 into CO and HCOOH via a two-electron pathway and CH3OH and CH4 via a six-electron pathway, O doping can reduce the energy barrier of the rate determining step (RDS) and change the key steps from uphill reactions to downhill reactions, thus increasing the probability of CO2 reduction. In conclusion, O(N)-doped h-BN exhibits the excellent CO2 reduction performance and has the potential to be a promising catalyst. [ABSTRACT FROM AUTHOR]

In this paper the piezoelectric effects in infinite free-standing HfO2 film and HfO2 cluster under mechanical action are studied by methods of the density functional theory and first-principles pseudopotential based on own program code. The spatial distribution of valence electron density, the forces that act on an individual atom from the electronic and ionic subsystems, and Coulomb potential along transverse direction are calculated. It was found that a polarization charge distribution of valence electrons, which leads to piezoelectric effects, was observed in HfO2 nanofilms, while in HfO2 nanoclusters the charge distribution remained uniform both in the uncompressed and in the compressed state. [ABSTRACT FROM AUTHOR]

The effect of the Mn3+ ion on the local distortions of FeO6 octahedra in orthoferrite samples was investigated. Mössbauer spectroscopy measurements for a series of HoFe 1 − x Mn x O 3 (x = 0–0.7) orthoferrite samples with the space group Pnma were carried out at temperatures above the Néel point (700 K). The electric field gradient (EFG) tensor on Fe ions for these compounds was found using first-principle calculations. The concentration dependence of quadrupole splitting was obtained using experimental and theoretical data. Mn3+ cations were found to affect the Mössbauer spectra mainly due to distortions of the crystal lattice. Theoretical calculations show that the values of all electric field gradient components increase significantly with the manganese concentration in the system, and the eigenvectors e xx and e yy of the electric field gradient tensor sharply change their direction at concentrations of x > 0.1. [ABSTRACT FROM AUTHOR]

Abstract First-principle calculations based on density functional theory are employed to investigate the impact of graphene insertion on the electronic properties and Schottky barrier of MoS2/metals (Mg, Al, In, Cu, Ag, Au, Pd, Ti, and Sc) without deteriorating the intrinsic properties of the MoS2 layer. The results reveal that the charge transfer mainly occurs at the interface between the graphene and metal layers, with smaller transfer at the interface between bi-layer garphene or between graphene and MoS2. And the tunneling barrier exists at the interface between graphene and MoS2, which hinders electron injection from graphene to MoS2. Importantly, the Schottky barrier height ( $$\Phi_{{\text{SB,N}}}$$ Φ SB,N ) decreases upon graphene insertion into MoS2/metal contacts. Specifically, for single-layer graphene, the $$\Phi_{{\text{SB,N}}}$$ Φ SB,N of MoS2 contacted with Mg, In, Sc, and Ti are − 0.116 eV, − 0.116 eV, − 0.014 eV, and − 0.116 eV, respectively. Furthermore, with bilayer graphene, when by inserting bi-layer graphene, the negative n-type Schottky barrier of − 0.086 eV, − 0.114 eV, − 0.059 eV, − 0.008 eV, and − 0.0636 eV are observed for MoS2 contacted with the respective metals, respectively. These findings provide a practical guidance for developing and designing high-performance transition metal dichalcogenide nanoelectronic devices.

First-principles density functional formulation was used to explore the electronic and optical properties of magnesium chalcogenides sulfides, MgXS3 (X = Ti and Zr), which compose of magnesium titanium sulfide, MgTiS3, and magnesium zirconium sulfide, MgZrS3. The lattice parameter calculations for MgZrS3 yielded 9.19 Å, a bulk modulus of 170.6 GPa, and an equilibrium volume of 423.03 Å3. In contrast, MgTiS3 yielded 9.27 Å, a bulk modulus of 251.3 GPa, and an equilibrium volume of 117.06 3 Å3. The computation gave a direct bandgap value for MgTiS3 and MgZrS3 of 1.1 eV and 1.3 eV, respectively. The dielectric constants of 38 and 32 were observed for the imaginary and real values for energy equivalents of 0.7 eV and 1.35 eV. The determined dielectric constants and energy values of the perovskite compounds were 70 and 1.35 eV respectively with their point of intersection also at this bandgap value. The efficiency of the compounds was calculated using the spectroscopic limited maximum efficiency (SLME) in order to ascertain their output as absorber materials. The findings show that MgZrS3 had a higher efficiency value of 32.54% and MgTiS3 with 29.45%. These compounds’ computed properties point to the possibility of creating inexpensive, non-toxic absorber layer materials for use in solar cell development and other electronic applications.

Ti doping can improve the interfacial wettability and bonding condition between ZTA ceramic and high chromium cast iron (HCCI), but the underlying mechanism is still unclear. Therefore, the effects of Ti doping on the interfacial characters between ZTA and HCCI were investigated by experiment and first-principles calculations. Results of XRD, SEM, and high-temperature drop test indicate the presence of Ti at the interface and its effect on the formation of interfacial diffusion layer to improve the interface wettability and bonding obviously. The heat of segregation and work of adhesion obtained by first-principle calculations shows that the improvement in interface wettability and bonding is due to the promotion of dopped Ti atoms on the diffusion of Fe, Al, and Zr elements, but not the diffusion of Ti itself. Further investigation from the electronic level reveals that the doped Ti changes the charge distribution and orbital hybridization, and thus makes the formation or enhancement of strong ionic bonds and covalent bonds at the interface, improving the bonding strength and wettability of interfaces in ZTA/HCCI. The findings of this research can offer new insights into the modification of ceramics and enlarge the application of advanced ceramic materials. [ABSTRACT FROM AUTHOR]

We conducted first-principles calculations to investigate the behavior of hydrogen (H) in dilute copper-nickel-aluminum (Cu–Ni–Al) alloys. Single H favors the octahedral interstitial site (OIS) in the presence of Ni/Al/iron (Fe) atom. Ni and Fe reduce the solution energy of H while Al increases it. The interactions between H and Ni/Al/Fe are short-range effect within the 1nn shell, Ni/Fe can attract H with binding energy of 0.22/0.30 eV while Al repels H. We determined the aggregation behavior of H in Ni/Fe/Al region, single Ni/Fe can stably trap up to 6 H atoms, and the Fe-H n complex is more stable than Ni-H n one. Furthermore, we predicted the effect of Ni/Al/Fe on the solubility, diffusivity and permeability of H by empirical formulas. H prefers to dissolve in the 1nn shell of Ni and Fe, reducing the effective diffusion rate of H. Ni and Fe increase the permeability of H while Al decreases it in Cu alloys. Kinetically, H tends to migrate via octahedral-tetrahedral-octahedral path with the barrier of 0.34 eV in pure Cu, and Ni/Fe reduces the H migration barrier by 0.07 eV while Al increases it by 0.11 eV. These results deepen the understanding of the solute-H interaction in Cu alloys. [Display omitted] • Ni/Fe enhances H solubility in Cu alloys. • The repulsive effect of Al on H promotes its dissolution near Ni/Fe. • Al's repulsive effect promotes H dissolution near Ni/Fe. • Ni/Fe increases H permeability in Cu alloys, while Al decreases it. [ABSTRACT FROM AUTHOR]

In this paper, we designed g-ZnO/HfZrCO2 van der Waals heterostructures (HS) by stacking g-ZnO and HfZrCO2 monolayers together to search sunlight-driven water-splitting photocatalyst. Then we selected the two most stable structures between them, AA-HS and AK-HS, for further study. The AK-HS shows a type-I band arrangement, which is not suitable as a photocatalyst for water splitting; while the AA-HS belongs to a type-II band alignment semiconductor. To regulate its band structure, different biaxial strains parallel to the stacking layers from −2% to 2% are applied on AA-HS. The results show AA-stacking HS under compressive strains exhibit typical type-II band arrangement with a staggered gap. Further investigations show that the band edges of AA-HS under a compressive strain of 0.5% meet the requirement of water redox potentials at PH 0. In addition, the absorption coefficients of AA-HS under the compressive strain of 0.5% were calculated, and the results it has good optical absorption of sunlight. The excellent photoelectric and catalytic properties make the AA-HS under compressive strain of 0.5% as a potential sunlight-driven catalyst for water splitting in a strong acid environment. [ABSTRACT FROM AUTHOR]

Electrochemical nitrogen reduction reaction (NRR) is a promising route for realizing green and sustainable ammonia synthesis under ambient conditions. However, one of the major challenges of currently available Single-atom catalysts (SACs) is poor catalytic activity and low catalytic selectivity, which is far away from the requirements of industrial applications. Herein, first-principle calculations within the density functional theory were performed to evaluate the feasibility of a single Mo atom anchored on a g-C9N10 monolayer (Mo@g-C9N10) as NRR electrocatalysts. The results demonstrated that the gas phase N2 molecule can be sufficiently activated on Mo@g-C9N10, and N2 reduction dominantly occurs on the active Mo atom via the preferred enzymatic mechanism, with a low limiting potential of −0.48 V. In addition, Mo@g-C9N10 possesses a good prohibition ability for the competitive hydrogen evolution reaction. More impressively, good electronic conductivity and high electron transport efficiency endow Mo SACs with excellent activity for electrocatalytic N2 reduction. This theoretical research not only accelerates the development of NRR electrocatalysts but also increases our insights into optimizing the catalytic performance of SACs. [ABSTRACT FROM AUTHOR]

Lead-free double perovskites with tunable bandgap are emerging as a potential candidate for solar cell applications due to their high absorption coefficient, large structural stability, and environmentally friendly nature. In this work, Li2CuSbZ6 (Z = Cl, Br, I) double perovskites have been examined utilizing the FP-LAPW approach in WIEN2k software. Modified Becke-Johnson exchange-correlation potential and BoltzTrap code are adopted to calculate the optoelectronic and thermoelectric characteristics. The results showed that the DPs had negative formation energies and stable structures. Born stability criteria exhibited their mechanical stability. All compounds are semiconductors having direct band-gaps of 1.7, 1.3, and 0.9 eV for Li2CuSbCl6, Li2CuSbBr6, and Li2CuSbI6, respectively. Orbital contributions are later investigated through partial (PDOS) and total (TDOS) density of states calculations. Optical response analysis revealed that these perovskites are characterized by low energy loss and higher absorption in the visible region making them good candidates for solar cell devices. Additionally, their thermoelectric response such as the high figure of merit, Seebeck coefficients, and low thermal conductivity exposed their potential for conversion devices. [ABSTRACT FROM AUTHOR]

Fe-containing intermetallic compounds (IMCs) are among the most detrimental second phases in aluminum alloys. One particularly harmful type is θ-Al13Fe4, which exhibits a needle- or plate-like morphology, leading to greater degradation of mechanical properties compared to other Fe-IMCs with more compact structures, such as α-Al15(Fe,Mn)3Si2. The addition of alloying elements is a crucial strategy for modifying the microstructure during the solidification process of aluminum alloys. This study investigates the effects of adding vanadium (V) and zirconium (Zr) on the morphology and crystal chemistry of θ-Al13Fe4 in an Al-4Fe alloy, employing a combination of experimental observations, first-principle calculations, and thermodynamic analysis. Our findings indicate that zirconium significantly refines both the primary θ-Al13Fe4 particles and the α-Al grains. Additionally, a small amount of vanadium can be incorporated into one of the Wyckoff 4i Al sites in θ-Al13Fe4, rather than occupying any Fe sites, under casting conditions, in addition to the formation of binary Al-V phases. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) polarized heterostructures with internal electric fields are potential photocatalysts for high catalytic performance. The Blue P/SiS van der Waals heterostructures were formed from monolayer Blue P and polar monolayer SiS with different stacking interfaces, including Si-P and P-S interfaces. The structural, electronic, optical and photocatalytic properties of the Blue P/SiS heterostructures were studied via first-principle calculations. The results showed that the Si-P-2 or P-S-4 stacking order contributes to the most stable heterostructure with the Si-P or P-S interface. The direction of the internal electric field is from the 001 surface toward the 00 1 ¯ surface, which is helpful for separating photo-generated electron–hole pairs. The bandgap and electrostatic potential differences in the Si-P-2(P-S-4) heterostructures are 1.74 eV (2.30 eV) and 0.287 eV (0.181 eV), respectively. Moreover, the Si-P-2(P-S-4) heterostructures possess suitable band alignment and wide ultraviolet and visible light spectrum regions. All results suggest that 2D polarized Blue P/SiS heterostructures are potential novel photocatalysts for water splitting under a wide ultraviolet and visible light spectrum region. [ABSTRACT FROM AUTHOR]

Transition metal nitrides, especially tantalum nitrides, are pivotal for applications in extreme environments demanding excellent mechanical properties and thermodynamic stability. Among them, θ$\utheta$‐TaN, a high‐pressure polymorph of tantalum nitride with its exceptional bulk modulus (362 GPa) and hardness (31.7 GPa) promises to have many technological uses. Another nitride, Ta3N5${\rm {Ta}}_3{\rm {N}}_5$, has gained importance as a photocatalyst for water splitting using visible light. The Ta–N phase diagram indicates that the thermal decomposition of pure Ta3N5${\rm {Ta}}_3{\rm {N}}_5$ leads to the formation of ε$\uepsilon$‐TaN. However, Ta3N5${\rm {Ta}}_3{\rm {N}}_5$ usually has some amount of oxygen as an impurity mainly due to its synthesis route. We found that the θ$\utheta$‐TaN phase, which is usually observed at high pressures, is formed during the thermal decomposition of oxygen containing Ta3N5${\rm {Ta}}_3{\rm {N}}_5$. The presence of θ$\utheta$‐TaN is verified using several experimental techniques such as X‐ray diffraction, Raman spectra, high‐angle annular dark field scanning transmission electron microscopy (STEM‐HAADF), and electron energy loss spectroscopy (EELS). Elemental distribution analyzed through energy dispersion X‐ray spectroscopy (XEDS) in STEM reveals about 7 at.% of oxygen in θ$\utheta$‐TaN. First‐principle calculations are performed to examine the thermodynamic stability of oxygen substituted θ$\utheta$‐TaN and pure θ$\utheta$‐TaN via formation enthalpies, elastic constants, and phonon dispersion calculations. The computational studies confirm that oxygen in θ$\utheta$‐TaN enhances its thermodynamic stability. The calculated electron localization functions establish the bonding characteristics between Ta, N, and O, confirming the same. [ABSTRACT FROM AUTHOR]

We employ the full-potential linear augmented plane wave method, utilizing the density functional theory in the generalized gradient approximation with the modified Becke-Johnson potential (GGA + mBJ) to investigate the properties of Heusler quaternary CoZrFeZ compounds (Z = As, Sb). The study includes an analysis of the structural, elastic, electronic, and magnetic characteristics of these compounds. The results indicate that both compounds exhibit a half-metallic behavior for the minority spin, with a total magnetic moment of 2 µB, following the Slater–Pauling rule. Furthermore, the calculated data reveal that the elastic constants and phononic dispersions of the CoZrFeAs and CoZrFeSb compounds suggest mechanical and dynamical stability in phase Y(I), accompanied by negative formation energies. This implies that these systems are stable and can be synthesized. In light of these encouraging results, Heusler quaternary CoZrFeZ compounds (Z = As, Sb) appear as promising candidates for applications in spintronics and magnetoelectronics. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials present novel electronic and catalytic performances, showing a promising application as nano-device. In this investigation, a family of 2D material, X2B6 (X = K, Na and Rb), is predicted with puckered crystal structure by elemental mutation method. The dynamic and thermal stability of the X2B6 monolayer is addressed. The anisotropic mechanical properties of the X2B6 monolayer is obtained by the Young’s modulus (296–406 N/m) and the Poisson’s ratio (0.36–0.35). Interestingly, the K2B6 and Rb2B6 monolayers demonstrate a metallic band structure, while the Na2B6 monolayer is a semiconductor with an ultra-narrow bandgap only about 0.42 eV. Then, the ultra-high electron mobility in the Na2B6 monolayer is calculated as about 9942 cm2.V−1.s−1, and the excellent optical performance of the Na2B6 monolayer is also addressed. More importantly, the advantageous catalytic activity in hydrogen evolution reduction (HER) and oxygen evolution reactions (OER) is explored in these X2B6 monolayers. Our work suggests a theoretical guidance to use the X2B6 monolayer as a high-speed electronic devices and highly efficient catalyst.

Defect single-photon emitters (SPE) in gallium nitride (GaN) have garnered great attentions in recent years due to the advantages they offer, including the ability to operate at room temperature, narrow emission linewidths, and high brightness. Nevertheless, the precise nature of the single-photon emission mechanism remains uncertain due to the multitude of potential defects that can form in GaN. In this work, our systematical investigation with the ab initio calculation indicates that carbon and silicon, as common dopants in gallium nitride, can interact with intrinsic defects in GaN and form new high-speed defect single-photon sources. Our findings identify a ternary defect NGaVNCN that possesses a short lifetime of less than 1 ns and a small zero-photon line (ZPL) of 864 nm. In other words, this defect can serve as a high-speed single photon source in the short wavelength window for fiber communication. In sharp contrast, the Si-supported defect NGaVNSiN has a higher unoccupied defect energy level which enters the conduction band and is therefore unsuitable for single photon emission. A systematic investigation has been conducted into the potential defects, thermal stability, and single-photon emission properties. The relaxation calculation and self-consistent calculations employed the Perdew–Burke–Ernzerhof exchange-correlation functional and Heyd–Scuseria–Ernzerhof exchange-correlation functional, respectively. These findings indicate the potential for high-performance single-photon sources through carbon or silicon doping of GaN. [ABSTRACT FROM AUTHOR]

Stacking engineering is a popular method to tune the performance of two dimensional materials for advanced applications. In this work, Jansu MoSSe and WSSe monolayers are constructed as a van der Waals (vdWs) heterostructure by different stacking configurations. Using first-principle calculations, all the relaxed stacking configurations of the MoSSe/WSSe heterostructure present semiconductor properties while the direct type-II band structure can be obtained. Importantly, the Z-scheme charge transfer mode also can be addressed by band alignment, which shows the MoSSe/WSSe heterostructure is an efficient potential photocatalyst for water splitting. In addition, the built-in electric field of the MoSSe/WSSe vdWs heterostructure can be enhanced by the S-Se interface due to further asymmetric structures, which also results in considerable charge transfer comparing with the MoSSe/WSSe vdWs heterostructure built by the S-S interface. Furthermore, the excellent optical performances of the MoSSe/WSSe heterostructure with different stacking configurations are obtained. Our results provide a theoretical guidance for the design and control of the two-dimensional heterostructure as photocatalysts through structural stacking. [ABSTRACT FROM AUTHOR]

Currently, lithium-ion batteries have an increasingly urgent need for high-performance electrolytes, and additives are highly valued for their convenience and cost-effectiveness features. In this work, the feasibilities of fullerenes and fluorinated fullerenes as typical bis(fluorosulfonyl)imide/1,2-dimethoxymethane (LiFSI/DME) electrolyte additives are rationally evaluated based on density functional theory calculations and molecular dynamic simulations. Interestingly, electronic structures of C60, C60F2, C60F4, C60F6, 1-C60F8, and 2-C60F8 are found to be compatible with the properties required as additives. It is noted that that different numbers and positions of F atoms lead to changes in the deformation and electronic properties of fullerenes. The F atoms not only show strong covalent interactions with C cages, but also affect the C-C covalent interaction in C cages. In addition, molecular dynamic simulations unravel that the addition of trace amounts of C60F4, C60F6, and 2-C60F8 can effectively enhance the Li+ mobility in LiFSI/DME electrolytes. The results expand the range of applications for fullerenes and their derivatives and shed light on the research into novel additives for high-performance electrolytes. [ABSTRACT FROM AUTHOR]

Both the intrinsic and extrinsic contributions to the high energy storage properties of (K0.5Na0.5)NbO3 were investigated herein by employing Bi(Mg2/3Ta1/3)O3 as a second component to synthesize novel environment‐friendly energy storage ceramics. The role of the second component was confirmed to reduce the intrinsic activation of electrons, which effectively improves the band gap values and reduces the probability of intrinsic breakdown. Phase field simulation was employed to confirm that the smaller grain size of the modified ceramic microstructure enhances the extrinsic breakdown and dielectric breakdown strength. Moreover, ab initio molecular dynamics were used to investigate the critical role of the Mg ions in lowering the initial polarization and forming nanodomains, representing the intrinsic contribution to decreasing the initial polarization. An intrinsic structure with moderate polarization rapidly increases the polarization of ceramics under external electric fields, facilitating high energy storage density. The prepared ceramics achieve a recoverable energy density (Wrec) of 3.86 J/cm3 and energy efficiency (η) of 81.2% at 385 kV/cm. [ABSTRACT FROM AUTHOR]

The emergence of various topological semimetal states presents a novel opportunity for enhancing the efficiency of thermoelectric transport. This study introduces a recipe to improve the thermoelectric (TE) performance in topological materials containing single‐pair Weyl points (SP WPs) fermions and phonons. The recipe focuses on two key factors contributing to the enhancement of TE performance: the increase in the density of states to achieve a high power factor, and the introduction of additional phonon scattering to reduce the lattice thermal conductivity. The proposed recipe is confirmed in a half‐metallic SP WPs material BaNiIO6 through first‐principles methods. An enhanced density of states arises near the energy of the SP WPs in BaNiIO6, leading to a peak power factor connected to the complex Fermi surface due to the degeneracy of Weyl pockets in energy. Furthermore, it is shown that the SP WPs phonons in BaNiIO6 possess a high scattering rate and can likely contribute to the low lattice thermal conductivity, especially when two crossing points in SP WPs do not degenerate in frequency. The new recipe can be used for discovering high‐performance thermoelectric materials in the future by utilizing the transport advantages of degenerate‐in‐energy SP WPs fermions and non‐degenerate‐in‐frequency SP WPs phonons. [ABSTRACT FROM AUTHOR]

First-principles density functional formulation was used to explore the electronic and optical properties of magnesium chalcogenides sulfides, MgXS3 (X = Ti and Zr), which compose of magnesium titanium sulfide, MgTiS3, and magnesium zirconium sulfide, MgZrS3. The lattice parameter calculations for MgZrS3 yielded 9.19 Å, a bulk modulus of 170.6 GPa, and an equilibrium volume of 423.03 ų. In contrast, MgTiS3 yielded 9.27 Å, a bulk modulus of 251.3 GPa, and an equilibrium volume of 117.06 3 ų. The computation gave a direct bandgap value for MgTiS3 and MgZrS3 of 1.1 eV and 1.3 eV, respectively. The dielectric constants of 38 and 32 were observed for the imaginary and real values for energy equivalents of 0.7 eV and 1.35 eV. The determined dielectric constants and energy values of the perovskite compounds were 70 and 1.35 eV respectively with their point of intersection also at this bandgap value. The efficiency of the compounds was calculated using the spectroscopic limited maximum efficiency (SLME) in order to ascertain their output as absorber materials. The findings show that MgZrS3 had a higher efficiency value of 32.54% and MgTiS3 with 29.45%. These compounds' computed properties point to the possibility of creating inexpensive, non-toxic absorber layer materials for use in solar cell development and other electronic applications. [ABSTRACT FROM AUTHOR]

The conversion of methane in catalysis fields has aroused much attention for its abundant distribution in nature and it is environment-friendly. However, the C–H chemical breaking is a major challenge and requires proper catalysts for methane activation. Using first-principle calculations, we systematically explore the atomic configuration, interaction strength, dehydrogenation process and electronic properties of methane on noble metal Pt(111) and isoelectronic transition metal carbide WC(001) surface. The adsorption strength of methane activation on the WC(001) surface is stronger and the barrier of C–H bond breaking is smaller than that of the Pt(111) surface. Moreover, the oxygen concentration ranging from 40% to 60% coverage on the WC(001) surface benefits the methane activation and the energy barrier decreased to 0.26 ∼ 0.57 eV. The larger charge transfer emerges at the interface between methane and the WC(001) surface with or without oxygen coverage comparable to the Pt(111) surface. Our theoretical results can provide vital guidance for experimental synthesis conditions of methane activation and the transition metal carbide application in catalysts. [ABSTRACT FROM AUTHOR]

Cu6Sn5-xAg alloys (x = 0, 3, 6; %, mass fraction) were synthesized using Ag as a dopant through a high-temperature melting technique. The microstructure of the alloy was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and other equipment, while the hardness of the alloy was measured to investigate the impact of Ag addition on the structure and microstructure of the Cu6Sn5 intermetallic compound. This study explored the influence of varying Ag contents on the properties of Cu6Sn5 intermetallic compounds, with calculations based on first principles revealing the mechanical properties and density of states of η′-Cu6Sn5 and its Ag-doped systems. The results indicated that Cu6Sn5-xAg alloys predominantly existed in three distinct forms, all exhibiting large masses without any impurities or precipitates. First-principle calculations demonstrated that Ag substitution in certain sites suppressed the anisotropy of the Young's modulus of Cu6Sn5, particularly in the Cu1, Cu3, Sn1, and Sn3 positions, while the effect was less significant at the Cu2, Cu4, and Sn2 sites. The introduction of Ag through doping enhanced the covalent bonding within the η′-Cu6Sn5 structure, promoting the formation of a stable (Cu, Ag)6Sn5 structure. [ABSTRACT FROM AUTHOR]

The structure–performance mechanism is essential to achieve comprehensive characteristics for advanced communication system. In the present work, F− ions were adopted to fabricated Li 3 Mg 2 NbO 6- x /2 F x ceramics at a nitrogen atmosphere to modify dielectric characteristics. Correlation between bond characteristics, crystal structure and enhanced microwave dielectric characteristics was investigated through vibration analysis, P–V-L theory, Rietveld refinement, and First-principle calculations. Raman analysis and Rietveld refinement show that F− substitution led to a single phase. First-principle calculations indicates a high energy gap of 3.676 eV and p orbit contributed to Fermi energy. F− substitution led to the increase of Nb O bond ionicity and lattice energy, accounting for the variation in Q×f value and dielectric constant. The τ f value was related to the expansion coefficient of the Li–O bond. Remarkably, the samples (x = 0.08) exhibited comprehensive dielectric characteristics with ε r = 15.9, Q×f = 143,000 GHz and near-zero τ f = −2.1 ppm/°C, proving an effective strategy for collaborative regulation. Based on structure simulation, 5G filter with ultra-low loss and high-suppression was designed through introducing transmission zeros from cross coupling. More specifically, a dielectric filter exhibited an interpolation loss of 0.2 dB at 3.3–3.6 GHz and high attenuations of 15 dB for 20 MHz outside the passband, verifying the feasibility for 5G applications. [ABSTRACT FROM AUTHOR]

This study employs first-principles calculation to investigate the MoSi 2 N 4 /SiC heterojunction. It aims to determine the structure, electronic, and optical properties of the heterojunction and assess the impact of varying vertical electric fields and biaxial strains on these properties. The results show that the MoSi 2 N 4 /SiC heterojunction is a direct bandgap semiconductor, exhibiting a band gap of 0.31 eV. This heterojunction benefits from a built-in electric field originating from the SiC layer and extending to the MoSi 2 N 4 layer. The optical absorption peaks in the ultraviolet region are significantly more intense than those in MoSi 2 N 4 and SiC monolayers, particularly at a wavelength of 172 nm, where the intensity reaches 1.99 × 106 cm−1. The study also shows that an increasing positive vertical electric field leads to a rising band gap. On the other hand, increasing tensile or compressive strain causes a gradual decline in the band gap. Specifically, at a strain of −8 %, the absorption peak intensity reaches 3.4 × 106 cm−1 at 172 nm, and the absorption spectrum broadens to 722 nm at an 8 % strain. In conclusion, the MoSi 2 N 4 /SiC heterojunction shows promise for enhancing the optical properties of two-dimensional materials and offers valuable insights for the development of efficient new ultraviolet devices. [ABSTRACT FROM AUTHOR]

To comprehend the mechanical, electronic, and magnetic properties of chalcogenides HgSm2S/Se4, a DFT-oriented thorough investigation is carried out. The elastic constants and spin-dependent electrical characteristics are determined by using the PBEsol-GGA functional and (mBJ) potential correspondingly. Through optimization, a sufficient amount of energy is discharged by the FM state as compared to nonmagnetic states. By investigating Born stability criteria and formation energy, the structural stabilities of both spinels are verified. The calculated Poisson's and Pugh's ratios showed that both spinels are ductile. The estimation of Curie temperature has supported the existence of a ferromagnetic nature at room temperature. Moreover, the presence of ferromagnetism in both spinels is confirmed by spin-oriented electrical characteristics, owing to the coupling between component states associated with Sm and S/Se. [ABSTRACT FROM AUTHOR]

Bulk phosphorus oxynitride (PON), isoelectronic with SiO2, is confirmed to have many polymorphs as the latter. However, its 2D counterparts have not been studied. In this work, crystal structure exploration and property study are performed on 2D PON with the help of first‐principle calculation. Three 2D PON sheets are found with thermal, dynamical, and mechanical stability and all of them can be viewed as oxygen‐doped known 2D γ phosphorus nitride (γ‐PN). In the studies, it is indicated that they are indirect bandgap materials with gap values larger than 3 eV. The situations of orbital hybridization are discussed and their bonding properties are analyzed. Infrared vibrational spectra of these 2D materials are simulated and the vibrational modes at the Brillouin center are assigned by the factor group analysis. The reasons for the disappearance of some infrared peaks in the simulated spectra are revealed based on the calculated Born effective charges and vibrational eigenvectors. Their piezoelectric stress tensors are computed via density‐functional perturbation method and the piezoelectric strain tensors are also deduced via the calculated elastic constants. In the results, it is uncovered that these 2D PON sheets have considerably greater piezoelectric coefficients than the primitive 2D γ‐PN, which make them promising for nanopiezoelectric use. [ABSTRACT FROM AUTHOR]

Single-phase concentrated solid-solution alloys (CSAs) have exhibited excellent mechanical and radiation tolerance properties, making them potential candidate materials for nuclear applications. These excellent properties are closely related to dislocation movements, which depend on the stacking fault energies (SFEs). In CSAs, SFEs show large fluctuations due to variations in the local atomic environments in the vicinity of the stacking faults. In this work, first-principle calculations were performed to investigate the origin of the fluctuations in the SFEs of the widely studied CSA, NiCoCr, which show a very wide distribution from about −200 mJ/m2 to 60 mJ/m2. Compared to the common understanding that only atoms in close proximity to the stacking fault influence the SFEs in pure metals and dilute alloys, charge redistribution can be observed in several nearby planes of the stacking fault in NiCoCr, indicating that atoms several atomic layers away from stacking fault also contribute to the SFEs. Our analysis shows that Cr plays a major role in the large fluctuation in the SFEs of NiCoCr based on both electronic and magnetic responses. The flexible electronic structure of Cr facilitates easier charge transfer with Cr in several nearby atomic planes near the stacking fault, leading to significant changes in the d-electron number, orbital occupation number, and magnetic moments of Cr. [ABSTRACT FROM AUTHOR]

The fascinating realm of silicon quantum dots (Si QDs) has attracted considerable attention for their exceptional optical characteristics and potential applications in the optoelectronic industry. However, there remains a scarcity of research that directly compares the impacts of diverse surface modification methods on the electronic structure and charge transfer properties of Si QD nanomaterials. Considering this scientific challenge, we employ the first-principle calculations to conduct the following investigations. To begin, we have innovatively introduced the concept of the adjacent coordination number (ACN) to establish a quantitative correlation between the band gap (Eg) and the doping sites of boron (B) atoms across various sizes of Si QDs. Additionally, a combination of Total Density of States (TDOS), Partial Density of States (PDOS) and orbital component analysis reveals that the subtle dipole effect near the B-doping site significantly contributes to the reduction in the band gap, providing valuable insights into the complex impact of different doping sites on the electronic arrangement and structure of Si QDs. Ultimately, our absorption spectroscopy, charge transfer and Quantum Theory of Atoms in Molecules (QTAIM) analysis of organic molecule coupling Si QDs reveal the formation of dipoles on the surface and the correlation between charge migration direction and binding sites. This phenomenon not only amplifies the presence of conjugated coupling states but also significantly enhances the charge transfer capability of Si QDs. These valuable insights will provide significant advantages to scientists and researchers endeavoring to tailor the electronic structure and optical attributes of Si QDs using a diverse array of modification techniques to meet specific application requirements. The surface functionalization of Si QDs involves doping or coupling site selection and the establishment of charge transfer bridges is crucial for the formation of dipole–dipole interaction which may not only play a role in regulating band gap structures but also exert significant control over the charge transfer capacity of Si QDs. [ABSTRACT FROM AUTHOR]

We present a theoretical investigation on the wide-band-gap semiconductor WO   3 in its room-temperature monoclinic structure. We carried out density functional theory and GGA-1/2 calculations on the bulk phase and the most stable (001) surface of the material, either in their stoichiometric form or in the presence of oxygen vacancies at various concentrations. Concerning the bulk phase, our results show how the inclusion of these defects correctly reproduces the intrinsic n-type doping of the material. The system is also found to be magnetic at reasonably high defect concentrations. As for the surface, the presence of vacancies gives rise to a magnetic behavior, whose features depend on the relative arrangement of native point defects. Oxygen vacancies are also responsible for additional tungsten oxidation states in both bulk and surface. Based on these results, we provide a rationale for the interpretation of most experimental data of this material and, possibly, other widespread transition metal oxides with similar properties and applications such as ReO   3 , TiO   2 , and SnO   2 . [ABSTRACT FROM AUTHOR]

The past decade witnessed substantial attention toward metal‐organic frameworks (MOFs) for photocatalytic water splitting owing to their versatile structural and optoelectronic characteristics. However, MOFs capable of efficient photocatalytic overall water splitting (OWS) remain notably scarce. Although MOF‐based photocatalysts with OWS potential are highly promising due to their diverse building blocks and topological configurations, the vast number of possible MOFs renders traditional trial‐and‐error materials discovery approaches impractical. Herein, a data‐driven methodology that integrates machine learning with high‐throughput first‐principles computations to identify MOFs with OWS capability is presented. By systematically assessing factors including water stability, band gap, band positions, charge carrier transport, and optical absorption properties, 14 MOFs from the Quantum‐MOF (QMOF) database containing over 20,000 MOFs as promising candidates for visible‐light‐driven OWS are identified. Notably, five of them exhibit exceptional electronic and optical properties, outperforming previously reported MOF OWS photocatalysts, such as UIO66(Zr)‐NH2, MIL125(Ti)‐NH2, and MIL53(Al)‐NH2 is established. This work represents a large‐scale, data‐driven exploration of MOF‐based photocatalysts for water splitting, shedding light on the untapped potential of photocatalysis in MOFs. [ABSTRACT FROM AUTHOR]

We conducted a large set of ab initio density functional theory computations to model a variety of hammer-terminated graphene nanoflakes—finite counterparts of armchair graphene nanoribbons. We focused on the relationships among the length and width of the nanoflakes, the stoichiometry and the conformation of the hydrogen saturation of the caps, and the resulting electronic structure. The energetics and the thermodynamic stability of the nanoflakes were investigated as well. Based on this study, we provide a recipe for determining the most stable saturation of the dangling bonds at the caps, which is generally disregarded in theoretical studies, and we prove that this step is crucial for a reliable description of the electronic structure of these systems. Data analysis proved that flakes far from the most stable C–H pattern exhibited electronic properties that were typical of an unsaturated bonding structure. Based on thermodynamics, we also proved that, for any given flake, there was a well-defined hydrogen content and a conformation of H atoms at the caps, which were favored across a wide range of environmental conditions. [ABSTRACT FROM AUTHOR]

The rational design of metal single‐atom catalysts (SACs) for electrochemical nitrogen reduction reaction (NRR) is challenging. Two‐dimensional metal–organic frameworks (2DMOFs) is a unique class of promising SACs. Up to now, the roles of individual metals, coordination atoms, and their synergy effect on the electroanalytic performance remain unclear. Therefore, in this work, a series of 2DMOFs with different metals and coordinating atoms are systematically investigated as electrocatalysts for ammonia synthesis using density functional theory calculations. For a specific metal, a proper metal‐intermediate atoms p‐d orbital hybridization interaction strength is found to be a key indicator for their NRR catalytic activities. The hybridization interaction strength can be quantitatively described with the p−/d‐ band center energy difference (∆d‐p), which is found to be a sufficient descriptor for both the p‐d hybridization strength and the NRR performance. The maximum free energy change (ΔGmax) and ∆d‐p have a volcanic relationship with OsC4(Se)4 located at the apex of the volcanic curve, showing the best NRR performance. The asymmetrical coordination environment could regulate the band structure subtly in terms of band overlap and positions. This work may shed new light on the application of orbital engineering in electrocatalytic NRR activity and especially promotes the rational design for SACs. [ABSTRACT FROM AUTHOR]

Novel semiconductor material with both high strength and ductility is urgently needed to meet the demands of increasing complex applications for electronic components. However, overcoming the inherent trade-off between strength and ductility has remained a longstanding challenge in materials science research. Herein, we proposed a three-dimensional carbon allotrope, oc-C24 with pure sp2 hybridization. This structure comprises arrays of carbon chains in an “8”-shape helix configuration, in between the C-chains which interlinked by the oriented ethylene with a planar π-conjugation. The distinctive structural unit imbues oc-C24 with remarkable tensile behavior, characterized by multi-stage chemical bond rearrangements and structural phase transitions along [010] crystallographic direction, displaying multi-level stress re-enhancement phenomena. A tensile strength of 104.2 GPa and a record strain of 1.05 are observed along [010] direction. Electronic band analysis reveals that oc-C24 is a semiconductor with an indirect band gap of 2.91 eV. The impressive tensile resistance and ductility of oc-C24 suggest its strong potential applications in electronic devices under extreme conditions. Our findings offer valuable insights and methodological strategies for designing novel carbon allotropes with unique mechanical responses.

Abstract The emergence of various topological semimetal states presents a novel opportunity for enhancing the efficiency of thermoelectric transport. This study introduces a recipe to improve the thermoelectric (TE) performance in topological materials containing single‐pair Weyl points (SP WPs) fermions and phonons. The recipe focuses on two key factors contributing to the enhancement of TE performance: the increase in the density of states to achieve a high power factor, and the introduction of additional phonon scattering to reduce the lattice thermal conductivity. The proposed recipe is confirmed in a half‐metallic SP WPs material BaNiIO6 through first‐principles methods. An enhanced density of states arises near the energy of the SP WPs in BaNiIO6, leading to a peak power factor connected to the complex Fermi surface due to the degeneracy of Weyl pockets in energy. Furthermore, it is shown that the SP WPs phonons in BaNiIO6 possess a high scattering rate and can likely contribute to the low lattice thermal conductivity, especially when two crossing points in SP WPs do not degenerate in frequency. The new recipe can be used for discovering high‐performance thermoelectric materials in the future by utilizing the transport advantages of degenerate‐in‐energy SP WPs fermions and non‐degenerate‐in‐frequency SP WPs phonons.