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The enhanced electronic properties and coupling effect of oxygen vacancies and Au single atoms promoted the activation of O 2 and the adsorption-oxidation of CO, which is responsible for the improvement of catalytic performance for CO-PROX. [Display omitted] • Oxygen vacancy-regulated atomic dispersed Au on CeFeO x catalyst for CO-PROX were prepared. • Nearly 100% CO conversion and 50% CO 2 selectivity were achieved at 80–150 ℃. • The electronic properties and the coupling of O v s and Au SAs promoted the CO-PROX. • O v s promoted the activation of O 2 and Au SAs preferred to adsorb CO instead of H 2. CO preferential oxidation in H 2 -rich stream (CO-PROX) is a critical reaction for H 2 purification in emerging hydrogen economy including advanced fuel cell technology. Au-based catalysts are viewed as some of the most promising catalysts but achieving high catalytic efficiency and selectivity is still challenging. Defect engineering is deemed as a powerful strategy to improve the intrinsic catalytic activity. Herein, CeFeO x -supported Au catalysts with controllable oxygen vacancy (O v) concentrations were obtained and applied to CO-PROX. The results of characterizations showed that the O v s were preferentially generated in conjunction with Au single atoms (SAs) rather than nanoparticles (NPs), which further modulated the surface electronic properties via surplus electrons in O v s and enhanced the interfical interaction between O v s and Au SAs. The CO-PROX results indicated that the reduced Au SA catalyst (Au 1 /CeFeO x -R) with the highest O v concentration completely converted CO at temperature of 80 °C with relatively low reactivity towards H 2 oxidation. The remarkable catalytic activity and selectivity were attributed to the modified electronic properties by O v s that played a bridging role in electron transfer and accelerated reaction process, as well as the coupling effect of O v s and Au SAs that enhanced the dissociative adsorption of O 2 and the adsorption-oxidation of CO, resulting in a reduced reaction energy barrier and making CO oxidation more favorable than H 2 oxidation. This research opens up an alternative strategy to simultaneously stabilize and activate single-atom catalysts. [ABSTRACT FROM AUTHOR]

The low-temperature‑carbonized carbon fiber (CF) with different diameters modified with silane coupling agent was prepared as the fillers and added into silicone resin (SR) composite coatings, in order to investigate the effects of the diameter and modification of fibers on the mechanical and electronic properties of the CF/SR composite coatings. The results of surface microscopy and structural analysis showed that more coupling agents were coated on the surface of thick fibers (TCFs) with a larger diameter, which provided more chemical bonds and mechanical meshing than fine fibers (FCFs) with a smaller diameter. The mechanical test and electrical test illustrated that the decrease in the diameter of fibers cannot only increase the mechanical properties of the composite coatings but also enhanced the surface resistivity with fewer amounts of fibers, which reduced the cost of the application. In particular, the surface resistivity of 2wt%TCF/SR was 11.60 MΩ/square, which was 455.02 % higher than that of 2wt%FCF/SR (2.09 MΩ/square). In addition, the silane coupling agent treatment also increased the mechanical properties and the surface resistivity of the composite coating. The surface resistivity of 2wt.%FCF-A/SR was 24.94 MΩ/square, while that of 2wt.%TCF-A/SR was 60.42 MΩ/square. Meanwhile, reducing the fiber diameter and the silane coupling agent treatment could increase the dielectric constant and dielectric loss of the coating, while could also meet the requirements in the wave transmission performance during the application of coatings. This paper illustrates that reasonable control of diameter and modification is required to improve the comprehensive performance of silicone composite coatings. It guides the application in the electrical magnetic interference field as well as the improved functionality of the composites. • The AMT modification of TCFs increased the roughness and provided more mechanical meshing for improving the interface bond than FCFs. • The reduction of fiber diameter and the modification improved the mechanical property attributed to the more crack deflection and interface adhesion. • The surface resistivity of FCF/SR was lower than that of TCF/SR because of the more conductive network. [ABSTRACT FROM AUTHOR]

Computed Phonon dispersion spectrum for KSrBi and KSrSb. [Display omitted] • The structural, mechanical, vibrational, electronic, thermodynamic and transport properties of the KSrY (X = Sb, Bi) Heusler compound were analyzed by DFT. • The Formation energy, vibrational properties and cohesive energy reveal that compounds are stable. • The thermoelectric characteristics are examined throughout a temperature range of 100 K to 1200 K and chemical potential. Currently, producing equipment and goods of all kinds that are economical, energy-efficient, and ecologically friendly is the main objective. In this study, an attempt has been made to look into these materials that meet these requirements. The structural, elastic, optoelectronic and transport characteristics of KSrY (Y = Sb,Bi) Half-Heusler were studied employing Full-potential, linearized augmented plane wave programs (FP_LAPW) approach as embedded in WIEN2K. The structural optimization was performed employing generalized gradient approximation (GGA). The computed lattice constants were reasonable in compliance with previous theoretical and experimental findings. The investigated KSrY (Y = Sb,Bi) were mechanically stable and brittle by nature. The KSrY (Y = Sb,Bi) compounds are discovered to have semiconducting nature with direct bandgap. The magnitudes of the bandgap for the KSrBi and KSrSb are 1.749 eV and 2.457 eV, respectively, using the mBJ approximation. The investigated materials on the basis of calculated band gap and optical spectra demonstrate the ability of the compounds to absorb both visible and UV light, henceforth application in optoelectronic devices. The Boltzmann transport theory included in the BoltzTraP package was used to study thermoelectric characteristics. The obtained figures of merit (ZT) values for the KSrY (Y = Bi, Sb) compounds are all close to unity at room temperature, suggesting optimum thermoelectric efficiency can be employed in thermoelectric devices. [ABSTRACT FROM AUTHOR]

The adjustable magnetic moments of REGe 6 − clusters increase monotonically. [Display omitted] • The dopant atoms are basically located at the top (or side) of pentagonal bipyramid. • The results of the theoretical study provide theoretical guidance for future experiments in anion photoelectron spectroscopy. • The adjustable magnetic moments of REGe 6 − (RE = Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu) clusters increase monotonically from 0 to 8µ B. • Most regions of the REGe 6 − clusters exhibit strong aromaticity. The geometries, electronic, and magnetic properties in a series of rare-earth (RE) metal atoms (Sc, Y, La, Ce, Pr, Nd, Pm, Sm, and Eu) doped Ge clusters, REGe 6 −, are investigated using density functional theory calculations and the results are compared with experimental literature data. It was found that all REGe 6 − clusters have similar pentagonal bipyramid structures, where the RE atom is located at the top (or side) of the pentagonal bipyramid. Natural population analysis reveals that the electrons always transfer from the RE atom to parent germanium atoms. The spin density and the density of states diagrams visually showed that the magnetic moments increase monotonically from Sc to Eu, which mainly derive from the contribution of the RE atoms. Isochemical shielding surfaces analyses indicate that the most regions of the REGe 6 − clusters (i.e., the pentagonal and the tetragonal ring in REGe 6 −) exhibit strong aromaticity compared with the benzene ring. [ABSTRACT FROM AUTHOR]

The π -bond Seiwatz chain (SC) is one of the well-known reconstruction induced by alkaline or rare earth metals on Si(111) surface. Here we identify by ab initio calculations a new reconstruction of La induced quasi-two-dimensional Si _3 trimer monolayer on Si(111)- $(\sqrt{3}\times \sqrt{3})R30{}^{\circ}$ surface. Its surface unit cell has one La atom and one Si _3 trimer with the same La coverage (1/3 monolayer) as SC structure and the Si _3 trimer satisfies the electron counting rule with a transfer of valence electrons from La atom, formally as ${\mathrm{L}\mathrm{a}}^{3+}{[{\mathrm{S}\mathrm{i}}^{-}]}_{3}$ , in correspondence to the milkstool model for Bi trimers on Si(111) surface. Band structure calculations show a semiconducting character with an indirect surface band gap of 0.76 eV. Moreover, a two-stage conversion process between the Si _3 trimer and SC structure is verified by the climbing-image nudged elastic band method. These findings pave the way for further exploration of the new surface structure and its outstanding properties.

Abstract Selective laser melting (SLM) using high laser power is a tendency in the future. In this paper, selective laser melting of Cu 10Zn alloy using high laser power of 1800 W has been performed. An optimal process parameters are obtained by studying the influence of process parametrs on the density of the SLMed samples. 99.97% relative density is achieved. Furthermore, the performances, such as microstructure, micro-hardness, mechanical properties and conductivity of Cu 10Zn parts using optimized parameters were investigated. The results show that the phase composition of SLMed Cu 10Zn is only α-Cu, the microstructure is elongated columnar grains which the size of building direction is much larger than that of other direction. A ;〈100;〉 crystallographic texture exists, which results an anisotropy on micro-hardness. Finally, the ultimate tensile strength of 269.2 MPa, yield stress of 203.4 MPa, elongation of 26.4% and conductivity of 43.19%ICAS are achieved for the SLMed Cu- 10Zn parts. Graphical abstract Unlabelled Image Highlights • Cu 10Zn gas-atomized powders were produced by high power selective laser melting. • SLMed Cu 10Zn requires higher laser power to be molten than steel or Al alloys. • A <1 0 0> crystallographic texture was observed on vertical section. • The tensile strength of 269.2 MPa and conductivity of 43.19%ICAS are achieved. [ABSTRACT FROM AUTHOR]

Abstract The stability, phase transition, magnetism and electronic properties of five different iron mononitride (FeN) phases are systematically studied using first-principles calculations. The results show that ZnS-FeN structure is the most stable phase at the equilibrium lattice, and the sequence of phase transition is according to ZnS→NiAs→wurtzite. Our magnetic analysis demonstrate that the ZnS, CsCl and wurtzite structures are nonmagnetic, while the NaCl and NiAs phases under high-pressure are magnetic, holding 2.27 and 1.61 μ B per Fe atom, respectively. The magnetic moments increase with increasing of the volume for all considered structures. Highlights • The properties of five FeN structures are studied using first principles calculations. • Enthalpy calculations show the sequence of phase transition is ZnS→NiAs→wurtzite • The transition pressures, from other four phases to the ZnS phase, are calculated. • The magnetic moments as a function of volume for all five structures are discussed. • The relations between the magnetic and electronic properties are analyzed. [ABSTRACT FROM AUTHOR]

Abstract Electronic and optical properties of armchair stanene nanoribbons are studied within the s p 3 tight-binding model including spin-orbit coupling in the presence of in-plane electric field. Electric field strongly modulates energy dispersions leading to a zero-gap transition, shift in edge-states, and exhibition of spin-splitting states. Then, the complex dielectric functions in the long wavelength limit is calculated from the gradient approximation. More field-induced transition channels exhibit richer optical spectra which further reveal spin-polarized feature at low frequency. Prominent plasmons in loss spectra come from π – σ mixing orbital. The plasmon peak frequency and height are tuned by field strength. Also, the threshold plasmon frequency linearly decreases as electric field increases and it vanishes at critical field. The reflectance exhibits oscillatory behaviors and shows dip structures with sharp plasmon edge, undergoing a red-shift with increasing field. The calculated results fully show that field-modulations of electronic and optical properties strongly depend on nanoribbon's geometry. Highlights • Electronic and optical properties of ASnNRs are studied by s p 3 TB-model with SOC. • Electric filed exhibits zero-gap transition, edge-state shift, and spin-split state. • Low-frequency optical absorption shows spin-polarization induced by F. • The threshold plasmon frequency linearly decreases with increasing F. • The reflectance exhibits a sharp dip structure undergoing a red-shift as F increases. [ABSTRACT FROM AUTHOR]

The structural, electronic, and magnetic properties of cobalt disulfide (CoS2) doped with oxygen (O), selenium (Se), or tellurium (Te) were investigated based on the spin-polarized first-principles calculations. Both the lattice constant and volume for CoO0.25S1.75 were smaller while those for CoSe0.25S1.75 and CoTe0.25S1.75 were larger than the corresponding values for CoS2. Both CoS2 and CoO0.25S1.75 were quasi-half-metallic, and both CoSe0.25S1.75 and CoTe0.25S1.75 were quasi-metallic. For CoS2, CoSe0.25S1.75, and CoTe0.25S1.75, the valence band maximums (VBMs) were contributed by Co-3d(t2g) states near the X-point, and the conduction band minimums (CBMs) were contributed by S-3p states at the Γ-point. For CoO0.25S1.75, the VBM was contributed by Co-3d(t2g) states at the M-point, and the CBM was contributed by Co-3d(eg) states near the R-point. Both O-S and Te-S dimers were strongly polarized, and the Se-S dimer was slightly polarized. CoS2 and CoX0.25S1.75 (X = O, Se, or Te) were magnetic, and Co atoms favoured ferromagnetic interaction. Except quasi-HM CoO0.25S1.75, quasi-metallic CoX0.25S1.75, CoX0.0625S1.9375, CoX0.03125S1.96875, and perfect metallic CoX0.25S1.75*, CoX0.125S1.875, were expected more suitable for use in supercapacitor and electrocatalyst. [ABSTRACT FROM AUTHOR]

Abstract The effects of the pressure on the structural, electronic, magnetic and optical properties of the Zn 0.75 V 0.25 Te alloy have been investigated by density functional calculations. The ductile characteristic and the half-metallic feature of Zn 0.75 V 0.25 Te alloy under pressure are found. The band structures with a color scale indicating the contribution weights from V and Te + Zn atoms show that V element is dominant in the spin-up channel crossing the Fermi level but there is a band gap in the spin-down channel. The half-metallic feature of the Zn 0.75 V 0.25 Te alloy can be observed under the pressures of 0–4 GPa. It is discovered that the total moment of 3 μ B /cell is contributed by the three 3d-electrons of V2 + ion. With increasing pressure, the spin-down band gap E g increases, while the static dielectric function ε 1 (0) and static refractive index n (0) decrease, the peaks of the real part ε 1 (ω) and imaginary part ε 2 (ω) of the dielectric constant, the refractive index n (ω) , the extinction coefficient k (ω) and absorption coefficient α (ω) all show the blue shift character. The results provide useful theoretical guidance for the application of the Zn 0.75 V 0.25 Te alloy in optical detectors and spintronics devices under pressure. Graphical abstract Image Highlights • The half-metallic feature of the Zn 0.75 V 0.25 Te under pressure is found. • The V element is dominant in the spin-up channel crossing the Fermi level. • The 3 μ B /cell total moment is contributed by the three 3d electrons of V2+ ion. • With increasing pressure, the E g increases, while ε 1 (0) and n (0) decrease. • The peaks of ε 1 (ω) , ε 2 (ω) , n (ω) , k (ω) and α (ω) all have blue shift character under pressure. [ABSTRACT FROM AUTHOR]

Abstract Despite the rapid progress in device efficiency of the perovskite solar cells (PVSCs), the origin of commonly observed large variability of device performance from one-step to two-step approaches is still elusive. Herein, the processing windows of perovskite films prepared by one-step and two-step processes have been investigated. We find that both perovskite films prepared by one-step and two-step methods in air are much rougher than that prepared in glovebox. For the one-step method, complete perovskite conversion can be readily achieved both in air and in glovebox, but totally different in surface morphology. For the two-step method, residual PbI 2 are remained in perovskite film, particularly with larger amount for the film prepared in air. Both rough surface and incomplete conversion hinder the realization of high quality perovskite film in air. The photovoltaic performances of the PVSCs prepared by one-step and two-step methods in glovebox are systematically compared. The generally observed lower photovoltaic performance of two-step PVSCs is ascribed to the additional trap-assisted recombination process due to larger trap density in the two-step perovskite film. This is confirmed by carrier recombination study using steady state photoluminescence, transient photovoltage and photocurrent measurements. Finally, combining the high work function hole transporting material poly-TPD, and the high-quality one-step perovskite film, a 17.5% high-efficiency PVSCs can be achieved. The results reveal the major impacts on the morphological and electronic properties of perovskite films between one-step and two-step method, and it brings insight into the strategy for extending the processing windows to achieve highly reliable PVSCs. Graphical abstract Image 1 Highlights • CH 3 NH 3 PbI 3 films fabricated by one-step and two-step solution process under different environments have been compared. • The processing window of one-step method is wider than that of two-step method, which is expected to be better for future large-scale production and commercialization. • Combining the high-quality one-step perovskite film with the high work function hole transporting material poly-TPD, a perovskite solar cell with high efficiency of 17.5% is achieved. [ABSTRACT FROM AUTHOR]

Abstract The adhesive work, interfacial energy, charge density, charge density difference and layer-projected density of states (DOS) of h-WC(0001)/γ-Fe (111) interfaces were calculated by the first principles method. The structural stability of the interfaces was researched by the adhesive work and interfacial energy of h-WC(0001)/γ-Fe (111) interfaces. The interfacial electronic structures were analyzed by charge density and charge density difference, and the interface bonding characteristics were revealed by Mulliken charges and layer-projected DOS of the interface models. The results show that the work of adhesion for C-terminated HCP stacking interface structure is the largest (W ad = 3.44 J/m2), which indicates that the reversible work used to separate the C-HCP interface into two free surfaces is the largest in all interfaces. When Δμ c changes from −0.37 eV to 0 eV, the interfacial energy of C-terminated HCP stacking interface structure is in the range of 1.186–1.588 J/m2, while that of W-terminated HCP stacking interface structure is in the range of 1.142–1.541 J/m2. When −0.165 eV < Δμ c < 0 eV, the interfacial energy of C-terminated HCP stacking interface is smaller than that of W-terminated one, which indicates the C-terminated HCP stacking interface is more stable. When −0.37 eV < Δμ c < -0.165 eV, W-terminated HCP stacking interface turns to be more stable than C-terminated one. The total charge density of C-terminated HCP stacking interface is much larger than that of W-terminated one, and the degree of ionization of C-terminated HCP interface is also higher. The bonding of C-terminated HCP stacking interface is a mixture of covalent bond, ionic bond and metallic one, while that of W-terminated HCP stacking interface is a mixture of covalent bond and metallic one. Graphical abstract Image 1 Highlights • Work of adhesion W ad and interfacial energy γ of h-WC(0001)/γ-Fe (111) interfaces were calculated. • Interfacial electronic structures between h-WC and γ-Fe were analyzed. • Interface bonding characteristics were revealed by Mulliken charges and layer-projected DOS. • The bonding strength between WC particle and various substrates was compared. [ABSTRACT FROM AUTHOR]

The structural, electronic and magnetic properties in bulk and various (0 0 1) surfaces of X 2 CoIn (X = Ti, Zr) Heusler alloy have been investigated by spin-polarized first-principles calculations. The InIn termination is the most stable one and the XIn termination is the second only to InIn termination as the most stable surface, with high spin polarizations 65.2% and 62.3% for X = Ti (80.8% and 69.6% for X = Zr), respectively. The atomic partial density of states (APDOS) and atomic magnetic moments (AMMs) of atoms in the central layer of X 2 CoIn (0 0 1) surface accord well with those of the corresponding atoms in bulk X 2 CoIn structure. The half-metallic (HM) feature is destroyed by the surface states for all the five CoCo, XCo, XX, XIn and InIn terminations. The total magnetic moment is contributed by atoms in all layers for Ti 2 CoIn (0 0 1) surface while is mainly contributed by the atoms in the fourth to central layers (L 4 to L 9 ) for the ZrIn termination but is mainly contributed by the atoms in the sixth to central layers (L 6 to L 9 ) for the InIn termination for Zr 2 CoIn (0 0 1) surface. Further experimental efforts are expected to fabricate the X 2 CoIn thin films and investigate the structural, electronic and magnetic properties of them. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Au or Cl adsorption on the 1I-terminated BiOI (0 0 1) surface is investigated. • Au/BiOI and Cl/BiOI systems possess the better utilization of the visible light. • Au-H system shows the best photocatalytic performance and structural stability. Abstract First-principles calculation based on DFT is performed to explore the structural, electronic and optical properties of monatomic Au or Cl adsorption on the bridge and fourfold hollow site of the 1I-terminated BiOI (0 0 1) surface. The results indicate that Au/BiOI and Cl/BiOI adsorption systems not only possess the better structural stability but also exhibit the perfect utilization of the visible light. The range of visible light utilization is broadened after Au or Cl adsorption at the B and H sites thus the photocatalytic performance can be improved. Au adsorption at H site shows the best photocatalytic performance and structural stability. [ABSTRACT FROM AUTHOR]

First-principle calculations based on the density functional theory (DFT) with the GGA approximation are done to study the electronic and optical properties of MoS2 and MoS2:V graphene-like(GL) cases. In the pure case, the MoS2 GL has the direct energy gap value of 1.7eV. By absorbing the Vanadium (V) impurity to MoS2 GL structure, its electronic property is changed to Half-metallic behavior, and also the energy gap of MoS2:V GL is reduced to 1.6eV amount in up spin. The MoS2 GL absorption is started in the visible area while a small absorption is occurred in the infrared region at x-direction by adding V impurity, and the real and imaginary parts of the dielectric functions claim to have metallic treatment in the mentioned direction. [ABSTRACT FROM AUTHOR]

Abstract First-principles calculations based on density functional theory are carried out to investigate the formation energy, transition energy level, electronic structure and effect of strain on Ce-doped SnS 2 monolayer nanosheet. Numerical results show that the doped nanocompound is energetically stable, while the introduced dopant state is composed completely of Ce_4f electrons, and the adopted perfect SnS 2 monolayer leads to the disagreement with experimental Ce3+ ionic state. Applying biaxial strain from −10% to +10%, the doped system holds the indirect semiconducting characteristics in the strain range −4%∼+6%. The variation tendency of bandgaps is almost to be a horizontal line about 1.9eV under compressive conditions, and the bandgaps increase slowly at first and then decrease rapidly beyond +4%. This work is useful for further improving Ce-doped SnS 2 nanostructures and paves the way in the potential application in photocatalysis and lithium-ion battery. [ABSTRACT FROM AUTHOR]

We investigated the electronic and magnetic properties of bulk and monolayer CrSi2 using first-principle methods based on spin-polarized density functional theory. The phonon dispersion, electronic structures, and magnetism of bulk and monolayer CrSi2 were scientifically studied. Calculated phonon dispersion curves indicated that both bulk and monolayer CrSi2 were structurally stable. Our calculations revealed that bulk CrSi2 was an indirect gap nonmagnetic semiconductor, with 0.376 eV band gap. However, monolayer CrSi2 had metallic and ferromagnetic (FM) characters. Both surface and confinement effects played an important role in the metallic behavior of monolayer CrSi2. In addition, we also calculated the magnetic moment of unit cell of 2D multilayer CrSi2 nanosheets with different layers. The results showed that magnetism of CrSi2 nanosheets was attributed to band energy between layers, quantum size, and surface effects. [ABSTRACT FROM AUTHOR]

Surface functionalization can be used to tune the electronic and mechanical properties of MXenes. In this work, the structural stability, electronic and mechanical properties of monolayer M 2 X (M = Sc, Ti, V, Mn, Nb, Mo, Hf; X = C, N) with asymmetrical functionalization to form Janus MXenes were investigated by first-principles calculations, and the results were compared with the symmetrical functionalization. Results show that asymmetric functionalization has a consequential effect on the structure stability, electronic, elastic properties of the MXenes. For pristine monolayer M 2 X (M = Sc, Ti, V, Mn, Nb, Hf; X = C, N) systems, T-phase is energetically stable than H-phase, whereas the stable structures of monolayers Mo 2 C and Mo 2 N are H-phase. All the asymmetrically functionalized monolayers M 2 X (M = Sc, Ti, V, Mn, Mo, X = C, N) except for Sc 2 C are metallic materials. A metallic to semiconductor transition occurs in monolayer Sc 2 C upon surface functionalization. The mechanical stability of monolayer M 2 X can be improved by Janus surface functionalization. [ABSTRACT FROM AUTHOR]

Structure, stability and electronic properties of Pt m Ir n ( m  +  n  = 2–7) clusters have been systematically investigated by using density functional theory (DFT) with considering the generalized gradient approximation (GGA). The results reveal that the ground state structures change from planar to three-dimensional structures with the increase of the number of atoms, and Ir atoms play a decisive role in the formation of Pt m Ir n clusters. The addition of a small amount amount of Ir improves the stability of pure Pt clusters. The stability analysis indicates that most of the Pt-rich clusters are more stable than those of the Ir-rich with same cluster size. The PtIr cluster charge transfer analysis illustrates that it not only occurs in different orbits, but also occurs between different atoms. PtIr 3 , Pt 4 Ir, Pt 4 Ir 2 , Pt 3 Ir 3 , Pt 2 Ir 4 , PtIr 5 and Ir 7 clusters exhibit comparatively large magnetism. [ABSTRACT FROM AUTHOR]

Geometric and electronic structures of W m Cu n H2 (m + n ≤ 7) clusters have been systematically calculated by density functional theory (DFT) at the generalized gradient approximation (GGA) level for ground-state structures. For all W–Cu clusters, H atoms prefer to attach to W atoms in this system during adsorption. And more electrons transfer from H atom to W atom with the growth of the size of the cluster which benefits the hydrogen storage. Analysis of stability properties and electronic properties shows that hydrogen adsorption and dissociation process take place more efficiently at the W2Cu3H2 cluster than the others. Due to high thermodynamic stability and adsorption energy of W5CuH2 cluster among W m Cu n H2 (m + n ≤ 7) clusters, W5Cu is more suitable for hydrogen storage. [ABSTRACT FROM AUTHOR]

Abstract Penta-graphene has been widely studied recently due to its superior properties for promising applications. We here theoretically investigate electronic property and carrier mobility for four kinds of penta-graphene nanoribbons (P-GNRs) terminated with nonmetallic atom (H, N, P, O, S and F) at two edges (one part of P-GNR surface). The calculations show that these ribbon possess a favorable energetic stability and thermal stability. Interestingly, three kinds of ribbons (ZZ-, ZA-, and AA-types) with these terminations have a basically similar electronic structure, only with terminations O and S, they can be semiconductors, whereas other are metals or quasi-metals. The remaining ribbon (SS-type) can maintained to be semiconductors for all types of termination situations. These behaviors are intimately related to the suppression of the edge states of edge C atoms due to the coupling effects of termination atoms. In particular, these ribbons also hold a rich carrier mobility feature from ∼101 to ∼104 cm2 V−1 s−1 at room temperature depending on termination atoms. The S atom termination can lead to a significant carrier polarity for all the ribbons, and size effects of ribbons on carrier mobility also is clearly observed as well. These findings suggests that the functionalized P-GNRs might hold promising potential applications in nanoelectronic devices. Graphical abstract Image 1 Highlights • Electronics and carrier mobility of edge-modified penta-graphene nanoribbons are studied. • Such ribbons show metallic or semiconducting behaviors depending on termination atoms. • Edge-modifications can regulate carrier mobility significantly. [ABSTRACT FROM AUTHOR]

Using first-principles calculations, the electronic properties of SiSe monolayer under in-plane strains are studied. It is found that the band gap of SiSe monolayer is increased linearly under the tensile strains along armchair direction. The tensile strain of 7% along zigzag direction makes a transition of band gap from indirect to direct. Under the biaxial compressive strains from 0% to −5%, we found that the band gap of SiSe monolayer is decreased continuously. Moreover, the SiSe monolayer exhibits metallic behavior under the −5% biaxial compressive strain. [ABSTRACT FROM AUTHOR]

Utilizing the crystal structure prediction method (CALYPSO), a tetragonal B C O compound ( t I12 - B 6 C 4 O 2 with I 4 ¯ m2 symmetric structure) was predicted. Computed formation enthalpies, elastic constants and phonon dispersion spectra certify that t I12-B 6 C 4 O 2 is thermodynamically, dynamically and mechanically stable. Our results indicate that t I12 - B 6 C 4 O 2 has large mechanical moduli and high hardness (21.9 GPa). The directional dependences of the Young’s modulus, shear modulus and Poisson’s ratio have been visualized to analysis the mechanical anisotropy. The calculated band structure and partial density of state revealed that t I12 - B 6 C 4 O 2 is a typical for conductor with sp 3 hybrid B C and B O covalent bonds. [ABSTRACT FROM AUTHOR]

Using density functional theory (DFT), we have studied the structure of a zigzag silicene nanoribbons (SiNRs) with periodically embedded with four- and eight-membered rings, and studied their electronic properties by calculating its band structures and density of states (DOS). The results showed that the zigzag SiNRs have a sp 2 hybridization, in addition, the band gap gradually decreased with the increase of the width by layer, and gradually changed from semiconductor properties to metal properties. The existence of vacancy defects increased the band gap and energies, but their positions could not change the structure and the electronic properties. [ABSTRACT FROM AUTHOR]

The structural, electronic, magnetic and optical properties of the yttrium-based binary Heusler alloy Y 3 Si , ternary Heusler alloy Y 2 CrSi and quaternary Heusler alloy ScYCrSi have been studied by first-principles calculations. The results show that the preferred configurations of Y 3 Si , Y 2 CrSi and ScYCrSi alloys are DO 3 - FM , Hg 2 CuTi − FM and YI − FM configurations, respectively. The Y 3 Si alloy is a conventional metal ferromagnet. While the Y 2 CrSi and ScYCrSi alloys are HM ferromagnets with spin-up band gaps of 0.682 eV and 0.862 eV as well as the HM characters are maintained in the lattice constant ranges of 6.365–7.057 Å and 6.029–7.129 Å, respectively, ensuring potential applications in spintronics. The total magnetic moments of the Y 2 CrSi and ScYCrSi alloys are all 2 μ B /f .u . , satisfying the Slater-Pauling rule M t = 18 - Z t . Among three alloys considered, the Y 2 CrSi alloy has the lowest static dielectric constant, static reflective index, static refractive index, global maximum energy loss function but the highest maximum imaginary part. The phonon dispersion spectra show both Y 2 CrSi and ScYCrSi alloys are dynamically stable, while the Y 3 Si alloy is dynamically unstable. [ABSTRACT FROM AUTHOR]

KCdCO 3 F is a newly synthesized promising ultraviolet nonlinear optical crystal, but its structure is disputed and its fundamental properties have not been well studied. Here our first-principles study indicates that the structure with the space group P 6 ¯ c 2 is energetically more stable than the P 6 ¯ m 2 phase. We systematically investigated its electronic, optical, vibrational, infrared, and elastic properties. The results reveal that KCdCO 3 F is a direct-band-gap insulator with rather flat bands below the Fermi level. Analyses of its partial density of states revealed that the top (bottom) of its valence (conduction) band is formed by the O 2p (Cd 5s) orbital. It is a negative uniaxial crystal with ionic-covalent nature. Both infrared-active and Raman-active modes exist at its Brillouin zone center, and ions contribute more to its static dielectric constants. Its optical spectra in the visual and infrared ranges were studied, and their origins were revealed. Calculations indicate that KCdCO 3 F is mechanically stable but anisotropic since it is more vulnerable to shear stress and is easy to cleave along the c axis. [ABSTRACT FROM AUTHOR]

The structural, electronic and magnetic properties of CoS 2 under pressure have been investigated by the first-principles calculations. The lattice constant and volume decrease with increasing pressure. The CoS 2 is stable and behaves a brittle characteristic under the pressures of 0–5 GPa. The CoS 2 presents metallic characteristic under the pressures of 1–5 GPa although it is nearly half-metal (HM) under the pressure of 0 GPa. The lowest conduction bands for spin-up and spin-down channels shift towards higher and lower energy region, respectively, with the pressure increasing from 0 to 5 GPa. In spin-up channel the conduction band minimum (CBM) is mainly contributed by Co-3d(e g ) orbitals at R point but the valence band maximum (VBM) is contributed by Co-3d(t 2g ) orbitals near M point. While in spin-down channel the CBM is contributed by S-3p orbitals at Γ point but the VBM is contributed by Co-3d(t 2g ) orbitals near X point. The CoS 2 is still suitable to be used in the supercapacitor under the environmental pressures of 0–5 GPa due to the high conductivity. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C 3 N 4 ) is an attractive photocatalyst which has appealing visible light absorption, outstanding layered porous structure, high stability and nontoxicity. Many experimental methods have been developed to modify the pristine g-C 3 N 4 and enhanced photocatalytic activities have been witnessed. First-principle calculation based on density functional theory is an effective approach to investigate the structural, electronic, optical and thermodynamic properties of molecules and crystals, which provides important information to elucidate the improved photocatalytic activity of modified g-C 3 N 4 at atomic or unit-cell levels, or even further, to predict the property and photocatalytic activity of experimentally un-synthesized g-C 3 N 4 -based photocatalysts. This review is dedicated to this important material, i.e. tri- s -triazine-based g-C 3 N 4 and summarized a panorama of the major advances in the first-principle investigation. The existing challenges and future directions at the forefront of this emerging research hotpot have also been discussed. [ABSTRACT FROM AUTHOR]

Two stable forms of copper oxides namely, CuO and Cu 2 O are potential materials for optoelectronic application, particularly for photovoltaics, due to their large absorption coefficient (α ∼ 10 5  cm −1 ) and broad absorption spectra covering a wide spectral range (from UV to NIR). Additionally, these materials are environmentally benign, stable and are available at low cost. Oxides of copper, therefore have been explored for their possible application in variety of directions including photovoltaics and gas-sensing. Here we developed an easy and environment friendly synthesis protocol for nanoparticles of both types of copper oxide and investigated in detail their structural, optical and electronic property. Synthesized materials were characterized using X-ray diffraction, SEM, TEM, FTIR-spectroscopy and UV–Vis reflectance measurements. Theoretical modeling tool based on density functional theory (DFT) has been used for deeper understanding of the semiconducting nature of these materials. For detail characterization, the as-synthesized nanoparticles of Cu 2 O was used without further annealing treatment and consequently was found to have smaller sized crystalline grains and higher degree disorder as compared to CuO. Electronic structure calculations confirmed the semiconducting nature for both the oxides with the occurrence of direct bandgap. These results are promising as they demonstrate an easy synthesis protocol to obtain crystalline nanoparticles of CuO. The crystallinity of Cu 2 O obtained in this study is inferior and can be improved via further annealing in inert atmosphere. [ABSTRACT FROM AUTHOR]

The geometries, electrical characters and reaction paths from Fe(CO)5molecule to small Fe clusters were investigated by using all-electron density functional theory. The results show that in the decomposition process of pentacarbonyl-iron, Fe(CO)5molecule prefers to remove a carbon monoxide and adsorb another Fe(CO)5molecule to produce nonacarbonyldiiron Fe2(CO)9then Fe2(CO)9gradually removes carbon monoxide to produce small Fe clusters. As It can be seen from the highest occupied molecule orbital–lowest unoccupied molecule orbital gap curves, the Fe(CO)n=3, and 5and Fe2(CO)n=3, 7 and 9intermediates have higher chemical stability than their neighbors. The local magnetic moment of the carbon monoxide is aligning anti-ferromagnetic. The effect of external magnetic field to the initial decomposition products of Fe(CO)5can be ignored. [ABSTRACT FROM AUTHOR]

The geometries, stabilities and electronic properties of AlnPdm (n = 1{10, m = 1; 2) have been systematically investigated by using the DFT method at B3PW91/GENECP level. The optimized results indicate that the lowest-energy structures of AlnPd clusters prefer to form three-dimensional (3D) structures and the Pd atom occupies a peripheral position of AlnPd clusters. The most stable AlnPd2 clusters can be obtained by adding one Al atom to the most stable structure of Aln-1Pd2 clusters except for n = 7 and 10. The two Pd atoms are found to occupy the exclusive surface sites. The analysis of stabilities reveals that Al3Pdm and Al7Pdm clusters are more stable than their neigh- bors. The doping of Pd atoms enhances the stabilities of aluminum clusters. The charges always transfer from Al atoms to Pd atoms in AlnPdm clusters. There exists strong spd orbital hybridization between Pd and Al. The results of polarizability imply that the nucleus and electron cloud of these clusters are easily affected by the external field and the nonlinear optical effect of AlnPd and AlnPd2 clusters is enhanced with the increase of cluster size. [ABSTRACT FROM AUTHOR]

The TiN(111)/ZrN(111) interface was studied by first‐principles method to provide the theoretical basis for developing the TiN/ZrN coatings. Twelve geometry structures of TiN(111)/ZrN(111) interfaces were established. The calculated interfacial work of adhesion reveals that the N‐terminated TiN/N‐terminated ZrN interface with TL site shows the strongest stability. For this TiN(111)/ZrN(111) interface, the results of the partial density of state indicate that the chemical bonding at the interface appeals both ionic and covalent characteristic, which is same as that in the bulk materials. The partial density of states for Zr, Ti, and N atoms at the interface are very similar with those in the bulk, which reveals that the electronic structure transition at the interface is smooth. The results of charge density and charge density difference demonstrate that the lost charge of Ti atom is larger than that of Zr atom, indicating that TiN is more ionic than ZrN. Calculations of the work of fracture indicate that the mechanical failure of the ZrN(111)/TiN(111) interface will take place at the interface. Besides that, the calculation result of the TiN(111)/ZrN(111) interface implies that the TiZrN2 phase might be formed at the interface because the contacting of the N―N bond is the most stable. [ABSTRACT FROM AUTHOR]

Vegetable insulating oil may replace the mineral insulating oil used in large power transformers due to its extraordinary biodegradability and fire resistance. According to component analysis, 1-methylnaphthalene and eicosane are considered the typical molecules in mineral oil. Triolein and tristearin are considered the typical molecules in vegetable oil. The ionization potential (IP) and the variation of highest occupied molecular orbital (HOMO) of typical molecules under an external electric field are calculated using quantum chemistry methods. The calculation results show that the IP of the triolein molecule is comparable to that of the 1-methylnaphthalene molecule. The mechanisms of losing electrons are discussed, based on the analysis of HOMO composition. The insulation characteristics of the triolein and tristearin are more likely to be degraded under an external electric field than those of 1-methylnaphthalene and eicosane. Due to the fact that the number density of low IP molecules groups in vegetable oil is much greater than that in mineral oil, the polarity effect in vegetable oil is more obvious than that in mineral oil. This eventually leads to different streamer characteristics in vegetable oil and mineral oil under positive polarity and negative polarity. [ABSTRACT FROM AUTHOR]

A first principles study of the electronic and optical properties of the Vanadium impurity on the Ti 3 C 2 graphene like has been done in the framework of density functional theory to calculate the density of states, Bandstructure and optical coefficients spectra. Results inferred to the metallic behavior for Ti 3 C 2 :V graphene like. Adding the V impurity caused the energy loss has a red shift and the dielectric function show lower metallic behavior and the reflection index is shifted to one in the lower energy. Also, for the two cases we have anisotropy for the x and z direction. [ABSTRACT FROM AUTHOR]

Geometric and electronic structures of WMo ( m + n 7) clusters have been systematically calculated by density functional theory (DFT) at the generalized gradient approximation (GGA) level for ground-state structures. Geometry optimization shows that clusters are almost bipyramid structures with m + n 4. E of clusters is mainly dominated by W atoms. And the substitution of atoms between W and Mo in Mo or W ( n 7) clusters enhances the stability of the original clusters. The calculated IE shows that WMo, WMo2, WMo3 and WMo are relatively more stable in the chemical reaction. In addition, the magnetism of clusters mainly comes from valance d orbitals. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid halide perovskite CH 3 NH 3 PbI 3 (MAPbI 3 ) has received rapid progress in power conversion efficiency as promising photovoltaic materials, yet the surface structures and the role of MA cations are not well understood. In this work, we investigated the structural stability and electronic properties of (001) surface of cubic, (001) and (110) surfaces of tetragonal and orthorhombic phases of MAPbI 3 with considering the orientation of MA cations, by density functional theory calculations. We demonstrate that the orientation of MA cations has profound consequences on the structural stability and the electronic properties of the surfaces, in contrast to the bulk phases. Compared with the MA-I terminated surfaces, the Pb-I 2 terminated ones generally have smaller band gaps and the advantage to enable the photo-excited holes to transfer to the hole-transport materials in both tetragonal and orthorhombic phases. Overall, we suggest that the films with Pb-I 2 terminated surfaces would prevail in high performance solar energy absorbers. [ABSTRACT FROM AUTHOR]

Monolayer molybdenum disulfide (MoS2) has obtained much attention recently and is expected to be widely used in flexible electronic devices. Due to inevitable bending in flexible electronic devices, the structural and electronic properties would be influenced by tensile strains. Based on the density functional theory (DFT), the structural and electronic properties of monolayer MoS2 with a sulfur (S)-vacancy is investigated by using first-principles calculations under uniaxial tensile strain loading. According to the calculations of vacancy formation energy, two types of S-vacancies, including one-sulfur and two-sulfur vacancies, are discussed in this paper. Structural analysis results indicate that the existence of S-vacancies will lead to a slightly inward relaxation of the structure, which is also verified by exploring the change of charge density of the Mo layer and the decrease of Young's modulus, as well as the ultimate strength of monolayer MoS2. Through uniaxial tensile strain loading, the simulation results show that the band gap of monolayer MoS2 decreases with increased strain despite the sulfur vacancy type and the uniaxial tensile orientation. Based on the electronic analysis, the band gap change can be attributed to the π bond-like interaction between the interlayers, which is very sensitive to the tensile strain. In addition, the strain-induced density of states (DOS) of the Mo-d orbital and the S-p orbital are analyzed to explain the strain effect on the band gap. [ABSTRACT FROM AUTHOR]

InSe/WS 2 heterostructure (HS) was constructed in this study to combine the excellent properties of these two monolayer semiconductors. The calculation of enthalpy of formation, phonon spectrum, and elastic constants of heterostructure based on first-principle proves that InSe/WS 2 HS has good stability and mechanical property. The study of electronic properties illustrates that InSe/WS 2 HS is a type II direct band gap semiconductor with photogenerated electrons (holes) located mainly on the InSe (WS 2)-layer, the electron mobility of heterostructure increased a lot (4357.65 cm2V−1s−1), and the hole mobility enhanced a little after the combination of the heterostructure. In addition, the band gap is greatly reduced, providing it with a stronger light absorption capability. Likewise, optical properties (absorption coefficient, reflectivity, loss function, refractive index, dielectric function, and photoconductivity) can be modulated under applied biaxial strain. More importantly, the band gap can be significantly tuned under applied strain (direct ⇆ indirect, 0.02 eV ∼ 1.5eV) to meet the different requirements of devices for semiconductor devices. • The InSe/WS 2 HS's structural stability was proved adequately through the phonon spectra, negative binding energy. • The modulation of mechanical, electronic, and optical properties of InSe/MoSe 2 HS under biaxial strain was investigated. • The InSe/WS 2 HS of narrow direct type-Ⅱ band gap semiconductor exhibits n-type semiconductor characteristics. • The band gap type transitions from direct band gap to indirect band gap at 4% compressive strain. [ABSTRACT FROM AUTHOR]

Solid molecular hydrogen exhibits a rich variety of unique properties, including insulator-to-metal transition. However, the specific structure of phase III remains unclear. Experimental evidence suggests high-pressure hydrogen shows a hexagonal close-packed lattice. Therefore, as a potential candidate for phase III, the structure, energetic, mechanical, electronic, and thermodynamic properties of P 6 1 22 structure are systemically studied. It is found phase III with P 6 1 22 space group is both mechanically and thermodynamically stable within the pressure range of 120∼300 GPa. Besides, we observed significant enhancements in the bulk modulus, shear modulus, and Young's modulus. The band structures exhibit a transition from topological insulator to topological semiconductor and eventually to a Wely semimetal as the pressure increases. The electron density accumulates between pseudo "H 2 " molecules in the insulating phase but it partly channels into the interlayer space in the semimetallic phase. Phase III with P 6 1 22 structure is barely explored previously in solid hydrogen, therefore, we believe our present investigation contributes valuable insights towards understanding the behavior of metallic hydrogen. • Solid hydrogen in P 6122 phase is mechanically and thermodynamically stable in the pressure range of 120∼300 GPa. • The bulk modulus B , shear modulus G and Young's modulus E increase linearly as pressure increases. • Topological insulator to semi to Weyl semimetal transition: 120-300 GPa. • Electron density shifts from the intra-layer of the insulator state to the inter-layer of the semimetal state. [ABSTRACT FROM AUTHOR]

[Display omitted] • Covalent functionalization of phenyl resulted in a semiconductor–metal transition for black phosphorus. • Strains applied along the armchair direction restored the phenyl-functionalized black phosphorus to a p-type semiconductor. • It existed prominent bonding states between the interlayer broken P atoms under tensile strain. • The compressive strain heightened the adsorption capacity and reflectivity of phenyl-functionalized black phosphorus in high-energy regions. The electronic and optical properties of phenyl-functionalized black phosphorus (phenyl-BP) under uniaxial strain engineering were investigated using first-principles calculations. It revealed that the overall transitions from semiconductor to metallic properties were observed in the phenyl-BP. Notably, when 4% tensile strain was exerted along the armchair direction, phenyl-BP was restored to a p-type semiconductor with a smaller gap of 0.60 eV. Furthermore, compressive strain enhanced its ability to absorb ultraviolet light and high photon energy region around 14 eV. Our results suggested that the strain-induced properties of phenyl-BP provided a theoretical guidance for realizing its full potential in optoelectronic applications. [ABSTRACT FROM AUTHOR]

The structural, electronic, and spectral properties of Al n Cu k (n = 1–16; k = 0, ±1) clusters have been examined via ab initio calculations combined with the CALYPSO method. It is found that the Cu atom in the ground-state Al n Cu k cluster is situated on the surface for n = 1–11 and prefers a central site for n = 12–16 (except for in Al 15 Cu, Al 12 Cu+, and Al 16 Cu+). The stability, chemical activity, ionization potential, and electron affinity of the Al n Cu k clusters are closely linked to the cluster size, the number of valence electrons, the point group, and the spin state. Simultaneously, we simulated UV spectra, photoelectron spectra, and vibrational and Raman spectra of the Al n Cu k clusters. The global minimum structure of the A l n Cu− cluster is recognized by our comparing the simulated and measured photoelectron spectra. The spectra and orbital of Al 13 Cu alloy cluster. [Display omitted] • The dopant Cu atom in big aluminum clusters tends to occupy the most highly coordinated location. • The closed-shell structures are able to significantly enhance the stability of the Al n Cuk clusters. • The symmetry of Cu-doped aluminum cluster has a large influence on its chemical activity. • The major dissociation products of Al n Cu + cluster is Al+(or Al) and Al n-1 Cu (or Al n-1 Cu+). [ABSTRACT FROM AUTHOR]

Non-bonding-type dual-metal atom sites have emerged as a frontier for bifunctional electrocatalysis, however, respectively customizing the local electronic states of two metal sites remains elusive. Herein, by fabricating FeN 4 and NiN 4 single atoms that Janus-distributed on the inner and outer of sulfur-doped carbon hollow spheres, namely FeN 4 -SC-NiN 4 , we demonstrate the sulfur-induced anisotropic electronic regulation for Fe/Ni dual-atom sites and build "one stone two birds" bidirectional facilitation mechanism for reversible oxygen electrocatalysis. For the separated FeN 4 and NiN 4 sites, the ambient sulfur reduces the charges of FeN 4 sites while downshifts the d -band center of NiN 4 sites. Such enlarged difference in electronic structure respectively promotes OH* desorption at FeN 4 sites but accelerates O 2 * stripping at NiN 4 sites, enabling the FeN 4 -SC-NiN 4 dual-atom sites to feature simultaneously enhanced oxygen reduction (E 1/2 =0.844 V) and oxygen evolution (η 10 =246 mV iR-free) activity, together with a small potential gap (0.632 V) and superior long-term cycling stability for Zn-air battery. [Display omitted] • The FeN 4 -SC-NiN 4 with Janus-distributed FeN 4 and NiN 4 atomic sites was fabricated. • The FeN 4 -SC-NiN 4 catalysts show both high ORR and OER activity for Zn-air battery. • The "one stone two birds" bidirectional regulation of sulfur is verified for ORR/OER. [ABSTRACT FROM AUTHOR]

The realistic InSb nanostructures namely InSb nanoring, InSb nanocube, InSb nanocube-18, InSb nanosheet, InSb nanocage and InSb nanocube-27 are simulated and optimized successfully using B3LYP/LanL2DZ basis set. The stability of InSb nanostructures is studied in terms of binding energy, vibrational studies and calculated energy. The electronic properties of InSb nanostructures are discussed using ionization potential, electron affinity and HOMO–LUMO gap. Point symmetry and dipole moment of InSb nanostructures are reported. Incorporation of impurity atom in InSb nanostructures is studied using embedding energy. The present study provides the information regarding the enhanced electronic properties of InSb nanostructure which finds its potential importance in microelectronics and optoelectronic devices.