Loading Stress Analysis of Cement Concrete Pavement in Mountainous Areas

The suitable cement concrete pavement for mountainous areas is a form of low-cost cement concrete pavement that uses unconventional graded stones in different proportions in ordinary concrete,allowing the concrete to fully contact the stones and form a stable and well-bonded slab with large particle stones.As large particle stones replace a certain volume of cement concrete,they have good economic performance and are a low-cost form of cement concrete pavement.This study researches the use of ANSYS tools to analyze the influence of geometric dimensions and material properties of rigid pavement structural layers on the mechanical properties of pavement structures.

Growth behaviors and emission properties of Co-deposited MAPbI_(3) ultrathin films on MoS_(2)

Hybrid organic–inorganic perovskite thin films have attracted much attention in optoelectronic and information fields because of their intriguing properties. Due to quantum confinement effects, ultrathin films in nm scale usually show special properties. Here, we report on the growth of methylammonium lead iodide(MAPbI_(3)) ultrathin films via co-deposition of PbI_2 and CH_3NH_3I(MAI) on chemical-vapor-deposition-grown monolayer MoS_(2) as well as the corresponding photoluminescence(PL) properties at different growing stages. Atomic force microscopy and scanning electron microscopy measurements reveal the MoS_(2) tuned growth of MAPbI_(3) in a Stranski–Krastanov mode. PL and Kelvin probe force microscopy results confirm that MAPbI_(3) /MoS_(2) heterostructures have a type-Ⅱ energy level alignment at the interface. Temperaturedependent PL measurements on layered MAPbI_(3) (at the initial stage) and on MAPbI_(3) crystals in averaged size of 500 nm(at the later stage) show rather different temperature dependence as well as the phase transitions from tetragonal to orthorhombic at 120 and 150 K, respectively. Our findings are useful in fabricating MAPbI_(3) /transition-metal dichalcogenide based innovative devices for wider optoelectronic applications.

Recent progress in 2D group-V elemental monolayers:fabrications and properties

A large number of two-dimensional(2D)monoelemental materials with huge application potentials have been developed,since graphene was reported as a monoelemental material with unique properties.As cousins of graphene,2D group-V elemental monolayers have gained tremendous interest due to their electronic properties with significant fundamental bandgap.In this review,we extensively summarize the latest theoretical and experimental progress in group-V monoelemental materials,including the latest fabrication methods,the properties and potential applications of these 2D monoelementals.We also give a perspective of the challenges and opportunities of 2D monoelemental group-V monolayer materials and related functional nanodevices.

Progress on 2D topological insulators and potential applications in electronic devices

Two-dimensional topological insulators(2DTIs)have attracted increasing attention during the past few years.New 2DTIs with increasing larger spin-orbit coupling(SOC)gaps have been predicted by theoretical calculations and some of them have been synthesized experimentally.In this review,the 2DTIs,ranging from single element graphene-like materials to bi-elemental transition metal chalcogenides(TMDs)and to multi-elemental materials,with different thicknesses,structures,and phases,have been summarized and discussed.The topological properties(especially the quantum spin Hall effect and Dirac fermion feature)and potential applications have been summarized.This review also points out the challenge and opportunities for future 2DTI study,especially on the device applications based on the topological properties.

Band engineering of double-wall Mo-based hybrid nanotubes

Hybrid transition-metal dichalcogenides （TMDs） with different chalcogens on each side （X-TM-Y） have attracted attention because of their unique properties. Nanotubes based on hybrid TMD materials have advantages in flexibility over conventional TMD nanotubes. Here we predict the wide band gap tunability of hybrid TMD double-wall nanotubes （DWNTs） from metal to semiconductor. Using density-function theory （DFT） with HSE06 hybrid functional, we find that the electronic property of X-Mo-Y DWNTs （X = O and S, inside a tube; Y = S and Se, outside a tube） depends both on electronegativity difference and diameter difference. If there is no difference in electron negativity between inner atoms （X） of outer tube and outer atoms （Y） of inner tube, the band gap of DWNTs is the same as that of the inner one. If there is a significant electronegativity difference, the electronic property of the DWNTs ranges from metallic to semiconducting, depending on the diameter differences. Our results provide alternative ways for the band gap engineering of TMD nanotubes.

Quantum nutcracker for near-room-temperature H_2 dissociation

Solid surfaces are well known to mediate the dissociation of molecules via electronic interactions (heterogeneous catalysis).In particular,H2 dissociation on metal surfaces has been widely studied for several decades because it is an important step in hydrogenation reactions.The efficiency of the process depends on both the electronic properties of the metal surface and the surface microstructures [1].Enhanced efficiency and reduced cost are usually achieved by using nanoparticles,which have increased the surface-to-volume ratio and low-coordination atoms [2].Another approach is to optimize the local electronic states of the metal surface by doping [3],alloying with other elements [4],or by taking advantage of strong interactions between metal nanoparticles and the supporting substrate [5].These methods often work together to tailor the adsorption properties on surfaces and show major efficiency enhancement.

Olefin-linked covalent organic frameworks with twisted tertiary amine knots for enhanced ultraviolet detection

Though Olefin-linked covalent organic frameworks(oCOFs)possess excellentπ-electron delocalization,the barely reversible olefin linkage brings challenges for oCOFs’synthesis and functionalization.Here,we synthesize new oCOFs with tertiary amine knots which have twisted configuration and electron-donating nature.Investigation into the structural variation and photoelectric performance shows that the twisted configuration of oCOF-TFPA could favor to the intramolecular charge transfer process and reduce the pos-sibility of aggregation-caused quenching.Photoelectrical measurements and electric band structure cal-culation both verify the superiority of this oCOFs’structure in photoelectric sensing.

Monolayer puckered pentagonal VTe_(2):An emergent two-dimensional ferromagnetic semiconductor with multiferroic coupling

Two-dimensional(2D)magnetic crystals have been extensively explored thanks to their potential applications in spintronics,valleytronics,and topological superconductivity.Here we report a novel monolayer magnet,namely puckered pentagonal VTe_(2)(PP-VTe_(2)),intriguing atomic and electronic structures of which were firmly validated from first-principles calculations.The PP-VTe_(2) exhibits strong intrinsic ferromagnetism and semiconducting property distinct from the half-metallic bulk pyrite VTe_(2)(BP-VTe_(2))phase.An unusual magnetic anisotropy with large magnetic exchange energies is found.More interestingly,the multiferroic coupling between its 2D ferroelasticity and in-plane magnetization is further identified in PP-VTe_(2),lending it unprecedented controllability with external strains and electric fields.Serving as an emergent 2D ferromagnetic semiconductor with a novel crystal structure,monolayer PP-VTe_(2) provides an ideal platform for exploring exotic crystalline and spin configurations in low-dimensional systems.

Direct evidence of two-dimensional electron gas-like band structures in hafnene

Two-dimensional(2D)honeycomb-like materials have been widely studied due to their fascinating properties.In particular,2D honeycomb-like transition metal monolayers,which are good 2D ferromagnet candidates,have attracted intense research interest.The honeycomb-like structure of hafnium,hafnene,has been successfully fabricated on the Ir(111)substrate.However,its electronic structure has not yet been directly elucidated.Here,we report the electronic structure of hafnene grown on the Ir(111)substrate using angle-resolved photoemission spectroscopy(ARPES).Our results indicate that the presence of spin-orbit coupling and Hubbard interaction suppresses the earlier predicted Dirac cones at the K points of the Brillouin zone.The observed band structure of hafnene near the Fermi level is very simple:an electron pocket centered at theΓpoint of the Brillouin zone.This electron pocket shows typical parabolic dispersion,and its estimated electron effective mass and electron density are approximately 1.8_(me)and 7×10^(14)cm^(-2),respectively.Our results demonstrate the existence of 2D electron gas in hafnene grown on the Ir(111)substrate and therefore provide key information for potential hafnene-based device applications.

Intriguing one-dimensional electronic behavior in emerging two-dimensional materials

Tomonaga-Luttinger liquid(TLL),a peculiar one-dimensional(1D)electronic behavior due to strong correlation,was first studied in 1D nanostructures and has attracted significant attention over the last several decades.With the rise of new two-dimensional(2D)quantum materials,1D nanostructures in 2D materials have provided a new platform with a well-defined configuration at the atomic scale for studying TLL electronic behavior.In this paper,we review the recent progress of TLL electronic features in emerging 2D materials embedded with various 1D nanostructures,including island edges,domain walls,and 1D moirépatterns.Specifically,novel physical phenomena,such as 1D edge states in 2D transition metal dichalcogenides(TMDs),helical TLL in 2D topological insulators(2DTI),and chiral TLL in 2D quantum Hall systems,are described and discussed at the nanoscale.We also analyze challenges and opportunities at the frontier of this research area.

Fabrication and manipulation of nanosized graphene homojunction with atomically-controlled boundaries

Controlling the atomic configurations of structural defects in graphene nanostructures is crucial for achieving desired functionalities.Here,we report the controlled fabrication of high-quality single-crystal and bicrystal graphene nanoislands(GNI)through a unique top-down etching and post-annealing procedure on a graphite surface.Low-temperature scanning tunneling microscopy(STM)combined with density functional theory calculations reveal that most of grain boundaries(GBs)formed on the bicrystal GNIs are 5-7-5-7 GBs.Two nanodomains separated by a 5-7-5-7 GB are AB stacking and twisted stacking with respect to the underlying graphite substrate and exhibit distinct electronic properties,forming a graphene homojunction.In addition,we construct homojunctions with alternative AB/twisted stacking nanodomains separated by parallel 5-7-5-7 GBs.Remarkably,the stacking orders of homojunctions are manipulated from AB/twist into twist/twist type through a STM tip.The controllable fabrication and manipulation of graphene homojunctions with 5-7-5-7 GBs and distinct stacking orders open an avenue for the construction of GBs-based devices in valleytronics and twistronics.