Lattice Parameters Research Articles

Studies of Phase Transformation Kinetics in the System of Nanocrystalline Iron/Ammonia/Hydrogen at the Temperature of 350 °C by Means of Magnetic Permeability In Situ Measurement

The kinetics of phase transformations in the nitriding process α-Fe → γ’-Fe4N → ε-Fe3-2N of the pre-reduced iron ammonia synthesis catalyst was investigated under in situ conditions (atmospheric pressure, 350 °C) by measuring changes of mass, gas phase composition, and magnetic permeability in a differential tubular reactor. The iron nanocrystallite size distribution according to their specific active surface areas was measured, and it was found that the catalyst is bimodal as the sum of two Gaussian distributions, also differing in the value of the relative magnetic permeability. Relative magnetic permeability of small α-Fe crystals in relation to large crystals is higher by 0.02. In the area of α → γ’ transformation, the magnetic permeability dependencies change, proving the existence of two mechanisms of the α-Fe structure change in the α-Fe → γ’-Fe4N transformation. In the first area, a solution of α-Fe (N) is formed with a continuous and insignificant change of the crystal lattice parameters of the iron lattice. In the second area, there is a step, oscillatory change in the parameters of the iron crystal lattice in FexN (x = 0.15, 0.20, 0.25 mol/mol). In the range of γ’-Fe4N → ε-Fe3-2N transformation, a solution is formed, with nitrogen concentration varying from 0.25–0.45 mol/mol. During the final stage of the nitriding process, at a constant value of the relative magnetic permeability, only the concentration of nitrogen in the solution εr increases. The rate of the phenomenon studied is limited by a diffusion rate through the top layer of atoms on the surface of iron nanocrystallite. The estimated value of the nitrogen diffusion coefficient varied exponentially with the degree of nitriding. In the area of the solution, the diffusion coefficient is approximately constant and amounts to 5 nm2/s. In the area of oscillatory changes, the average diffusion coefficient changes in the range of 3–11 nm2/s, and is inversely proportional to the nitrogen content degree. The advantage of the research method proposed in this paper is the possibility of simultaneously recording, under reaction conditions, changes in the values of several process parameters necessary to describe the process. The research results obtained in this way can be used to develop such fields of knowledge as heterogeneous catalysis, materials engineering, sensorics, etc.

Empirical Interatomic Potential Development and Classical Molecular Dynamics Simulation of Monolayer Group-III Monochalcogenides: Insights into Thermal Transport Properties

Abstract This research addresses the lack of comprehensive studies utilizing classical molecular dynamics simulations for monolayer group-III monochalcogenide materials. These materials, including GaS, GaSe, and InSe, have shown promise for diverse applications but lack well-defined empirical interatomic potentials in the literature. This study is concentrated on the development of empirical interatomic potential parameters for these materials using the particle swarm optimization method, filling a gap in the literature regarding classical molecular dynamics simulations. The parameters are optimized based on fundamental physical characteristics such as the lattice constants, bond lengths, phonon dispersions, and the equation of state, obtained from first-principles calculations. The developed potential parameters are then employed to predict lattice thermal conductivity through non-equilibrium classical molecular dynamics simulations, providing insights into the thermal transport properties of these materials.

Crystal structure of perfluorononanoic acid, C9HF17O2

The crystal structure of perfluorononanoic acid (PFNA) was solved via parallel tempering using synchrotron powder diffraction data obtained from the Brockhouse X-ray Diffraction and Scattering (BXDS) Wiggler Lower Energy (WLE) beamline at the Canadian Light Source. PFNA crystallizes in monoclinic space group P21/c (#14) with lattice parameters a = 26.172(1) Å, b = 5.6345(2) Å, c = 10.9501(4) Å, and β = 98.752(2)°. The crystal structure is composed of dimers, with pairs of PFNA molecules connected by hydrogen bonds via the carboxylic acid functional groups. The Rietveld-refined structure was compared to a density functional theory-optimized structure, and the root-mean-square Cartesian difference was larger than normally observed for correct powder structures. The powder data likely exhibited evidence of disorder which was not successfully modeled.

Epitaxial crystallization of polylactic acid on layered zinc phenylphosphonate: Mutual perpendicular rodlike crystals under two lattice matchings

AbstractAs a highly effective nucleating agent, layered zinc phenylphosphonate (PPZn) is incorporated into polylactic acid (PLA) to investigate the epitaxial crystallization of PLA on PPZn in this study. The corresponding lattice spacing change, crystalline morphology, and crystalline structure are emphasized to reveal the epitaxial crystallization mechanism. As a result, with the increase of PPZn content and the annealing time, the increasing lattice spacing of PPZn and the formation of mutually perpendicular rodlike crystals are observed through x‐ray diffraction (XRD) and polarized optical micrograph (POM) measurements, implying that the interlayer spacing of PPZn crystals is expanded as the PLA α‐form crystals epitaxially grow on its surface, that is, epitaxial crystallization. To be specific, “edge on” lamellae epitaxial grow on the PPZn crystals along the [010] and [100] directions under two excellent lattice matchings, which possess acceptable mismatching of 0.347% and 7.5%, respectively. With the support of the epitaxial crystallization mechanism, the occurrence of the filamentous structure observed in the fracture morphology of PLA/PPZn composites suggests strong interfacial adhesion between PLA and PPZn, which makes the impact toughness of the PLA/PPZn composites increase by 53.6% compared with pure PLA.

Effective spin models and magnetic phases of an insulating bosonic ladder with unconventional synthetic flux

Abstract We investigate the Mott insulating phases of a two-component bosonic lattice gas in the presence of gauge field. Such a system is described by a two-leg ladder model with an unconventional flux. The synthetic flux is generated by the spin-dependent tunneling and the site-dependent spin-flip. In the Mott regime, these two effects lead to Dzyaloshinskii-Moriya (DM) interaction and an external field that is rotating in the xy-plane. We obtain a very general XYZ model with the DM interaction, the spiral field, and the transverse field. Various interesting magnetic Hamiltonians can be covered by adjusting lattice parameters. The DM interaction or the spiral field can lead to spiral order when they appear alone. The interplay of DM coupling and spiral field leads to the emergence of a new multi-frequency spiral order between the paramagnetic phase and the spiral ferromagnetic phase. Ground state phases are investigated by focusing on order parameters, spin-spin correlation functions, and structure factors. Calculations are performed by using time evolution block decimation (TEBD) based on matrix product state (MPS).

Synthesis Studies of HDTDHP-μ Crystals from Arundina graminifolia Specimen for Electronic, Photonic, Optical and Electrical Use Correlated with Macro-Crystals for Sensor and Display Uses

Abstract A 7-hydroxy-2,4-dimethoxy-9,10-dihydrophenanthrene-HDTDHP macro-crystalline sample is synthesized in a time duration of 23 days with a monoclinic form of crystal with space group as P21/n and the lattice constants are slightly higher than earlier reported macro-HDTDHP. The macro ones are well-milled to get the micro ones and a scanning electron microscopy study of the HDTDHP-μ crystal was analyzed to identify the micro level average scaling in microns. The increased value of the dielectric constant at lower range of frequencies is by the effect of all kinds of polarizations; also, the dielectric loss is measured as decrease in values with the increase in frequencies at room temperature. The electronic-micro filter use is 4.0196 microns for micro influx as the proper opto-electronic, extended NLO type employability as ascertained from transmittance spectral data. The HDTDHP micro-crystalline material is mainly used in micro-photonics, in filtering as micro-influx delineation, in NLO usefulness as opto-electronic agent by the transmittance data and in frequency enhancing and projective utilization in displays. Also, display profile of (111) mode of HDTDHP by without and with recursively assigned colors for RGBR polygonal matrix by software and sensor work sensitiveness of both scaling are measured and reported.

Semiconductor-metal transition in TlPbF3 under isotropic pressure and its impact on optical, elastic and mechanical properties: A DFT computation with HSE06

Abstract This research aims to comprehensively evaluate the structure, elasticity, mechanics, anisotropy, electrical properties, and optical attributes of TlPbF3 at pressures from 0 to 60 GPa. A cubic structure of the material remains same without any phase changes, but there is a reduction in the lattice parameters. The material is determined to be mechanically secure by doing calculations on a variety of mechanical and elastic characteristics, including bulk, shear, and Young's modulus, stiff, and not particularly flexible. It also shows a significant resistance to shear force. The material's ability to withstand high pressures, its metallic bond nature, and ductility have been shown by the Kleinman's parameter, Poisson's ratio, Cauchy pressure, and Pugh ratio. Anisotropy can be confirmed by activating specific anisotropy factors. When we consider the electronic band structure, we observe a transition from a broad gap in the band (3.719 eV) comparable with a small band distance (0.65 eV), and converts to a metal (0 eV). To explore this, we have estimated the total, partial and elemental partial density of states. Additionally, we have computed the real and imaginary functions of dielectric, absorption factor, refractive index, extinction coefficient, loss function, reflectivity and real/imaginary conductivity to assess the material's applicability. As pressure is applied, the static values of ε1(⍵) and n(⍵) increase. This material is also well-suited for optoelectronic devices due to its high conductivity, reflectivity, absorption, and refractive index.

Structural characteristics of Bi2O2CO3 nanosheets synthesized by nano-pulsed discharges in water

A comprehensive analysis of Bi2O2CO3 nanosheets, which were synthesized using nanosecond-pulsed discharges in water between bismuth electrodes, was conducted in order to investigate the crystallographic features of this material. Electron diffraction, X-ray diffraction and electron energy-loss spectrometry techniques revealed the presence of a stoichiometric tetragonal Bi2O2CO3 structure, labelled BOC in this study. It crystallizes in the body-centred tetragonal Bravais lattice and belongs to the I4/mmm space group (No. 139), with the following lattice parameters: a = 3.91, c = 13.77 Å. The nanosheets adopt square shapes. This shape is dictated by the symmetry elements of its point group (4/mmm) under the prevailing local conditions. From the energetic point of view, this shape, dictated by the 4/m2/m2/m point group and therefore a pinacoid, corresponds to an absolute extremum, an indicator of the stability of these BOC nanosheets. Most nanosheets are crossed by equal-inclination fringes or bend contours. These bend contours reflect the fact that the BOC nanosheets contain crystal defects and/or are so thin that they bend elastically, leading to rotation of the lattice planes towards the diffracting Bragg position. The diffraction patterns corresponding to bend contours intersecting along the [001] zone axis have been studied in detail. Extra reflections are superimposed on the diffraction pattern of the BOC crystallographic structure. These extra reflections are essentially attributed to two phenomena: multiple diffraction and local disorder–order transformations of the BOC crystal structure, passing from a body-centred tetragonal to a primitive Bravais lattice. A mechanism related to the ledge mechanism (kinks and jogs), explaining the formation of nanosheets in a metallic matrix, has been adapted and proposed for the formation of BOC nanosheets in water. When the nanosheets are removed from the water, they become carbonated once in the air, leading to the formation of BOC that inherits the nanosheet morphology.

DFT study of the brownmillerite-type strontium-based oxygen-deficient perovskites SrTMO2.5 (TM = Mn, Fe, Co and Cu)

DFT studies are performed to investigate the crystal structure and geometry, electronic and magnetic properties of brownmillerite-type strontium-based oxygen-deficient perovskites [Formula: see text] (TM = Mn, Fe, Co and Cu) in orthorhombic phase. The comparison of the calculated lattice parameters shows consistency with the experiments, and all these perovskites are thermodynamically stable as revealed by cohesive energy. The spin-dependent calculations of the electronic band profiles demonstrate the metallic behavior of all these deficient perovskites. The increase in electrical resistivity and electronic thermal conductivities with temperature also confirms the metallic behavior of these compounds. The optimized ground state energies in different magnetic phases and post-DFT treatment confirm that [Formula: see text] and [Formula: see text] are stable in C-type AFM, [Formula: see text] is in G-type AFM and [Formula: see text] in A-type AFM phase, respectively. The high specific heat of these deficient perovskites makes them good candidates for high-temperature technology. Based on the above physical properties, it is expected that these deficient perovskites are potential candidates for spintronics and magnetic storage devices.

Anion Doping and Dual-Carbon Confinement Strategies to Synergistically Boost the Sodium Storage Performance of Cobalt-Based Sulfides.

Cobalt-based sulfides (CSs) are generally regarded as potentially valuable anode materials for sodium-ion batteries (SIBs) due to their excellent theoretical capacity and natural abundance. Nevertheless, their slow reaction kinetics and poor structural stability restrict the practical application of the materials. In this study, the dual-carbon-confined Se-CoS2@NC@C hollow nanocubes with anion doping are synthesized using ZIF-67 as the substrate by resorcin-formaldehyde (RF) encapsulation and subsequent carbonization and sulfurization/selenization. RF- and ZIF-67-derived dual-carbon skeleton hollow structures with a robust carbon skeleton and abundant internal space minimize cyclic stress, mitigate volume changes and maintain the structural integrity of the material. More importantly, Se doping increases the lattice spacing of CoS2, weakens the strength of Co-S bonds, and modulates the electronic structure around Co atoms, thereby optimizing the adsorption energy of the material. As a result, the hollow nanocubes of Se-CoS2@NC@C demonstrates excellent electrochemical performance as the anode for SIBs, delivering a high reversible capacity of 549.4 mAh g-1 at 0.5 A g-1 after 100 cycles and a superb rate performance (541.1 mAh g-1 at 0.2 A g-1, and 393.3 mAh g-1 at 5 A g-1). This study proposes a neoteric strategy for synthesizing advanced anodes for SIBs through the synergy of anion doping engineering and dual-carbon confinement strategy.

Design, Synthesis, and Characterization of Polyoxotungstate-Decorated Ionic Liquid-Based Hybrid Material, [BmIm]4[SiW12O40] toward Rapid Adsorption of Dye and Antibacterial Activities.

A multifunctional polyoxometalate-ionic liquid (POM-IL)-based hybrid material comprising silicotungstic acid, [BmIm]4[SiW12O40], has been synthesized and demonstrated its efficiency toward methylene blue removal and as an antibacterial agent. Single-crystal XRD analysis confirms that the material crystallizes in monoclinic symmetry (SG: Pn), with lattice parameters a = 13.1396(5) Å, b = 16.9655(8) Å, c = 14.3493(7) Å, and Z = 2. The structure comprises a single polyanionic [SiW12O40]4- moiety surrounded by four cationic [BmIm]+ units of two different conformations, which supported DFT and Hirshfeld surface analysis. The material shows excellent removal efficiency for methylene blue, with a maximum adsorption capacity of 92.47 mg/g and 83.05% reusability after five cycles. On the contrary, FTIR and ζ-potential analyses confirm that electrostatic interactions are the predominant factors governing the adsorption process. The material also acts as a superior antibacterial agent against the opportunistic pathogens Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli with a MIC of 500-700 μg/mL. However, a comparative assessment showed that the material was more effective against P. aeruginosa compared to the other two pathogens. PXRD analysis confirms the phase purity, and FESEM and TEM analyses exhibit block-shaped morphology with particle sizes ∼2-3 μm.

ScAlInN/GaN heterostructures grown by molecular beam epitaxy

Rare-earth (RE) elements doped III-nitride semiconductors have garnered attention for their potential in advanced high-frequency and high-power electronic applications. We report on the molecular beam epitaxy of quaternary alloy ScAlInN, which is an encouraging strategy to improve the heterointerface quality when grown at relatively low temperatures. Monocrystalline wurtzite phase and uniform domain structures are achieved in ScAlInN/GaN heterostructures, featuring atomically sharp interface. ScAlInN (the Sc content in the ScAlN fraction is 14%) films with lower In contents (less than 6%) are nearly lattice matched to GaN, exhibiting negligible in-plane strain, which are excellent barrier layer candidates for GaN high electron mobility transistors (HEMTs). Using a 15-nm-thick Sc0.13Al0.83In0.04N as a barrier layer in GaN HEMT, a two-dimensional electron gas density of 4.00 × 1013 cm−2 and a Hall mobility of 928 cm2/V s, with a corresponding sheet resistance of 169 Ω/□, have been achieved. This work underscores the potential of alloy engineering to adjust lattice parameters, bandgap, polarization, interfaces, and strain in emerging RE-III-nitrides, paving the way for their use in next-generation optoelectronic, electronic, acoustic, and ferroelectric applications.

Lattice expansion in ruthenium nanozymes improves catalytic activity and electro-responsiveness for boosting cancer therapy

Nanozymes have been attracting widespread interest for the past decade, especially in the field of cancer therapy, due to their intrinsic catalytic activities, strong stability, and ease of synthesis. However, enhancing their catalytic activity in the tumor microenvironment (TME) remains a major challenge. Herein, we manipulate catalytic activities of Ru nanozymes via modulating lattice spacing in Ru nanocrystals supported on nitrogen-doped carbon support, to achieve improvement in multiple enzyme-like activities that can form cascade catalytic reactions to boost cancer cell killing. In addition, the lattice expansion in Ru nanocrystals improve the responsiveness of the nanozymes to self-powered electric field, achieving maximized cancer therapeutic outcome. Under the electrical stimulation provided by a human self-propelled triboelectric device, the Ru-based nanozyme (Ru1000) with a lattice expansion of 5.99% realizes optimal catalytic performance and cancer therapeutic outcome of breast cancer in female tumor-bearing mice. Through theoretical calculations, we uncover that the lattice expansion and electrical stimulation promote the catalytic reaction, simultaneously, by reducing the electron density and shifting the d-band center of Ru active sites. This work provides opportunities for improving the development of nanozymes.

Heterogeneous nucleation of calcium sulfate whisker in polyamide 6 and its efficient reinforcement on tribology performance

AbstractFor traditional materials, a polymer composite with high performance and large‐scale production is still the goal pursued by researchers. In our work, polyamide 6/calcium sulfate whiskers (PA6/SCW) composites were fabricated via melt‐compouding method. The calcium sulfate whisker based on gypsum mineral was used as reinforcement. After grafting silane coupling agent on the whisker surface, the whiskers showed a significant reinforcing effect in polyamide. The mechanics and tribology performance of the samples had been significantly inhanced. Based on the nucleation mechanism of lattice matching, calcium sulfate whiskers have obvious heterogeneous nucleation effect in PA6 matrix, while the crystallization period was slightly prolonged. This was caused by the network structure formed by the whiskers in the matrix, which impeded the free movement of polymer chain segments. In combination with the orientation degree of the molecular chains measured by the interdigital electrode, the reinforcing effect of the oriented PA6 specimens was derived from the orientation arrangement of the whiskers and the efficient load transfer.Highlights Mechanical and tribological properties of composite were significantly improved. The composite could achieved large‐scale production due to simple preparation. The whiskers had obvious heterogeneous nucleation effect in matrix. The reinforcing effect was derived from efficient load transfer from whiskers.

Chemochromism and Tunable Acoustic Phonons in Intercalated MoO3: Ag-, Bi-, In-, Mo-, Os-, Pd-, Pt-, Rh-, Ru-, Sb-, and W-MoO3.

Intercalation of several elements (Ag, Bi, In, Mo, Os, Pd, Pt, Rh, Ru, Sb, and W) is used to chemically alter a wide range of properties of two-dimensional layered α-MoO3. Intercalation modifies acoustic phonons and elastic constants, as measured with Brillouin scattering. Intercalation alters electronic bandgaps, color, structure, Raman shifts, and electron binding energies. Optical chemochromism is demonstrated with intercalants changing the color of MoO3 from transparent to brilliant blue (In, Mo, Os, and Ru) and orange (Ag). Correlations are investigated among material properties. There is evidence that in-plane longitudinal stiffness c11 correlates with changes in the bandgap, while various Raman modes appear to be connected to a variety of properties, including shear modulus c55, Mo binding energies, lattice constants, and the preferred crystal structure of the intercalant. The results indicate a surprising degree of complexity, suggesting competition among multiple distinct mechanisms and interactions involving specific intercalant species.

Annealing Behavior of a Mg-Y-Zn-Al Alloy Processed by Rapidly Solidified Ribbon Consolidation

Mg-Y-Zn-Al alloys processed by the rapidly solidified ribbon consolidation (RSRC) technique are candidate materials for structural applications due to their improved mechanical performance. Their outstanding mechanical strength is attributed to solute-enriched stacking faults (SESFs), which can form cluster-arranged layers (CALs) and cluster-arranged nanoplates (CANaPs) or complete the long-period stacking ordered (LPSO) phase. The thermal stability of these solute arrangements strongly influences mechanical performance at elevated temperatures. In this study, an RSRC-processed Mg—0.9%, Zn—2.05%, Y—0.15% Al (at%) alloy was heated at a rate of 0.666 K/s up to 833 K, a temperature very close to melting point. During annealing, in situ X-ray diffraction (XRD) measurements were performed using synchrotron radiation in order to monitor changes in the structure. These in situ XRD experiments were completed with ex situ electron microscopy investigations before and after annealing. At 753 K and above, the ratio of the matrix lattice constants, c/a, decreased considerably, which was restored during cooling. This decrease in c/a could be attributed to partial melting in the volumes with high solute contents, causing a change in the chemical composition of the remaining solid material. In addition, the XRD intensity of the secondary phase increased at the beginning of cooling and then remained unchanged, which was attributed to a long-range ordering of the solute-enriched phase. Both the matrix grains and the solute-enriched particles were coarsened during the heat treatment, as revealed by electron microscopy.

Mn-deficient ZnMn2O4/Zn0.5Mn0.5Fe2O4 cathode for enhancing structural reversibility and stability of zinc-ion batteries

Aqueous zinc-ion batteries have surfaced as a viable energy storage technology due to their safety, eco-friendliness, and cost-effectiveness. Binary zinc manganite oxide (ZnMn2O4 or ZMO) stands out as the potential cathode material owing to its considerable theoretical capacity and high operating voltage. However, high electrostatic repulsion of Zn2+ ions within ZMO leads to sluggish diffusion and poor reversibility of Zn2+ ions insertion/extraction that can reduce charge storage and overall cycling performance. This study addresses this challenge by introducing FeCl3 during the synthesis to form ZMO/Zn0.5Mn0.5Fe2O4 (ZMFO) cathode material. This cathode features Mn-deficient structures, which can reduce the electrostatic repulsion via low Mn occupancies and lattice parameters enlargement, thus facilitating Zn2+ ions diffusion. Ex-situ X-ray diffraction analyses further show that the cathode is able to maintain good structural reversibility during the charge-discharge cycles. Additionally, the ZMO/ZMFO cathode exhibits smaller particle sizes than pristine ZMO, providing a wider surface area. The presence of ZMFO with a large unit cell volume can also enhance Zn storage capacity and accelerate Zn2+ ions kinetics. Highlighting those advantages, aqueous zinc-ion batteries with ZMO/ZMFO cathode show a capacity of ~230 mAh g−1 at 0.05 A g−1 and retain 99 % of its initial capacity at 0.2 A g−1 after 200 cycles of charge-discharge.

Design and investigation of electrostatic doped heterostructure vertical Si(1-x)Gex/Si nanotube TFET

Researchers are inclining toward heterostructures suitable lattice matching, in Tunnel FETs to eliminate the difficulties of decreased On-Current, subthreshold swings, and ambipolar behavior. Nowadays, Electrostatic doping (ED) is a scrutinized substitute device for creating areas with a high electron or hole density to the conventional doped devices. This manuscript proposes an Electrostatic Doped Heterostructure Vertical Si(1-x)Gex/Si Nanotube Tunnel Field Effect with performance scanned by analyzing the different device parameters, considering the energy band diagram, concentrations of electrons, holes, potential, and electric field. In comparison to the Nanowire TFETs, the area, and rate of tunneling of the proposed device stand superior with a better ION/IOFF ratio of 1.56∗1013 and a lower OFF-current of about ∼10−18A/μm. The device exhibits a Drain current (IDS) of 2.39∗105A/μm. The architecture of the suggested device possessing Si(1-x)Gex/Si structure exhibits enhanced characteristics like improved steepness of the sub-threshold slope, ION/IOFF ratio, drain current, and lowered OFF-current.

Insights into effects of Fe doping on phase stability, martensitic transformation, and magnetic properties in Ni-Mn-Ti-Fe all-d-metal Heusler alloys

In this work, the effects of Fe doping on phase stability, martensitic transformation, and magnetic properties of Ni50Mn37.5-xTi12.5Fex (x = 3.125, 6.25, 9.375) all-d-metal Heusler alloys were systematically investigated by first-principles calculations. The results indicate a tendency for doped Fe atoms to aggregate within the Ni50Mn37.5-xTi12.5Fex alloys. As Fe concentration increases, a gradual reduction in both lattice constants and phase stability of austenite and martensite is observed. In the absence or presence of minimal Fe doping, both austenite and martensite exhibit antiferromagnetic behavior. However, at x = 9.375, a transition to a ferromagnetic state is observed in the austenite phase. This transition is attributed to the activation of the ferromagnetic coupling effect in the austenite phase induced by Fe doping in the Ni-Mn-Ti alloy. In contrast, the martensite phase maintains its antiferromagnetic characteristics throughout the doping range. A comprehensive analysis of the electronic structure elucidates the underlying physical mechanisms responsible for the martensitic transformation and magnetic property changes.

Epitaxial Growth of Monolayer WS2 Single Crystals on Au(111) Toward Direct Surface-Enhanced Raman Spectroscopy Detection.

The epitaxial growth of wafer-scale two-dimensional (2D) semiconducting transition metal dichalcogenides (STMDCs) single crystals is the key premise for their applications in next-generation electronics. Despite significant advancements, some fundamental factors affecting the epitaxy growth have not been fully uncovered, e.g., interface coupling strength, adlayer-substrate lattice matching, substrate step-edge-guiding effects, etc. Herein, we develop a model system to tackle these issues concurrently, and realize the epitaxial growth of wafer-scale monolayer tungsten disulfide (WS2) single crystals on the Au(111) substrate. This epitaxial system is featured with good adlayer-substrate lattice matching, obvious step-edge-guiding effect for the unidirectionally aligned nucleation/growth, and relatively weaker interfacial interaction than that of monolayer MoS2/Au(111), as evidenced by the evolution of a uniform Moiré pattern and an intrinsic band gap, according to on-site scanning tunneling microscopy/spectroscopy (STM/STS) characterizations and density functional theory calculations. Intriguingly, the unidirectionally aligned monolayer WS2 domains along the Au(111) steps can behave as ultrasensitive templates for surface-enhanced Raman scattering detection of organic molecules, due to the obvious charge transfer occurred at substrate step edges. This work should hereby deepen our understanding of the epitaxy mechanism of 2D STMDCs on single-crystal substrates, and propel their wafer-scale production and applications in various cutting-edge fields.