Classical computation of electronic properties in large-scale materials remains challenging.Quantum computation has the potential to offer advantages in memory footprint and computational scaling.However,general and v...Classical computation of electronic properties in large-scale materials remains challenging.Quantum computation has the potential to offer advantages in memory footprint and computational scaling.However,general and viable quantum algorithms for simulating large-scale materials are still limited.We propose and implement random-state quantum algorithms to calculate electronic-structure properties of real materials.Using a random state circuit on a small number of qubits,we employ real-time evolution with first-order Trotter decomposition and Hadamard test to obtain electronic density of states,and we develop a modified quantum phase estimation algorithm to calculate real-space local density of states via direct quantum measurements.Furthermore,we validate these algorithms by numerically computing the density of states and spatial distributions of electronic states in graphene,twisted bilayer graphene quasicrystals,and fractal lattices,covering system sizes from hundreds to thousands of atoms.Our results manifest that the random-state quantum algorithms provide a general and qubit-efficient route to scalable simulations of electronic properties in large-scale periodic and aperiodic materials.展开更多
High-pressure electrides,characterized by the presence of interstitial quasi-atoms(ISQs),possess unique electronic structures and physical properties,such as diverse dimensions of electride states exhibiting different...High-pressure electrides,characterized by the presence of interstitial quasi-atoms(ISQs),possess unique electronic structures and physical properties,such as diverse dimensions of electride states exhibiting different superconductivity,which has attracted significant attention.Here,we report a new electron-deficient type of electride Li_(4)Al and identify its phase transition progress with pressurization,where the internal driving force behind phase transitions,bonding characteristics,and superconducting behaviors have been revealed based on first-principles density functional theory.Through analysis of the bonding properties of electride Li_(4)Al,we demonstrate that the ISQs exhibiting increasingly covalent characteristics between Al ions play a critical role in driving the phase transition.Our electron–phonon coupling calculations indicate that all phases exhibit superconducting behaviors.Importantly,we prove that the ISQs behave as free electrons and demonstrate that the factor governing T_(c) is primarily derived from Li-p-hybridized electronic states with ISQ compositions.These electronic states are scattered by low-frequency phonons arising from mixed vibrations of Li and Al affected by ISQs to enhance electron–phonon coupling.Our study largely expands the research scope of electrides,provides new insight for understanding phase transitions,and elucidates the effects of ISQs on superconducting behavior.展开更多
Vacancy defects,as fundamental disruptions in metallic lattices,play an important role in shaping the mechanical and electronic properties of aluminum crystals.However,the influence of vacancy position under coupled t...Vacancy defects,as fundamental disruptions in metallic lattices,play an important role in shaping the mechanical and electronic properties of aluminum crystals.However,the influence of vacancy position under coupled thermomechanical fields remains insufficiently understood.In this study,transmission and scanning electron microscopy were employed to observe dislocation structures and grain boundary heterogeneities in processed aluminum alloys,suggesting stress concentrations and microstructural inhomogeneities associated with vacancy accumulation.To complement these observations,first-principles calculations and molecular dynamics simulations were conducted for seven single-vacancy configurations in face-centered cubic aluminum.The stress response,total energy,density of states(DOS),and differential charge density were examined under varying compressive strain(ε=0–0.1)and temperature(0–600 K).The results indicate that face-centered vacancies tend to reduce mechanical strength and perturb electronic states near the Fermi level,whereas corner and edge vacancies appear to have weaker effects.Elevated temperatures may partially restore electronic uniformity through thermal excitation.Overall,these findings suggest that vacancy position exerts a critical but position-dependent influence on coupled structure-property relationships,offering theoretical insights and preliminary experimental support for defect-engineered aluminum alloy design.展开更多
Self-trapping excitons(STEs) emission in metal halides has been a matter of interest, correlating with the strength of electron-phonon coupling in the lattice, which are usually caused by ions with ns~2 electronic str...Self-trapping excitons(STEs) emission in metal halides has been a matter of interest, correlating with the strength of electron-phonon coupling in the lattice, which are usually caused by ions with ns~2 electronic structure. In this work, Sb^(3+)/Te^(4+)ions doped Zn-based halide single crystals(SCs) with two STEs emissions have been synthesized and the possibility of its anti-counterfeiting application was explored.Further, the relationship between the strength of electron-phonon coupling and photoluminescence quantum yields(PLQYs) for STEs in a series of metal halides has been studied. And the semi-empirical range of the Huang-Rhys factors(S) for metal halides with excellent photoluminescence(PL) property has been summarized. This work provides ideas for further research into the relationship between luminescence performance and electron-phonon coupling of metal halides, and also provides a reference for designing the metal halides with high PLQYs.展开更多
Metal vanadates garner significant interest because of their exceptional potential for use in diverse practical applications,which stems from their unique framework structures,bond strength heterogeneities,and strong ...Metal vanadates garner significant interest because of their exceptional potential for use in diverse practical applications,which stems from their unique framework structures,bond strength heterogeneities,and strong O^(2-)-V^(5+)charge-transfer bands.However,their optoelectronic properties have not yet been sufficiently explored.In this study,we synthesized three high-purity calcium vanadate compounds(Ca V_(2)O_(6),Ca_(2)V_(2)O_(7),and Ca_(3)V_(2)O_(8))and comprehensively investigated their optoelectronic properties via first-principles calculations and experimental characterizations.Ca V_(2)O_(6),Ca_(2)V_(2)O_(7),and Ca_(3)V_(2)O_(8) are indirect band gap semiconductors with band gaps of 2.5-3.4 e V.A comparative analysis between density functional theory(DFT)and DFT+U(local Coulomb interaction,U)calculations revealed that standard DFT was sufficient to accurately describe the lattice parameters and band gaps of these vanadates.Further luminescence studies revealed significant photo-and electro-luminescence properties within the visible light spectrum.Notably,the luminescence intensity of CaV_(2)O_(6) exhibited a remarkable 10-fold enhancement under a modest pressure of only 0.88 GPa,underscoring its exceptional potential for use in pressure-tunable optical applications.These findings provide deeper insight into the electronic structures and optical behaviors of vanadates and highlight their potential as strong candidates for application in phosphor materials and optoelectronic devices.展开更多
This study investigates the structural,electronic,vibrational,and mechanical properties of cubic InTe using density functional theory and density functional perturbation theory.The results reveal the metallic characte...This study investigates the structural,electronic,vibrational,and mechanical properties of cubic InTe using density functional theory and density functional perturbation theory.The results reveal the metallic character of cubic InTe,as indicated by its electronic structure and density of states.The dynamic stability of the material is confirmed by phonon dispersion analysis,with no imaginary frequencies observed.The Debye temperature(172.276 K)and melting temperature(1092.832 K)suggest excellent thermal resistance.A shear modulus of 18.20 GPa,Poisson’s ratio of 0.343,and Pugh’s ratio([Math Processing Error])of 2.87 support mechanical stability and indicate ductility.Isotropic dielectric properties,with Born effective charges of−3.768 for both In and Te atoms,highlight potential ferroelectric applications.These findings emphasize InTe’s suitability for electronic and construction applications.展开更多
Electron beam powder bed fusion(EB-PBF)offers a promising route for producing Ti_(6)Al_(4)V alloys with tailored microstructures and superior mechanical properties.Herein,EB-PBF produced nearly fully dense Ti 6Al 4V a...Electron beam powder bed fusion(EB-PBF)offers a promising route for producing Ti_(6)Al_(4)V alloys with tailored microstructures and superior mechanical properties.Herein,EB-PBF produced nearly fully dense Ti 6Al 4V alloys(≥98.5%)with basketweave microstructures containing fine equilibriumαlamellae,different from typicalα′acicular observed in materials produced via laser-PBF.The as-printed horizontal material has a yield strength(YS)of 992 MPa,an ultimate tensile strength(UTS)of 1053 MPa,and a fracture strain(ε)of 10.9%.Meanwhile,the as-printed longitudinal material shows inferior mechanical properties(YS of 934 MPa,UTS of 979 MPa,andεof 2.4%).The horizontal and longitudinal samples show notable hysteresis loops in the loading unloading reloading curves,indicating substantial heterogeneous-induced strengthening.Flow stress,back stress,and effective stress increase with increasing strain,where back stress is comparable to effective stress during the overall deformation.Furthermore,a monotonically decreased strain hardening rate with increasing strain can be attributed to dislocation activities,whose failure is related to the strain localization at theαlamellae boundary.展开更多
This study analyzed through-thickness distribution of residual stress in a 106 mm ultra-thick TC4 titanium alloy electron beam welded(EBW)joint after post weld heat treatment(PWHT)using X-ray diffraction(XRD)and deep-...This study analyzed through-thickness distribution of residual stress in a 106 mm ultra-thick TC4 titanium alloy electron beam welded(EBW)joint after post weld heat treatment(PWHT)using X-ray diffraction(XRD)and deep-hole drilling(DHD)methods,and investigated the microstructure and mechanical properties.During the PWHT at 600℃,a phase transformation(β→α)occurred in the EBW joint and affected the residual stress distribution and mechanical properties.The surface residual stress was mainly compressive stress,while the internal residual stress was mainly tensile stress in the welded joint.For the as-welded joint,the absolute value of surface residual stress was higher than the absolute value of internal residual stress.After PWHT,the residual stress in the treated joint was substantially reduced compared to the as-welded joint,particularly the surface stress,which relieved from−425 to−90 MPa.However,the residual stress relief effect had minimal positive impact on the internal region at 600℃.PWHT resulted in a shift of the joint fracture location from the fusion zone(FZ)to the base metal(BM),and therefore exerted no noticeable effect on the joint strength,but increased the joint elongation significantly.This study provides valuable insights into the regulation of residual stress distribution of ultra-thick titanium alloy plates.展开更多
Liquid-liquid phase separation(LLPS)of proteins and nucleic acids is a common phenomenon in cells that underlies the formation of membraneless organelles.Although the macroscopic behavior of biomolecular coacervates h...Liquid-liquid phase separation(LLPS)of proteins and nucleic acids is a common phenomenon in cells that underlies the formation of membraneless organelles.Although the macroscopic behavior of biomolecular coacervates has been elucidated by microscopy,the detailed dynamic properties of proteins/peptides during the LLPS process remain poorly characterized.Here,site-directed spin labeling-electron paramagnetic resonance(SDSL-EPR)spectroscopy was employed to characterize the dynamic properties of a minimal model LLPS system consisting of positively charged peptides and RNA.The degree of phase separation,indicated by broadening of the EPR spectrum of the spin-labeled peptide due to slow molecular tumbling,was monitored by EPR.In addition,three distinct populations with varying molecular motion during LLPS,featuring different spectral lineshapes,were identified.These populations included a fast motion component(Ⅰ),a slower motion component(Ⅱ)associated with peptides in the dispersed phase and an immobile component(Ⅲ)observed in the dense phase.With gradual titration of the peptides to RNA,the EPR spectrum gradually shifted,refiecting changes in the populations of the components.Together,SDSL-EPR method not only provides new insights into the dynamic behavior of biomolecules during LLPS,but also offers a sensitive method for biomolecular phase separation processes at the molecular level.展开更多
(NbZrHfTi)C high-entropy ceramics,as an emerging class of ultra-high-temperature materials,have garnered significant interest due to their unique multi-principal-element crystal structure and exceptional hightemperatu...(NbZrHfTi)C high-entropy ceramics,as an emerging class of ultra-high-temperature materials,have garnered significant interest due to their unique multi-principal-element crystal structure and exceptional hightemperature properties.This study systematically investigates the mechanical properties of(NbZrHfTi)C high-entropy ceramics by employing first-principles density functional theory,combined with the Debye-Grüneisen model,to explore the variations in their thermophysical properties with temperature(0–2000 K)and pressure(0–30 GPa).Thermodynamically,the calculated mixing enthalpy and Gibbs free energy confirm the feasibility of forming a stable single-phase solid solution in(NbZrHfTi)C.The calculated results of the elastic stiffness constant indicate that the material meets the mechanical stability criteria of the cubic crystal system,further confirming the structural stability.Through evaluation of key mechanical parameters—bulk modulus,shear modulus,Young’s modulus,and Poisson’s ratio—we provide comprehensive insight into the macro-mechanical behaviour of the material and its correlation with the underlying microstructure.Notably,compared to traditional binary carbides and their average properties,(NbZrHfTi)C exhibits higher Vickers hardness(Approximately 28.5 GPa)and fracture toughness(Approximately 3.4 MPa⋅m^(1/2)),which can be primarily attributed to the lattice distortion and solid-solution strengthening mechanism.The study also utilizes the quasi-harmonic approximation method to predict the material’s thermophysical properties,including Debye temperature(initial value around 563 K),thermal expansion coefficient(approximately 8.9×10^(−6) K−1 at 2000 K),and other key parameters such as heat capacity at constant volume.The results show that within the studied pressure and temperature ranges,(NbZrHfTi)C consistently maintains a stable phase structure and good thermomechanical properties.The thermal expansion coefficient increasing with temperature,while heat capacity approaches the Dulong-Petit limit at elevated temperatures.These findings underscore the potential of(NbZrHfTi)C applications in ultra-high temperature thermal protection systems,cutting tool coatings,and nuclear structural materials.展开更多
Fe-Mo functionally graded materials(FGMs)with different composition-change rates from 100%304 stainless steel to 100%Mo along the composition gradient direction were prepared by electron beam-directed energy depositio...Fe-Mo functionally graded materials(FGMs)with different composition-change rates from 100%304 stainless steel to 100%Mo along the composition gradient direction were prepared by electron beam-directed energy deposition(EB-DED)technique,including three samples with composition mutation of 100%,composition change rate of 10%and 30%.Results show that the composition-change rate significantly affects the microstructure and mechanical properties of the samples.In the sample with abrupt change of composition,the sharp shift in composition between 304 stainless steel and Mo leads to a great difference in the microstructure and hardness near the interface between the two materials.With the increase in the number of gradient layers,the composition changes continuously along the direction of deposition height,and the microstructure morphology shows a smooth transition from 304 stainless steel to Mo,which is gradually transformed from columnar crystal to dendritic crystal.Elements Fe,Mo,and other major elements transform linearly along the gradient direction,with sufficient interlayer diffusion between the deposited layers,leading to good metallurgical bonding.The smaller the change in composition gradient,the greater the microhardness value along the deposition direction.When the composition gradient is 10%,the gradient layer exhibits higher hardness(940 HV)and excellent resistance to surface abrasion,and the overall compressive properties of the samples are better,with the compressive fracture stress in the top region reaching 750.05±14 MPa.展开更多
Titanium aluminide(TiAl)alloys,known for their light weight and high specific strength,hold promising potential for aerospace applications.Recent studies have focused on improving their properties through composite st...Titanium aluminide(TiAl)alloys,known for their light weight and high specific strength,hold promising potential for aerospace applications.Recent studies have focused on improving their properties through composite strengthening.An in situ synthesized Ti_(5)Si_(3)-reinforced TiAl composite with excellent performance was successfully fabricated via a dual-wire electron beam-directed energy deposition(EB-DED)process.The microstructure of the as-deposited Ti_(5)Si_(3)/TiAl composite consisted of primary Ti_(5)Si_(3)rods,eutectic Ti_(5)Si_(3)needles,and lamellar TiAl+Ti_(3)Al structures.The phase transformation during the EB-DED process was L→Ti_(5)Si_(3)+L→Ti_(5)Si_(3)+(α+Ti_(5)Si_(3))Eutectic→Ti_(5)Si_(3)+(Ti3Al+TiAl)Eutectoid.The expanded Blackburn orientation relationships among the ternary phases emerged from the eutectic reaction of L→α+Ti_(5)Si_(3)with an undercooling exceeding 136°C and the subsequent eutectoid reaction with ordering transformation and were expressed as<1120>TisAl//<10I0>Ti_(5)Si_(3)//<110]Ti_(3)Al and{0001}TiзA//{0001}Ti_(5)Si_(3)//{111}TiAl.The Ti_(5)Si_(3)phase had a greater hardness than did the lamellar structures and enhanced the mechanical properties of the matrix.The compressive yield strengths at room temperature and 750°C were 1221±51 and 1034±34 MPa,respectively,whereas the tensile yield strength was 347.4±12.7 MPa at 950°C,surpassing those of other TiAl alloys.The calculated strength with different strengthening mechanisms was 1056.4 MPa,and the greatest improvement in strength was attributed to the decreased interlamellar spacing.This work provides critical insight into the design of TiAl composites with superior mechanical properties and aids in understanding the microstructural evolution of as-deposited Ti_(5)Si_(3)/TiAl composites.展开更多
Nitrogen doping in chemical vapor deposition-derived ultrananocrystalline diamond(UNCD)films in-creases the electronic conductivity,yet its microstructural effects on electron transport are insufficiently understood.W...Nitrogen doping in chemical vapor deposition-derived ultrananocrystalline diamond(UNCD)films in-creases the electronic conductivity,yet its microstructural effects on electron transport are insufficiently understood.We investigated the formation of nitrogen-induced diaph-ite structures(hybrid diamond-graphite phases)and their role in changing the conductivity.Nitrogen doping in a hy-drogen-rich plasma environment promotes the emergence of unique sp^(3)-sp^(2)bonding interfaces,where diamond grains are covalently integrated with graphitic domains,facilitating a structure-driven electronic transition.High-resolution transmis-sion electron microscopy and selected area electron diffraction reveal five-fold,six-fold and twelve-fold symmetries,along with an atypical{200}crystallographic reflection,confirming diaphite formation in 5%and 10%N-doped UNCD films,while high-er doping levels(15%and 20%)result in extensive graphitization.Raman spectroscopy tracks the evolution of sp^(2)bonding with increasing nitrogen content,while atomic force microscopy and X-ray diffraction indicate a consistent diamond grain size of~8 nm.Cryogenic electronic transport measurements reveal a conductivity increase from 8.72 to 708 S/cm as the nitrogen dop-ing level increases from 5%to 20%,which is attributed to defect-mediated carrier transport and 3D weak localization.The res-ulting conductivity is three orders of magnitude higher than previously reported.These findings establish a direct correlation between diaphite structural polymorphism and tunable electronic properties in nitrogen-doped UNCD films,offering new ways for defect-engineering diamond-based electronic materials.展开更多
Only a few studies have reported the efects of electrochemical hydrogenation on the tensile mechanical properties of additively manufactured Ti–6Al–4V alloy,in all of them the alloy was processed by laser powder-bed...Only a few studies have reported the efects of electrochemical hydrogenation on the tensile mechanical properties of additively manufactured Ti–6Al–4V alloy,in all of them the alloy was processed by laser powder-bed fusion.Furthermore,the efects of either hot isostatic pressing(HIP)or heat treatment(HT)post-treatments on the mechanical properties were not reported.Here,the Young’s modulus,ultimate tensile stress,and uniform(homogeneous)strain of as-built electron beam melted(EBM)Ti–6Al–4V alloys were studied using small tensile specimens before and after electrochemical hydrogenation,as well as before and after secondary processes of HIP at 920℃ and HT at 1000℃.The tensile properties of all hydrogenated alloys were signifcantly degraded compared to their non-hydrogenated counterparts.The yield stress could not be determined for all hydrogenated alloys,as failure occurred at a strain below 0.2%ofset.The uniform strain of the hydrogenated alloys was less than 1%,compared to 1%–5%for the non-hydrogenated alloys.The fracture mode of the hydrogenated alloys after HIP and HT revealed cleavage fracture,indicating increased brittleness.In the as-built hydrogenated alloy,the fracture mode varied with location:brittle fracture occurred near the surface due to the formation of a hydride layer,while a more ductile fracture with dimples was observed below this layer.展开更多
The structural,relative stability,and electronic properties of two-dimensional AsP_(2)X_(6)(X=S,Se)were predicted and studied using the particle-swarm optimization method and first principles calculations.We proposed ...The structural,relative stability,and electronic properties of two-dimensional AsP_(2)X_(6)(X=S,Se)were predicted and studied using the particle-swarm optimization method and first principles calculations.We proposed two low energy structures with P312 and P-31m phases,both of which the structures are hexagonal in shape and show non-centrosymmetry for the P312 phase and centrosymmetry for the P-31m phase.According to our results,two structural phases are found to be stable thermally and dynamically.The P312 phase of AsP_(2)X_(6)(X=S,Se)are indirect semiconductors with band gaps of 2.44 eV(AsP2S6)and 2.18 eV(AsP2Se6)at the HSE06 level,and their absorption coefficients are predicted to reach the order of 10^(5)cm^(-1)from visible light to ultraviolet region,but the main absorption is manly in the ultraviolet region.The P-31m phase of AsP_(2)X_(6)(X=S,Se)exhibits metal character with the Fermi surface mainly occupied by the p orbital of S/Se.Remarkably,estimated by first principles calculations,the P-31m AsP2S6 is found to be an intrinsic phonon-mediated superconductor with a relatively high critical superconducting temperature of about 13.4 K,and the P-31m AsP2Se6 only has a superconducting temperature of 1.4 K,which suggest that the P-31m AsP2S6 may be a good candidate for a nanoscale superconductor.展开更多
The effects of pressure on the structural stability,elasticity,electronic properties,and thermodynamic properties of Al,Al_(3)Cu,Al_(2)Cu,Al_(4)Cu_(9),AlCu_(3),and Cu were investigated using first-principles calculati...The effects of pressure on the structural stability,elasticity,electronic properties,and thermodynamic properties of Al,Al_(3)Cu,Al_(2)Cu,Al_(4)Cu_(9),AlCu_(3),and Cu were investigated using first-principles calculations.The experimental results indicate that the calculated equilibrium lattice constant,elastic constant,and elastic modulus agree with both theoretical and experimental data at 0 GPa.The Young's modulus,bulk modulus,and shear modulus increase with increasing pressure.The influence of pressure on mechanical properties is explained from a chemical bond perspective.By employing the quasi-harmonic approximation model of phonon calculation,the temperature and pressure dependence of thermodynamic parameters in the range of 0 to 800 K and 0 to 100 GPa are determined.The findings demonstrate that the thermal capacity and coefficient of thermal expansion increase with increasing temperature and decrease with increasing pressure.This study provides fundamental data and support for experimental investigations and further theoretical research on the properties of aluminum-copper intermetallic compounds.展开更多
Density functional theory(DFT)studies were performed on the lattice parameters,electronic band structure,and optical constants under pressure up to 20 GPa in order to obtain insight into the electronic and optical pro...Density functional theory(DFT)studies were performed on the lattice parameters,electronic band structure,and optical constants under pressure up to 20 GPa in order to obtain insight into the electronic and optical properties of LiZnAs.The calculated results show LiZnAs is a semiconductor with a direct gap of 0.86 eV,which is smaller than the experimental value 1.1 eV.It also indicates that the structural parameters such as lattice parameters and cell volume show inverse relation to the pressure and shows smooth decreasing behavior from 0 to 20 GPa.Meanwhile,the pressure dependence of the electronic band structure,density of states and partial density of states of LiZnAs up to 20 GPa were presented.And we found that the band gap increased with the pressure.Moreover,the evolution of the dielectric function,absorption coefficient a(w),reflectivity R(w),the refractive index n(w),and the extinction coefficient k(w)of LiZnAs under pressure were presented.According to our work,we found that the optical properties of LiZnAs undergo a blue shift with increasing pressure.These results suggest technological applications of such materials in extreme environments.展开更多
基金supported by the Major Project for the Integration of ScienceEducation and Industry (Grant No.2025ZDZX02)。
文摘Classical computation of electronic properties in large-scale materials remains challenging.Quantum computation has the potential to offer advantages in memory footprint and computational scaling.However,general and viable quantum algorithms for simulating large-scale materials are still limited.We propose and implement random-state quantum algorithms to calculate electronic-structure properties of real materials.Using a random state circuit on a small number of qubits,we employ real-time evolution with first-order Trotter decomposition and Hadamard test to obtain electronic density of states,and we develop a modified quantum phase estimation algorithm to calculate real-space local density of states via direct quantum measurements.Furthermore,we validate these algorithms by numerically computing the density of states and spatial distributions of electronic states in graphene,twisted bilayer graphene quasicrystals,and fractal lattices,covering system sizes from hundreds to thousands of atoms.Our results manifest that the random-state quantum algorithms provide a general and qubit-efficient route to scalable simulations of electronic properties in large-scale periodic and aperiodic materials.
基金supported by the National Key Research and Development Program of China (Grant Nos.2023YFA1406200 and 2022YFA-1405500)the National Natural Science Foundation of China (Grant Nos.12304021 and 52072188)+3 种基金Zhejiang Provincial Natural Science Foundation of China (Grant Nos.LQ23A040004 and MS26A040028)Natural Science Foundation of Ningbo (Grant Nos.2022J091 and ZX2025001430)the Program for Science and Technology Innovation Team in Zhejiang (Grant No.2021R01004)the Program for Changjiang Scholars and Innovative Research Team in University (Grant No.IRT_15R23)。
文摘High-pressure electrides,characterized by the presence of interstitial quasi-atoms(ISQs),possess unique electronic structures and physical properties,such as diverse dimensions of electride states exhibiting different superconductivity,which has attracted significant attention.Here,we report a new electron-deficient type of electride Li_(4)Al and identify its phase transition progress with pressurization,where the internal driving force behind phase transitions,bonding characteristics,and superconducting behaviors have been revealed based on first-principles density functional theory.Through analysis of the bonding properties of electride Li_(4)Al,we demonstrate that the ISQs exhibiting increasingly covalent characteristics between Al ions play a critical role in driving the phase transition.Our electron–phonon coupling calculations indicate that all phases exhibit superconducting behaviors.Importantly,we prove that the ISQs behave as free electrons and demonstrate that the factor governing T_(c) is primarily derived from Li-p-hybridized electronic states with ISQ compositions.These electronic states are scattered by low-frequency phonons arising from mixed vibrations of Li and Al affected by ISQs to enhance electron–phonon coupling.Our study largely expands the research scope of electrides,provides new insight for understanding phase transitions,and elucidates the effects of ISQs on superconducting behavior.
基金supported by the Research Project on Strengthening the Construction of an Important Ecological Security Barrier in Northern China by Higher Education Institutions in the Inner Mongolia Autonomous Region(STAQZX202313)the Inner Mongolia Autonomous Region Education Science‘14th Five-Year Plan’2024 Annual Research Project(NGJGH2024635).
文摘Vacancy defects,as fundamental disruptions in metallic lattices,play an important role in shaping the mechanical and electronic properties of aluminum crystals.However,the influence of vacancy position under coupled thermomechanical fields remains insufficiently understood.In this study,transmission and scanning electron microscopy were employed to observe dislocation structures and grain boundary heterogeneities in processed aluminum alloys,suggesting stress concentrations and microstructural inhomogeneities associated with vacancy accumulation.To complement these observations,first-principles calculations and molecular dynamics simulations were conducted for seven single-vacancy configurations in face-centered cubic aluminum.The stress response,total energy,density of states(DOS),and differential charge density were examined under varying compressive strain(ε=0–0.1)and temperature(0–600 K).The results indicate that face-centered vacancies tend to reduce mechanical strength and perturb electronic states near the Fermi level,whereas corner and edge vacancies appear to have weaker effects.Elevated temperatures may partially restore electronic uniformity through thermal excitation.Overall,these findings suggest that vacancy position exerts a critical but position-dependent influence on coupled structure-property relationships,offering theoretical insights and preliminary experimental support for defect-engineered aluminum alloy design.
基金supported by the financial aid from the National Natural Science Foundation of China (No. 22271273)International Partnership Program of Chinese Academy of Sciences (No. 121522KYSB20190022)。
文摘Self-trapping excitons(STEs) emission in metal halides has been a matter of interest, correlating with the strength of electron-phonon coupling in the lattice, which are usually caused by ions with ns~2 electronic structure. In this work, Sb^(3+)/Te^(4+)ions doped Zn-based halide single crystals(SCs) with two STEs emissions have been synthesized and the possibility of its anti-counterfeiting application was explored.Further, the relationship between the strength of electron-phonon coupling and photoluminescence quantum yields(PLQYs) for STEs in a series of metal halides has been studied. And the semi-empirical range of the Huang-Rhys factors(S) for metal halides with excellent photoluminescence(PL) property has been summarized. This work provides ideas for further research into the relationship between luminescence performance and electron-phonon coupling of metal halides, and also provides a reference for designing the metal halides with high PLQYs.
基金supported by the National Natural Science Foundation of China(Nos.12404045 and 52371148)the National Key R&D Program of China(No.2018YFC 1900500)+1 种基金the Foundation of Chongqing Normal University,China(No.23XLB015)the Science and Technology Research Program of Chongqing Municipal Education Commission,China(No.KJQN-202400553)。
文摘Metal vanadates garner significant interest because of their exceptional potential for use in diverse practical applications,which stems from their unique framework structures,bond strength heterogeneities,and strong O^(2-)-V^(5+)charge-transfer bands.However,their optoelectronic properties have not yet been sufficiently explored.In this study,we synthesized three high-purity calcium vanadate compounds(Ca V_(2)O_(6),Ca_(2)V_(2)O_(7),and Ca_(3)V_(2)O_(8))and comprehensively investigated their optoelectronic properties via first-principles calculations and experimental characterizations.Ca V_(2)O_(6),Ca_(2)V_(2)O_(7),and Ca_(3)V_(2)O_(8) are indirect band gap semiconductors with band gaps of 2.5-3.4 e V.A comparative analysis between density functional theory(DFT)and DFT+U(local Coulomb interaction,U)calculations revealed that standard DFT was sufficient to accurately describe the lattice parameters and band gaps of these vanadates.Further luminescence studies revealed significant photo-and electro-luminescence properties within the visible light spectrum.Notably,the luminescence intensity of CaV_(2)O_(6) exhibited a remarkable 10-fold enhancement under a modest pressure of only 0.88 GPa,underscoring its exceptional potential for use in pressure-tunable optical applications.These findings provide deeper insight into the electronic structures and optical behaviors of vanadates and highlight their potential as strong candidates for application in phosphor materials and optoelectronic devices.
文摘This study investigates the structural,electronic,vibrational,and mechanical properties of cubic InTe using density functional theory and density functional perturbation theory.The results reveal the metallic character of cubic InTe,as indicated by its electronic structure and density of states.The dynamic stability of the material is confirmed by phonon dispersion analysis,with no imaginary frequencies observed.The Debye temperature(172.276 K)and melting temperature(1092.832 K)suggest excellent thermal resistance.A shear modulus of 18.20 GPa,Poisson’s ratio of 0.343,and Pugh’s ratio([Math Processing Error])of 2.87 support mechanical stability and indicate ductility.Isotropic dielectric properties,with Born effective charges of−3.768 for both In and Te atoms,highlight potential ferroelectric applications.These findings emphasize InTe’s suitability for electronic and construction applications.
基金support from the National Key Research and Development Program of China(No.2022YFB3705600)the Shanghai Science and Technology Innovation Action Plan(No.22SQBS00600).
文摘Electron beam powder bed fusion(EB-PBF)offers a promising route for producing Ti_(6)Al_(4)V alloys with tailored microstructures and superior mechanical properties.Herein,EB-PBF produced nearly fully dense Ti 6Al 4V alloys(≥98.5%)with basketweave microstructures containing fine equilibriumαlamellae,different from typicalα′acicular observed in materials produced via laser-PBF.The as-printed horizontal material has a yield strength(YS)of 992 MPa,an ultimate tensile strength(UTS)of 1053 MPa,and a fracture strain(ε)of 10.9%.Meanwhile,the as-printed longitudinal material shows inferior mechanical properties(YS of 934 MPa,UTS of 979 MPa,andεof 2.4%).The horizontal and longitudinal samples show notable hysteresis loops in the loading unloading reloading curves,indicating substantial heterogeneous-induced strengthening.Flow stress,back stress,and effective stress increase with increasing strain,where back stress is comparable to effective stress during the overall deformation.Furthermore,a monotonically decreased strain hardening rate with increasing strain can be attributed to dislocation activities,whose failure is related to the strain localization at theαlamellae boundary.
基金supported by the National Key Research and Development Program of China(No.2023YFC2810700)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2021193)the Science and Technology Cooperation Project between Jilin Province and Chinese Academy of Sciences(No.2024SYHZ0032).
文摘This study analyzed through-thickness distribution of residual stress in a 106 mm ultra-thick TC4 titanium alloy electron beam welded(EBW)joint after post weld heat treatment(PWHT)using X-ray diffraction(XRD)and deep-hole drilling(DHD)methods,and investigated the microstructure and mechanical properties.During the PWHT at 600℃,a phase transformation(β→α)occurred in the EBW joint and affected the residual stress distribution and mechanical properties.The surface residual stress was mainly compressive stress,while the internal residual stress was mainly tensile stress in the welded joint.For the as-welded joint,the absolute value of surface residual stress was higher than the absolute value of internal residual stress.After PWHT,the residual stress in the treated joint was substantially reduced compared to the as-welded joint,particularly the surface stress,which relieved from−425 to−90 MPa.However,the residual stress relief effect had minimal positive impact on the internal region at 600℃.PWHT resulted in a shift of the joint fracture location from the fusion zone(FZ)to the base metal(BM),and therefore exerted no noticeable effect on the joint strength,but increased the joint elongation significantly.This study provides valuable insights into the regulation of residual stress distribution of ultra-thick titanium alloy plates.
基金supported by the National Natural Science Foundation of China(No.21927814)the National Key Research and Development Program of China(Nos.2019YFA0405600,2019YFA0706900,2021YFA1200104,2022YFC3400500)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDB0540200,XDB37040201)Plans for Major Provincial Science&Technology Projects(No.202303a07020004)the Youth Innovation Promotion Association,CAS(No.2022455)。
文摘Liquid-liquid phase separation(LLPS)of proteins and nucleic acids is a common phenomenon in cells that underlies the formation of membraneless organelles.Although the macroscopic behavior of biomolecular coacervates has been elucidated by microscopy,the detailed dynamic properties of proteins/peptides during the LLPS process remain poorly characterized.Here,site-directed spin labeling-electron paramagnetic resonance(SDSL-EPR)spectroscopy was employed to characterize the dynamic properties of a minimal model LLPS system consisting of positively charged peptides and RNA.The degree of phase separation,indicated by broadening of the EPR spectrum of the spin-labeled peptide due to slow molecular tumbling,was monitored by EPR.In addition,three distinct populations with varying molecular motion during LLPS,featuring different spectral lineshapes,were identified.These populations included a fast motion component(Ⅰ),a slower motion component(Ⅱ)associated with peptides in the dispersed phase and an immobile component(Ⅲ)observed in the dense phase.With gradual titration of the peptides to RNA,the EPR spectrum gradually shifted,refiecting changes in the populations of the components.Together,SDSL-EPR method not only provides new insights into the dynamic behavior of biomolecules during LLPS,but also offers a sensitive method for biomolecular phase separation processes at the molecular level.
基金supported by the National Natural Science Foundation of China(Nos.92166105 and 52005053)High-Tech Industry Science and Technology Innovation Leading Program of Hunan Province(No.2020GK2085)the Science and Technology Innovation Program of Hunan Province(No.2021RC3096).
文摘(NbZrHfTi)C high-entropy ceramics,as an emerging class of ultra-high-temperature materials,have garnered significant interest due to their unique multi-principal-element crystal structure and exceptional hightemperature properties.This study systematically investigates the mechanical properties of(NbZrHfTi)C high-entropy ceramics by employing first-principles density functional theory,combined with the Debye-Grüneisen model,to explore the variations in their thermophysical properties with temperature(0–2000 K)and pressure(0–30 GPa).Thermodynamically,the calculated mixing enthalpy and Gibbs free energy confirm the feasibility of forming a stable single-phase solid solution in(NbZrHfTi)C.The calculated results of the elastic stiffness constant indicate that the material meets the mechanical stability criteria of the cubic crystal system,further confirming the structural stability.Through evaluation of key mechanical parameters—bulk modulus,shear modulus,Young’s modulus,and Poisson’s ratio—we provide comprehensive insight into the macro-mechanical behaviour of the material and its correlation with the underlying microstructure.Notably,compared to traditional binary carbides and their average properties,(NbZrHfTi)C exhibits higher Vickers hardness(Approximately 28.5 GPa)and fracture toughness(Approximately 3.4 MPa⋅m^(1/2)),which can be primarily attributed to the lattice distortion and solid-solution strengthening mechanism.The study also utilizes the quasi-harmonic approximation method to predict the material’s thermophysical properties,including Debye temperature(initial value around 563 K),thermal expansion coefficient(approximately 8.9×10^(−6) K−1 at 2000 K),and other key parameters such as heat capacity at constant volume.The results show that within the studied pressure and temperature ranges,(NbZrHfTi)C consistently maintains a stable phase structure and good thermomechanical properties.The thermal expansion coefficient increasing with temperature,while heat capacity approaches the Dulong-Petit limit at elevated temperatures.These findings underscore the potential of(NbZrHfTi)C applications in ultra-high temperature thermal protection systems,cutting tool coatings,and nuclear structural materials.
基金National Natural Science Foundation of China(51975286)。
文摘Fe-Mo functionally graded materials(FGMs)with different composition-change rates from 100%304 stainless steel to 100%Mo along the composition gradient direction were prepared by electron beam-directed energy deposition(EB-DED)technique,including three samples with composition mutation of 100%,composition change rate of 10%and 30%.Results show that the composition-change rate significantly affects the microstructure and mechanical properties of the samples.In the sample with abrupt change of composition,the sharp shift in composition between 304 stainless steel and Mo leads to a great difference in the microstructure and hardness near the interface between the two materials.With the increase in the number of gradient layers,the composition changes continuously along the direction of deposition height,and the microstructure morphology shows a smooth transition from 304 stainless steel to Mo,which is gradually transformed from columnar crystal to dendritic crystal.Elements Fe,Mo,and other major elements transform linearly along the gradient direction,with sufficient interlayer diffusion between the deposited layers,leading to good metallurgical bonding.The smaller the change in composition gradient,the greater the microhardness value along the deposition direction.When the composition gradient is 10%,the gradient layer exhibits higher hardness(940 HV)and excellent resistance to surface abrasion,and the overall compressive properties of the samples are better,with the compressive fracture stress in the top region reaching 750.05±14 MPa.
基金financially supported by the National Natural Science Foundation of China(No.52301050)the Young Elite Scientists Sponsorship Program by the China Association for Science and Technology(No.2022QNRC001)the China Postdoctoral Science Foundation(No.2023M741701).
文摘Titanium aluminide(TiAl)alloys,known for their light weight and high specific strength,hold promising potential for aerospace applications.Recent studies have focused on improving their properties through composite strengthening.An in situ synthesized Ti_(5)Si_(3)-reinforced TiAl composite with excellent performance was successfully fabricated via a dual-wire electron beam-directed energy deposition(EB-DED)process.The microstructure of the as-deposited Ti_(5)Si_(3)/TiAl composite consisted of primary Ti_(5)Si_(3)rods,eutectic Ti_(5)Si_(3)needles,and lamellar TiAl+Ti_(3)Al structures.The phase transformation during the EB-DED process was L→Ti_(5)Si_(3)+L→Ti_(5)Si_(3)+(α+Ti_(5)Si_(3))Eutectic→Ti_(5)Si_(3)+(Ti3Al+TiAl)Eutectoid.The expanded Blackburn orientation relationships among the ternary phases emerged from the eutectic reaction of L→α+Ti_(5)Si_(3)with an undercooling exceeding 136°C and the subsequent eutectoid reaction with ordering transformation and were expressed as<1120>TisAl//<10I0>Ti_(5)Si_(3)//<110]Ti_(3)Al and{0001}TiзA//{0001}Ti_(5)Si_(3)//{111}TiAl.The Ti_(5)Si_(3)phase had a greater hardness than did the lamellar structures and enhanced the mechanical properties of the matrix.The compressive yield strengths at room temperature and 750°C were 1221±51 and 1034±34 MPa,respectively,whereas the tensile yield strength was 347.4±12.7 MPa at 950°C,surpassing those of other TiAl alloys.The calculated strength with different strengthening mechanisms was 1056.4 MPa,and the greatest improvement in strength was attributed to the decreased interlamellar spacing.This work provides critical insight into the design of TiAl composites with superior mechanical properties and aids in understanding the microstructural evolution of as-deposited Ti_(5)Si_(3)/TiAl composites.
文摘Nitrogen doping in chemical vapor deposition-derived ultrananocrystalline diamond(UNCD)films in-creases the electronic conductivity,yet its microstructural effects on electron transport are insufficiently understood.We investigated the formation of nitrogen-induced diaph-ite structures(hybrid diamond-graphite phases)and their role in changing the conductivity.Nitrogen doping in a hy-drogen-rich plasma environment promotes the emergence of unique sp^(3)-sp^(2)bonding interfaces,where diamond grains are covalently integrated with graphitic domains,facilitating a structure-driven electronic transition.High-resolution transmis-sion electron microscopy and selected area electron diffraction reveal five-fold,six-fold and twelve-fold symmetries,along with an atypical{200}crystallographic reflection,confirming diaphite formation in 5%and 10%N-doped UNCD films,while high-er doping levels(15%and 20%)result in extensive graphitization.Raman spectroscopy tracks the evolution of sp^(2)bonding with increasing nitrogen content,while atomic force microscopy and X-ray diffraction indicate a consistent diamond grain size of~8 nm.Cryogenic electronic transport measurements reveal a conductivity increase from 8.72 to 708 S/cm as the nitrogen dop-ing level increases from 5%to 20%,which is attributed to defect-mediated carrier transport and 3D weak localization.The res-ulting conductivity is three orders of magnitude higher than previously reported.These findings establish a direct correlation between diaphite structural polymorphism and tunable electronic properties in nitrogen-doped UNCD films,offering new ways for defect-engineering diamond-based electronic materials.
基金supported by the Pazy Foundation of the Israel Atomic Energy Commission and the Israeli Council of Higher Education(Grant No.322/20)。
文摘Only a few studies have reported the efects of electrochemical hydrogenation on the tensile mechanical properties of additively manufactured Ti–6Al–4V alloy,in all of them the alloy was processed by laser powder-bed fusion.Furthermore,the efects of either hot isostatic pressing(HIP)or heat treatment(HT)post-treatments on the mechanical properties were not reported.Here,the Young’s modulus,ultimate tensile stress,and uniform(homogeneous)strain of as-built electron beam melted(EBM)Ti–6Al–4V alloys were studied using small tensile specimens before and after electrochemical hydrogenation,as well as before and after secondary processes of HIP at 920℃ and HT at 1000℃.The tensile properties of all hydrogenated alloys were signifcantly degraded compared to their non-hydrogenated counterparts.The yield stress could not be determined for all hydrogenated alloys,as failure occurred at a strain below 0.2%ofset.The uniform strain of the hydrogenated alloys was less than 1%,compared to 1%–5%for the non-hydrogenated alloys.The fracture mode of the hydrogenated alloys after HIP and HT revealed cleavage fracture,indicating increased brittleness.In the as-built hydrogenated alloy,the fracture mode varied with location:brittle fracture occurred near the surface due to the formation of a hydride layer,while a more ductile fracture with dimples was observed below this layer.
基金Funded by the National Natural Science Foundation of China(No.U1904612)the Natural Science Foundation of Henan Province(No.222300420506)。
文摘The structural,relative stability,and electronic properties of two-dimensional AsP_(2)X_(6)(X=S,Se)were predicted and studied using the particle-swarm optimization method and first principles calculations.We proposed two low energy structures with P312 and P-31m phases,both of which the structures are hexagonal in shape and show non-centrosymmetry for the P312 phase and centrosymmetry for the P-31m phase.According to our results,two structural phases are found to be stable thermally and dynamically.The P312 phase of AsP_(2)X_(6)(X=S,Se)are indirect semiconductors with band gaps of 2.44 eV(AsP2S6)and 2.18 eV(AsP2Se6)at the HSE06 level,and their absorption coefficients are predicted to reach the order of 10^(5)cm^(-1)from visible light to ultraviolet region,but the main absorption is manly in the ultraviolet region.The P-31m phase of AsP_(2)X_(6)(X=S,Se)exhibits metal character with the Fermi surface mainly occupied by the p orbital of S/Se.Remarkably,estimated by first principles calculations,the P-31m AsP2S6 is found to be an intrinsic phonon-mediated superconductor with a relatively high critical superconducting temperature of about 13.4 K,and the P-31m AsP2Se6 only has a superconducting temperature of 1.4 K,which suggest that the P-31m AsP2S6 may be a good candidate for a nanoscale superconductor.
基金Funded by the National Key R&D Program of China(No.2021YFB3802300)the Foundation of National Key Laboratory of Shock Wave and Detonation Physics(No.JCKYS2022212004)the National Natural Science Foundation of China(No.52171045),and the Joint Fund(No.8091B022108)。
文摘The effects of pressure on the structural stability,elasticity,electronic properties,and thermodynamic properties of Al,Al_(3)Cu,Al_(2)Cu,Al_(4)Cu_(9),AlCu_(3),and Cu were investigated using first-principles calculations.The experimental results indicate that the calculated equilibrium lattice constant,elastic constant,and elastic modulus agree with both theoretical and experimental data at 0 GPa.The Young's modulus,bulk modulus,and shear modulus increase with increasing pressure.The influence of pressure on mechanical properties is explained from a chemical bond perspective.By employing the quasi-harmonic approximation model of phonon calculation,the temperature and pressure dependence of thermodynamic parameters in the range of 0 to 800 K and 0 to 100 GPa are determined.The findings demonstrate that the thermal capacity and coefficient of thermal expansion increase with increasing temperature and decrease with increasing pressure.This study provides fundamental data and support for experimental investigations and further theoretical research on the properties of aluminum-copper intermetallic compounds.
文摘Density functional theory(DFT)studies were performed on the lattice parameters,electronic band structure,and optical constants under pressure up to 20 GPa in order to obtain insight into the electronic and optical properties of LiZnAs.The calculated results show LiZnAs is a semiconductor with a direct gap of 0.86 eV,which is smaller than the experimental value 1.1 eV.It also indicates that the structural parameters such as lattice parameters and cell volume show inverse relation to the pressure and shows smooth decreasing behavior from 0 to 20 GPa.Meanwhile,the pressure dependence of the electronic band structure,density of states and partial density of states of LiZnAs up to 20 GPa were presented.And we found that the band gap increased with the pressure.Moreover,the evolution of the dielectric function,absorption coefficient a(w),reflectivity R(w),the refractive index n(w),and the extinction coefficient k(w)of LiZnAs under pressure were presented.According to our work,we found that the optical properties of LiZnAs undergo a blue shift with increasing pressure.These results suggest technological applications of such materials in extreme environments.
