In order to calculate the multipoles in real materials with considerable intersite Coulomb interaction V,we develop a self-consistent program which starts from the frst-principles calculations to solve the tight-bindi...In order to calculate the multipoles in real materials with considerable intersite Coulomb interaction V,we develop a self-consistent program which starts from the frst-principles calculations to solve the tight-binding Hamiltonian including onsite Coulomb repulsion U,V,and spin-orbital couplingλ.The program is applied to Ba_(2)MgReO_(6)to fgure out the mechanism of structural instability and magnetic ordering.A comprehensive quadrupole phase diagram versus U and V withλ=0.28 eV is calculated.Our results demonstrate that the easy-plane anisotropy and the intersite Coulomb repulsion V must be considered to remove the orbital frustration.The increase of V to>20 meV would arrange quadrupole Q_(x^(2)-y^(2))antiparallelly,accompanied by small parallel Q_(3z)^(2)-r^(2),and stabilize Ba_(2)MgReO_(6)into the body-centered tetragonal structure.Such antiparallel Q_(x^(2)-y^(2))provides a new mechanism for the Dzyaloshinskii-Moriya interaction and gives rise to the canted antiferromagnetic(CAF)state along the[110]axis.Moreover,sizable octupoles such as O_(21)^(31),O_(21)^(33),O_(21)^(34)and O_(21)^(36)are discovered for the frst time in the CAF state.Our study not only provides a comprehensive understanding of the experimental results in Ba_(2)MgReO_(6),but also serves as a general and useful tool for the study of multipole physics in 5d compounds.展开更多
Alloying transition metals with Pt is an effective strategy for optimizing Pt-based catalysts toward the oxygen reduction reaction(ORR).Atomic ordered intermetallic compounds(IMC)provide unique electronic and geometri...Alloying transition metals with Pt is an effective strategy for optimizing Pt-based catalysts toward the oxygen reduction reaction(ORR).Atomic ordered intermetallic compounds(IMC)provide unique electronic and geometrical effects as well as stronger intermetallic interactions due to the ordered arrangement of metal atoms,thus exhibiting superior electrocata-lytic activity and durability.However,quantitatively analyzing the ordering degree of IMC and exploring the correlation between the ordering degree and ORR activity remains extremely challenging.Herein,a series of ternary Pt_(2)NiCo interme-tallic catalysts(o-Pt_(2)NiCo)with different ordering degree were synthesized by annealing temperature modulation.Among them,the o-Pt_(2)NiCo which annealed at 800℃for two hours exhibits the highest ordering degree and the optimal ORR ac-tivity,which the mass activity of o-Pt_(2)NiCo is 1.8 times and 2.8 times higher than that of disordered Pt_(2)NiCo alloy and Pt/C.Furthermore,the o-Pt_(2)NiCo still maintains 70.8%mass activity after 30,000 potential cycles.Additionally,the ORR activity test results for Pt_(2)NiCo IMC with different ordering degree also provide a positive correlation between the ordering degree and ORR activity.This work provides a prospective design direction for ternary Pt-based electrocatalysts.展开更多
Martensitic transformation plays a pivotal role in strengthening and hardening of steels,yet an accu-rate interatomic potential for a comprehensive description of the martensitic phase formation in Fe-C alloys is lack...Martensitic transformation plays a pivotal role in strengthening and hardening of steels,yet an accu-rate interatomic potential for a comprehensive description of the martensitic phase formation in Fe-C alloys is lacking.Herein,we developed a deep learning-based interatomic potential to perform molecu-lar dynamics(MD)simulations to study the martensitic phase transformation across a range of carbon(C)concentrations.The results revealed that an increased C concentration leads to a suppressed phase boundary movement and a decelerated phase transformation rate.To overcome the timescale limitations inherent in MD simulations,metadynamics sampling was employed to accelerate the simulations of C dif-fusion.We found that C atoms tend to cluster at distances equivalent to the lattice parameter of Fe with the same sublattice occupation,leading to local lattice tetragonality.Such C-ordered structures effectively inhibit dislocation movement and enhance strength.The stress field induced by dislocations facilitates a higher degree of ordering,and the formation of C-ordered structures was identified as a potentially cru-cial strengthening mechanism for martensitic steels.The consistency between our simulation results and reported experimental observations underscores the effectiveness of the developed DP model in simu-lating martensitic phase transformation in Fe-C alloys,providing detailed insights into the mechanisms underlying this process.This work not only advances the understanding of martensitic phase transforma-tions in Fe-C alloys but also establishes a powerful computational framework for designing steels with optimized mechanical properties through the precise control of carbon ordering and dislocation behavior.展开更多
Medium-entropy alloys(MEAs)have garnered significant interest due to their unique mechanical prop-erties,but phase instabilities such as the formation of brittle sigma(σ)phase during annealing pose challenges to thei...Medium-entropy alloys(MEAs)have garnered significant interest due to their unique mechanical prop-erties,but phase instabilities such as the formation of brittle sigma(σ)phase during annealing pose challenges to their practical application.This study investigates the microstructural evolution and me-chanical behavior of an 80%cold-rolled Fe_(45)Co_(35)Cr_(10)V_(10)MEA that was isochronally annealed between 100℃ and 900℃ for 300 s and characterized using hardness indentations,in-situ X-ray diffraction,and thermodynamic calculations,with high-resolution electron microscopy detailing microstructural evo-lution at 625℃,675℃,and 725℃.The results show increases in Vickers hardness between 500℃ and 625℃,attributed to the nucleation of a Cr-and V-rich sigma(σ)phase,primarily at the bcc grain boundaries.Beyond 625℃,the hardness decreased due toσ-phase dissolution,recovery of bcc and fcc phases,bcc→fcc phase reversion,and recrystallization of the reverted fcc phase.Scanning-transmission electron microscopy and transmission Kikuchi diffraction revealed a Kurdjumov-Sachs orientation rela-tionship(OR)at 675℃ and a near Nishiyama-Wassermann OR at 725℃ for bcc-fcc interfaces,whereas bcc-σand fcc-σinterfaces showed no dominant OR.In addition toσphase,two types of bcc phase were identified at 625℃.Type 1 bcc initially retained a near-nominal composition and a disordered crystal structure from deformation-induced bcc martensite but gradually became Fe-enriched and Cr-and V-depleted up to 725℃.In contrast,Type 2 bcc phase was Fe-depleted and Co-enriched at 625℃ but dis-appeared at 675℃,coinciding with the onset of bcc→fcc phase reversion.This phase also exhibited B2-like chemical short-range ordering,with alternating FeCo-rich and CrV-rich domains.This study provides insights into the complex phase transformation occurring between 500℃ and 725℃ in a Fe_(45)Co_(35)Cr_(10)V_(10)MEA,which can be leveraged to design alloys with optimized mechanical properties for practical appli-cations.展开更多
In order to understand the influence of ordering behaviors on the thermodynamic and mechanical properties of multi-principal element alloys(MPEAs),the temperature-dependent thermodynamic properties and mechanical prop...In order to understand the influence of ordering behaviors on the thermodynamic and mechanical properties of multi-principal element alloys(MPEAs),the temperature-dependent thermodynamic properties and mechanical properties of FCC_CoNiV MPEAs were comparatively predicted,where the alloys were modeled as the ordered configurations based on our previously predicted site occupying fractions(SOFs),as well as disordered configuration based on traditional special quasi-random structure(SQS).The ordering behavior not only improves the thermodynamic stability of the structure,but also increases the elastic properties and Vickers hardness.For example,at 973 K,the predicted bulk modulus(B),shear modulus(G),Young’s modulus(E),and Vickers hardness(HV)of FCC_CoNiV MPEA based on SOFs configuration are 187.82,79.03,207.93,and 7.58 GPa,respectively,while the corresponded data are 172.58,57.45,155.14,and 4.64 GPa for the SQS configuration,respectively.The Vickers hardness predicted based on SOFs agrees considerably well with the available experimental data,while it is underestimated obviously based on SQS.展开更多
Polar semiconductors,particularly the emerging polar two-dimensional(2D)halide perovskites,have motivated immense interest in diverse photoelectronic devices due to their distinguishing polarizationgenerated photoelec...Polar semiconductors,particularly the emerging polar two-dimensional(2D)halide perovskites,have motivated immense interest in diverse photoelectronic devices due to their distinguishing polarizationgenerated photoelectric effects.However,the constraints on the organic cation's choice are still subject to limitations of polar 2D halide perovskites due to the size of the inorganic pocket between adjacent corner-sharing octahedra.Herein,a mixed spacer cation ordering strategy is employed to assemble a polar 2D halide perovskite NMAMAPb Br_(4)(NMPB,NMA is N-methylbenzene ammonium,MA is methylammonium)with alternating cation in the interlayer space.Driven by the incorporation of a second MA cation,the perovskite layer transformed from a 2D Pb_(7)Br_(24)anionic network with corner-and face-sharing octahedra to a flat 2D PbBr_(4)perovskite networks only with corner-sharing octahedra.In the crystal structure of NMPB,the asymmetric hydrogen-bonding interactions between ordered mixed-spacer cations and 2D perovskite layers give rise to a second harmonic generation response and a large polarization of 1.3μC/cm^(2).More intriguingly,the ordered 2D perovskite networks endow NMPB with excellent self-powered polarization-sensitive detection performance,showing a considerable polarization-related dichroism ratio up to 1.87.The reconstruction of an inorganic framework within a crystal through mixed cation ordering offers a new synthetic tool for templating perovskite lattices with controlled properties,overcoming limitations of conventional cation choice.展开更多
L1_(0)-FePt nanoparticles(NPs)are urgently anticipated because of their promising applications.However,the preparation of the NPs with both of high ordering degree and super-fine size is still a challenge.Inspired by ...L1_(0)-FePt nanoparticles(NPs)are urgently anticipated because of their promising applications.However,the preparation of the NPs with both of high ordering degree and super-fine size is still a challenge.Inspired by recent studies on the effect of vacancy defects on structural ordering,we proposed an intentional vacancy defect design strategy for directly synthesizing highly ordered FePt NPs.In the present work,we used the first-principle calculations to investigate the influence of doping typical elements(Cu,Ag,and Pb)on the vacancy formation energy(E_(vac))of FePt NPs.The vacancy defects were effectively formed by introducing elements of larger atomic radii and higher propensity for segregation into the FePt lattice,facilitating the diffusion of Fe and Pt atoms.The Pb doping showed remarkable efficacy in promoting the ordering transition.Experimentally,wet-chemical synthesis confirmed the success of the proposed strategy in achieving highly ordered L1_(0)-FePt NPs with exceptional magnetic properties and super-fine size(ordering degree of 0.896,impressive coercivity of 21.74 kOe,and small particle size of 9.02 nm).Additionally,we have deduced a diffusion model elucidating the formation process of the ordered FePt NPs,focusing on the migration of Pb atoms from the center to the surface of the particles.This migration is demonstrated to generate more vacancies and promote the transition to the ordered L1_(0)-FePt phase.The findings of this research offer valuable insights into synthesizing highly ordered and ultrafine L1_(0)-type nanomaterials.展开更多
1.Introduction Multi-principal element alloys(MPEAs),with compositions in the central region of the multicomponent phase diagram,have been dubbed"high-entropy alloys"(HEAs)in recent years[1-11].A more genera...1.Introduction Multi-principal element alloys(MPEAs),with compositions in the central region of the multicomponent phase diagram,have been dubbed"high-entropy alloys"(HEAs)in recent years[1-11].A more general term currently accepted by the community for these MPEAs is complex concentrated alloys or compositionally complex alloys(CCAs)[12].These alloys are usually based on single-phase multi-principal element solid solutions,with no need or possibility to distinguish which species constitutes the solvent and which ones are solutes.This Viewpoint and Perspective article focuses on a salient feature in the internal structure of MPEAs,different from traditional metals and solvent-(dilute)solute solutions.Specifically,the unusual trait to be highlighted for these heavily concentrated solutions is their inherent chemical inhomogeneity on the nanoscale,in terms of the high propensity for compositional fluctuation and local chemical order.展开更多
The ground-state magnetic ordering of uranium mononitride(UN)remains a contentious topic due to the unexpected lack of crystallographic distortion in the traditionally accepted 1k antiferromagnetic(AFM)state.This disc...The ground-state magnetic ordering of uranium mononitride(UN)remains a contentious topic due to the unexpected lack of crystallographic distortion in the traditionally accepted 1k antiferromagnetic(AFM)state.This discrepancy casts doubt on the validity of the 1k magnetic ordering of UN.Here,we investigate the crystal structure,high-pressure phase transitions,and dynamical and mechanical properties of UN in its 1k and 3k AFM ground states using density functional theory(DFT).Our results reveal that the undistorted 3k AFM state of Fm3m within the DFT+U+SOC scheme is more consistent with experimental results.The Hubbard U and spin-orbit coupling(SOC)are critical for accurately capturing the crystal structure,high-pressure structural phase transition,and dynamical properties of UN.In addition,we have identified a new high-pressure magnetic phase transition from the nonmagnetic(NM)phase of R3m to the P63/mmc AFM state.Electronic structure analysis reveals that the magnetic ordering in the ground state is primarily linked to variations in partial 5f orbital distributions.Our calculations provide valuable theoretical insights into the complex magnetic structures of a typical strongly correlated uranium-based compound.Moreover,they provide a framework for understanding other similar actinide systems.展开更多
Full-manganese(Mn)Li-rich materials have gained attention owing to the limited availability of cobalt-or nickel-based cathodes commonly used in batteries,which greatly restricts their potential for large-scale applica...Full-manganese(Mn)Li-rich materials have gained attention owing to the limited availability of cobalt-or nickel-based cathodes commonly used in batteries,which greatly restricts their potential for large-scale application.However,their practical implementation is hindered by the rapid voltage/capacity decay during cycling and the long-standing problem of redox kinetics due to their poor ionic conductivity based on the ordered honeycomb structure.In this study,the kinetic and thermodynamic properties of intralayer disordered and ordered Li-rich full-Mn-based cathode materials were compared,demonstrating that the disordered R3m Li_(0.6)[Li_(0.2)Mn_(0.8)]O_(2)(D-LMO)delivers a significant advantage of rate capability over the ordered C2/m Li_(0.6)[Li_(0.2)Mn_(0.8)]O_(2)(O-LMO).Meanwhile,the D-LMO keeps superior capacity retention of up to 99%after 50 cycles under 25 mAg^(-1).In comparsion,the capacity retention of the O-LMO drops to just 70%,and its average discharge voltage is 0.2 V lower than that of the D-LMO.Herein,we conducted systematic density functional theory(DFT)simulations,focusing on the electronic structure modulation governing the voltage platform between the ordered and disordered phases.The ab initio molecular dynamics(AIMD)results indicated that the energy of the intralayer disordered structure fluctuates around the equilibrium position without any abrupt drops,demonstrating excellent stability.This study enhances the understanding of intralayer disordered full-Mn Li-rich material and provides insights into the design of low-cost,high-performance cathode materials for Li-ion batteries.展开更多
In this paper by virtue of the technique of integration within an ordered product （IWOP） of operators and the intermediate coordinate-momentum representation in quantum optics, we derive the normal ordering and anti...In this paper by virtue of the technique of integration within an ordered product （IWOP） of operators and the intermediate coordinate-momentum representation in quantum optics, we derive the normal ordering and antinormal ordering products of the operator （fQ＋gP）n when n is an arbitrary integer. These products are very useful in calculating their matrix elements and expectation values and obtaining some useful mathematical formulae. Finally, the applications of some new identities are given.展开更多
The ultrasonic, magnetic and transport properties of Nd0.5Ca0.5Mn1-xAlxO3 （x=0, 0.03） were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0.5Ca0.5MnO3 undergoes a...The ultrasonic, magnetic and transport properties of Nd0.5Ca0.5Mn1-xAlxO3 （x=0, 0.03） were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0.5Ca0.5MnO3 undergoes a charge ordering transition at TCO-257 K. An obvious softening of the longitudinal sound velocity above TCO and a dramatic stiffening below Too accompanied by an attenuation peak were observed. These features imply a strong electron phonom interaction via the Jahn-Teller effect iu the sample, Another broad attenuation peak was observed at around Tp-80 K. This anomaly is attributed to the phase separtion between the antiferromagnetic （AFM） and paramagnetic （PM） phases and gives a direct evidence for spin-phonon coupling in the compound. For the x=0.03 sample, both the minimum of sound velocity and attenuation peaks shift to a lower temperature. The results indicate that the charge ordering and CE-type AFM state in Nd0.5Ca0.5MnO3 are both partially suppressed by replacing Mn with A1.展开更多
A series of TiAl+Nb alloys with various Nb contents has been employed to explore phase relationship and the evolution of microstructure.A new ordered γ derivative (γ1) has been observed in the alloy containing 20 at...A series of TiAl+Nb alloys with various Nb contents has been employed to explore phase relationship and the evolution of microstructure.A new ordered γ derivative (γ1) has been observed in the alloy containing 20 at% Nb.The additional diffraction spots added to the diffraction pattern of L10 (TiAl) structure have been found in the alloy containing Nb up to 11 at% in terms of further ordering.The transformation from L10 (TiAl) structure to the further ordering phase,γ1,is a continuous ordering process with the substitution of Nb atoms for Ti atoms in alloys with over-stoichiometric Al content of TiAl.The possible transformtion characterzation has been discussed.展开更多
The first-principles calculations were used to explore the tunable electronic structure in DyNiO_(3)(DNO)under the effects of the biaxial compressive and tensile strains.We explored how the biaxial strain tunes the or...The first-principles calculations were used to explore the tunable electronic structure in DyNiO_(3)(DNO)under the effects of the biaxial compressive and tensile strains.We explored how the biaxial strain tunes the orbital hybridization and influences the charge and orbital ordering states.We found that breathing mode and Jahn–Teller distortion play a primary role in charge ordering state and orbital ordering state,respectively.Additionally,the calculated results revealed that the biaxial strain has the ability to manipulate the phase competition between the two states.A phase transition point has been found under tensile train.If the biaxial train is larger than the point,the system favors orbital ordering state.If the strain is smaller than the point,the system is in charge ordering state favorably.展开更多
This paper establishes an ordering contraction mapping principle for increasing mapping in partial ordering metric spaces, and applies it to prove the existence and uniqueness of fixed point for some nonlinear operato...This paper establishes an ordering contraction mapping principle for increasing mapping in partial ordering metric spaces, and applies it to prove the existence and uniqueness of fixed point for some nonlinear operators controlled by a linear operator and phi-concave operator in a partial ordering Banach space. Therefore, this two results are unified.展开更多
Taking experimental path on disordering AuCuI（AAuCu8A4）composed of A Au8 and ACu4 stem alloy genes as an example, three discoveries and a method were presented. The ability of Au Cu I（AAu Cu8 A4）to keep structure ...Taking experimental path on disordering AuCuI（AAuCu8A4）composed of A Au8 and ACu4 stem alloy genes as an example, three discoveries and a method were presented. The ability of Au Cu I（AAu Cu8 A4）to keep structure stabilization against changing temperature is attributed to the fact that the AAu8 and ACu4 potential well depths greatly surpass their vibration energies, which leads to the subequilibrium of experimental path. A new atom movement mechanism of AuCuI（AAuACu84）to change structure for suiting variation in temperature is the resonance activating-synchro alternating of alloy genes, which leads to heterogeneous and successive subequilibrium transitions. There exists jumping order degree, which leads to the existence of jumping Tj-temperature and an unexpected so-called ＂retro-effect＂ about jumping temperature retrograde shift to lower temperatures upon the increasing heating rate. A set of subequilibrium holographic network path charts were obtained by the experimental mixed enthalpy path method.展开更多
Rational planning of spares configuration project is an effective approach to improve equipment availability as well as reduce life cycle cost （LCC）. With an analysis of various impacts on support system, the spares...Rational planning of spares configuration project is an effective approach to improve equipment availability as well as reduce life cycle cost （LCC）. With an analysis of various impacts on support system, the spares demand rate forecast model is constructed. According to systemic analysis method, spares support effectiveness evaluation indicators system is built, and then, initial spares configuration and optimization method is researched. To the issue of discarding and con-sumption for incomplete repairable items, its expected backorders function is approximated by Laplace demand distribution. Combining the （s-1, s） and （R, Q） inventory policy, the spares resup-ply model is established under the batch ordering policy based on inventory state, and the optimi-zation analysis flow for spares configuration is proposed. Through application on shipborne equipment spares configuration, the given scenarios are analyzed under two constraint targets：one is the support effectiveness, and the other is the spares cost. Analysis reveals that the result is consistent with practical regulation;therefore, the model＇s correctness, method＇s validity as well as optimization project＇s rationality are proved to a certain extent.展开更多
In this letter,we briefly summarize experimental and theoretical findings of fo rmation and characterization of short-range orderings(SROs)as well as their effects on the defo rmation behavior of high-entropy alloys(H...In this letter,we briefly summarize experimental and theoretical findings of fo rmation and characterization of short-range orderings(SROs)as well as their effects on the defo rmation behavior of high-entropy alloys(HEAs).We show that existence of SROs is a common yet key structural feature of HEAs,and tuning the degree of SROs is an effective way for optimizing mechanical properties of HEAs.In additional,the challenges concerning about formation mechanism and characterization of SROs in HEAs are discussed,and future research activities in this regard are also proposed.展开更多
Polycrystalline samples of La0.4Cao.6Mn1-xCrxO3 （x = 0.00, 0.02, 0.04, 0.06） were prepared by the solid state reaction method. The influence of Cr3＋ substitution for Mn3＋ on the magnetic property and charge orderi...Polycrystalline samples of La0.4Cao.6Mn1-xCrxO3 （x = 0.00, 0.02, 0.04, 0.06） were prepared by the solid state reaction method. The influence of Cr3＋ substitution for Mn3＋ on the magnetic property and charge ordering phase of La0.4Ca0.6MnO3 was studied through the measurements of X-ray diffraction （XRD）, magnetization-temperature （M-T） curves and electron spin resonance （ESR） spectra. The experimental results indicate that the mother＇s body of La0.4Ca0.6MnO3 has very complicated magnetic structure, exhibits charge ordering phase at 258 K, and shows long-range strongly correlated charge ordering-antiferromagnetism （CO-AFM） phase from 175 to 50 K. Spin glass state appears when the temperature decreases to about 41 K. When the Cr substitution amount is x = 0.06, the charge ordering phase of the mother＇s body is de-stroyed, because the Cr3＋ substitution for Mn3＋ destroys the spin order of CE-type antiferromagnetism, and thus leads to the melting of charge ordering. It is verified experimentally that the strong coupling between charge order and spin order exists in the charge order system of CE-type antiferromagnetism.展开更多
Nanograined(NG)materials often suffer from low thermal stability owing to the high volume fraction of grain boundaries(GBs).Herein,we investigate the possibility of utilizing local chemical ordering(LCO)for improving ...Nanograined(NG)materials often suffer from low thermal stability owing to the high volume fraction of grain boundaries(GBs).Herein,we investigate the possibility of utilizing local chemical ordering(LCO)for improving the thermal stability of NG FeCoNiCrMn highentropy alloys(HE As).NG HE As with two different grain sizes were considered.Tensile tests and creep test simulations were then performed to reveal the influence of LCO on the mechanical properties and thermal stability of NG HE As.After performing hybrid molecular dynamics and Monte Carlo simulations,Cr atoms were found to accumulate at GBs.By analyzing the atomic structure evolution during the deformation process,we found that the formation of LCO effectively stabilized the GBs and inhibited GB movement.In addition,dislocation nucleation from GBs and dislocation movement was also hindered.The inhibiting effect of LCO on GB movement and dislocation activity is more prominent than in the NG model with smaller grain sizes.The current simulation results suggest a possible strategy for enhancing the thermal stability of NG HEAs for service in a high-temperature environment.展开更多
基金was supported by the National Key Research and Development Program of China(Grant Nos.2024YFA1611200 and 2018YFA0307000)the National Natural Science Foundation of China(Grant Nos.12274154 and 12404182)。
文摘In order to calculate the multipoles in real materials with considerable intersite Coulomb interaction V,we develop a self-consistent program which starts from the frst-principles calculations to solve the tight-binding Hamiltonian including onsite Coulomb repulsion U,V,and spin-orbital couplingλ.The program is applied to Ba_(2)MgReO_(6)to fgure out the mechanism of structural instability and magnetic ordering.A comprehensive quadrupole phase diagram versus U and V withλ=0.28 eV is calculated.Our results demonstrate that the easy-plane anisotropy and the intersite Coulomb repulsion V must be considered to remove the orbital frustration.The increase of V to>20 meV would arrange quadrupole Q_(x^(2)-y^(2))antiparallelly,accompanied by small parallel Q_(3z)^(2)-r^(2),and stabilize Ba_(2)MgReO_(6)into the body-centered tetragonal structure.Such antiparallel Q_(x^(2)-y^(2))provides a new mechanism for the Dzyaloshinskii-Moriya interaction and gives rise to the canted antiferromagnetic(CAF)state along the[110]axis.Moreover,sizable octupoles such as O_(21)^(31),O_(21)^(33),O_(21)^(34)and O_(21)^(36)are discovered for the frst time in the CAF state.Our study not only provides a comprehensive understanding of the experimental results in Ba_(2)MgReO_(6),but also serves as a general and useful tool for the study of multipole physics in 5d compounds.
基金supported by the National Natural Science Foundation(22279036)the Innovation and Talent Recruitment Base of New Energy Chemistry and Device(B21003).
文摘Alloying transition metals with Pt is an effective strategy for optimizing Pt-based catalysts toward the oxygen reduction reaction(ORR).Atomic ordered intermetallic compounds(IMC)provide unique electronic and geometrical effects as well as stronger intermetallic interactions due to the ordered arrangement of metal atoms,thus exhibiting superior electrocata-lytic activity and durability.However,quantitatively analyzing the ordering degree of IMC and exploring the correlation between the ordering degree and ORR activity remains extremely challenging.Herein,a series of ternary Pt_(2)NiCo interme-tallic catalysts(o-Pt_(2)NiCo)with different ordering degree were synthesized by annealing temperature modulation.Among them,the o-Pt_(2)NiCo which annealed at 800℃for two hours exhibits the highest ordering degree and the optimal ORR ac-tivity,which the mass activity of o-Pt_(2)NiCo is 1.8 times and 2.8 times higher than that of disordered Pt_(2)NiCo alloy and Pt/C.Furthermore,the o-Pt_(2)NiCo still maintains 70.8%mass activity after 30,000 potential cycles.Additionally,the ORR activity test results for Pt_(2)NiCo IMC with different ordering degree also provide a positive correlation between the ordering degree and ORR activity.This work provides a prospective design direction for ternary Pt-based electrocatalysts.
基金the National Key Research and Devel-opment Program of China(No.2022YFB3709000)the National Natural Science Foundation of China(Nos.52101019,52122408,52071023,52474397)+1 种基金support from the Fundamental Research Funds for the Central Universities(University of Science and Technology Beijing,No.FRF-TP-2021-04C1,and 06500135)supported by USTB MatCom of Beijing Advanced Innovation Center for Materials Genome Engineering.
文摘Martensitic transformation plays a pivotal role in strengthening and hardening of steels,yet an accu-rate interatomic potential for a comprehensive description of the martensitic phase formation in Fe-C alloys is lacking.Herein,we developed a deep learning-based interatomic potential to perform molecu-lar dynamics(MD)simulations to study the martensitic phase transformation across a range of carbon(C)concentrations.The results revealed that an increased C concentration leads to a suppressed phase boundary movement and a decelerated phase transformation rate.To overcome the timescale limitations inherent in MD simulations,metadynamics sampling was employed to accelerate the simulations of C dif-fusion.We found that C atoms tend to cluster at distances equivalent to the lattice parameter of Fe with the same sublattice occupation,leading to local lattice tetragonality.Such C-ordered structures effectively inhibit dislocation movement and enhance strength.The stress field induced by dislocations facilitates a higher degree of ordering,and the formation of C-ordered structures was identified as a potentially cru-cial strengthening mechanism for martensitic steels.The consistency between our simulation results and reported experimental observations underscores the effectiveness of the developed DP model in simu-lating martensitic phase transformation in Fe-C alloys,providing detailed insights into the mechanisms underlying this process.This work not only advances the understanding of martensitic phase transforma-tions in Fe-C alloys but also establishes a powerful computational framework for designing steels with optimized mechanical properties through the precise control of carbon ordering and dislocation behavior.
基金provided by the Nano and Material Technology Development Program(RS-2023-00281246)via the National Research Foundation of Korea,Ministry of Science and ICT,KoreaThe JEOL JSM-7001F,JEOL ARM 200F,and FEI Helios G3 CX FIB-SEM were funded by the Australian Research Council-Linkage,Infrastructure,Equipment and Facilities GrantsNos.LE0882613,LE120100104 andLE160100063,respectivelyThe Oxford Instruments 80 mm2 X-Max EDS detector and the JEOL JEM F200 were funded via the 2012 UOW Major Equipment Grant and 2019 UOW Equipment Replacement Grant schemes,respectively.
文摘Medium-entropy alloys(MEAs)have garnered significant interest due to their unique mechanical prop-erties,but phase instabilities such as the formation of brittle sigma(σ)phase during annealing pose challenges to their practical application.This study investigates the microstructural evolution and me-chanical behavior of an 80%cold-rolled Fe_(45)Co_(35)Cr_(10)V_(10)MEA that was isochronally annealed between 100℃ and 900℃ for 300 s and characterized using hardness indentations,in-situ X-ray diffraction,and thermodynamic calculations,with high-resolution electron microscopy detailing microstructural evo-lution at 625℃,675℃,and 725℃.The results show increases in Vickers hardness between 500℃ and 625℃,attributed to the nucleation of a Cr-and V-rich sigma(σ)phase,primarily at the bcc grain boundaries.Beyond 625℃,the hardness decreased due toσ-phase dissolution,recovery of bcc and fcc phases,bcc→fcc phase reversion,and recrystallization of the reverted fcc phase.Scanning-transmission electron microscopy and transmission Kikuchi diffraction revealed a Kurdjumov-Sachs orientation rela-tionship(OR)at 675℃ and a near Nishiyama-Wassermann OR at 725℃ for bcc-fcc interfaces,whereas bcc-σand fcc-σinterfaces showed no dominant OR.In addition toσphase,two types of bcc phase were identified at 625℃.Type 1 bcc initially retained a near-nominal composition and a disordered crystal structure from deformation-induced bcc martensite but gradually became Fe-enriched and Cr-and V-depleted up to 725℃.In contrast,Type 2 bcc phase was Fe-depleted and Co-enriched at 625℃ but dis-appeared at 675℃,coinciding with the onset of bcc→fcc phase reversion.This phase also exhibited B2-like chemical short-range ordering,with alternating FeCo-rich and CrV-rich domains.This study provides insights into the complex phase transformation occurring between 500℃ and 725℃ in a Fe_(45)Co_(35)Cr_(10)V_(10)MEA,which can be leveraged to design alloys with optimized mechanical properties for practical appli-cations.
基金financially supported by the State Administration for Market Regulation,China(No.2021MK050)the National Natural Science Foundation of China(Nos.50971043,51171046,21973012)+3 种基金the Key Research and Development Program of China(Nos.2022YFB3807200,CISRI-21T62450ZD)the Natural Science Foundation of Fujian Province,China(Nos.2021J01590,2020J01351,2018J01754,2020J01474)the Student Research and Training Program(SRTP) of Fuzhou University,China(No.29320)Fujian Provincial Department of Science & Technology,China(No.2021H6011)。
文摘In order to understand the influence of ordering behaviors on the thermodynamic and mechanical properties of multi-principal element alloys(MPEAs),the temperature-dependent thermodynamic properties and mechanical properties of FCC_CoNiV MPEAs were comparatively predicted,where the alloys were modeled as the ordered configurations based on our previously predicted site occupying fractions(SOFs),as well as disordered configuration based on traditional special quasi-random structure(SQS).The ordering behavior not only improves the thermodynamic stability of the structure,but also increases the elastic properties and Vickers hardness.For example,at 973 K,the predicted bulk modulus(B),shear modulus(G),Young’s modulus(E),and Vickers hardness(HV)of FCC_CoNiV MPEA based on SOFs configuration are 187.82,79.03,207.93,and 7.58 GPa,respectively,while the corresponded data are 172.58,57.45,155.14,and 4.64 GPa for the SQS configuration,respectively.The Vickers hardness predicted based on SOFs agrees considerably well with the available experimental data,while it is underestimated obviously based on SQS.
基金supported by the National Natural Science Foundation of China(Nos.22193042,22125110,22075285,52473283,21921001,U21A2069)the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(No.ZDBS-LY-SLH024)the Youth Innovation Promotion of Chinese Academy of Sciences(No.2020307)。
文摘Polar semiconductors,particularly the emerging polar two-dimensional(2D)halide perovskites,have motivated immense interest in diverse photoelectronic devices due to their distinguishing polarizationgenerated photoelectric effects.However,the constraints on the organic cation's choice are still subject to limitations of polar 2D halide perovskites due to the size of the inorganic pocket between adjacent corner-sharing octahedra.Herein,a mixed spacer cation ordering strategy is employed to assemble a polar 2D halide perovskite NMAMAPb Br_(4)(NMPB,NMA is N-methylbenzene ammonium,MA is methylammonium)with alternating cation in the interlayer space.Driven by the incorporation of a second MA cation,the perovskite layer transformed from a 2D Pb_(7)Br_(24)anionic network with corner-and face-sharing octahedra to a flat 2D PbBr_(4)perovskite networks only with corner-sharing octahedra.In the crystal structure of NMPB,the asymmetric hydrogen-bonding interactions between ordered mixed-spacer cations and 2D perovskite layers give rise to a second harmonic generation response and a large polarization of 1.3μC/cm^(2).More intriguingly,the ordered 2D perovskite networks endow NMPB with excellent self-powered polarization-sensitive detection performance,showing a considerable polarization-related dichroism ratio up to 1.87.The reconstruction of an inorganic framework within a crystal through mixed cation ordering offers a new synthetic tool for templating perovskite lattices with controlled properties,overcoming limitations of conventional cation choice.
基金supported by the National Key Research and Development Program of China(Nos.2020YFA0907300 and 2021YFB3501404)the National Natural Science Foundation of China(Nos.52301234,52371179,and 52071070)+1 种基金the Doctoral Start-up Foundation of Liaoning Province(No.2023-BS-059)the Fundamental Research Funds for the Central Universities(No.N2309002).
文摘L1_(0)-FePt nanoparticles(NPs)are urgently anticipated because of their promising applications.However,the preparation of the NPs with both of high ordering degree and super-fine size is still a challenge.Inspired by recent studies on the effect of vacancy defects on structural ordering,we proposed an intentional vacancy defect design strategy for directly synthesizing highly ordered FePt NPs.In the present work,we used the first-principle calculations to investigate the influence of doping typical elements(Cu,Ag,and Pb)on the vacancy formation energy(E_(vac))of FePt NPs.The vacancy defects were effectively formed by introducing elements of larger atomic radii and higher propensity for segregation into the FePt lattice,facilitating the diffusion of Fe and Pt atoms.The Pb doping showed remarkable efficacy in promoting the ordering transition.Experimentally,wet-chemical synthesis confirmed the success of the proposed strategy in achieving highly ordered L1_(0)-FePt NPs with exceptional magnetic properties and super-fine size(ordering degree of 0.896,impressive coercivity of 21.74 kOe,and small particle size of 9.02 nm).Additionally,we have deduced a diffusion model elucidating the formation process of the ordered FePt NPs,focusing on the migration of Pb atoms from the center to the surface of the particles.This migration is demonstrated to generate more vacancies and promote the transition to the ordered L1_(0)-FePt phase.The findings of this research offer valuable insights into synthesizing highly ordered and ultrafine L1_(0)-type nanomaterials.
基金supported by the National Natural Science Foundation of China(Grant No.52231001)Evan Ma and Jun Ding also acknowledge XJTU for hosting their research at the Center for Alloy Innovation and Design(CAID).
文摘1.Introduction Multi-principal element alloys(MPEAs),with compositions in the central region of the multicomponent phase diagram,have been dubbed"high-entropy alloys"(HEAs)in recent years[1-11].A more general term currently accepted by the community for these MPEAs is complex concentrated alloys or compositionally complex alloys(CCAs)[12].These alloys are usually based on single-phase multi-principal element solid solutions,with no need or possibility to distinguish which species constitutes the solvent and which ones are solutes.This Viewpoint and Perspective article focuses on a salient feature in the internal structure of MPEAs,different from traditional metals and solvent-(dilute)solute solutions.Specifically,the unusual trait to be highlighted for these heavily concentrated solutions is their inherent chemical inhomogeneity on the nanoscale,in terms of the high propensity for compositional fluctuation and local chemical order.
基金supported by the National Natural Science Foundation of China(Grant Nos.12204482 and U2430211)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2020L0537)the Fundamental Research Program of Shanxi Province(Grant No.202103021224250)the Hainan Provincial Natural Science Foundation of China(Grant No.225MS076).
文摘The ground-state magnetic ordering of uranium mononitride(UN)remains a contentious topic due to the unexpected lack of crystallographic distortion in the traditionally accepted 1k antiferromagnetic(AFM)state.This discrepancy casts doubt on the validity of the 1k magnetic ordering of UN.Here,we investigate the crystal structure,high-pressure phase transitions,and dynamical and mechanical properties of UN in its 1k and 3k AFM ground states using density functional theory(DFT).Our results reveal that the undistorted 3k AFM state of Fm3m within the DFT+U+SOC scheme is more consistent with experimental results.The Hubbard U and spin-orbit coupling(SOC)are critical for accurately capturing the crystal structure,high-pressure structural phase transition,and dynamical properties of UN.In addition,we have identified a new high-pressure magnetic phase transition from the nonmagnetic(NM)phase of R3m to the P63/mmc AFM state.Electronic structure analysis reveals that the magnetic ordering in the ground state is primarily linked to variations in partial 5f orbital distributions.Our calculations provide valuable theoretical insights into the complex magnetic structures of a typical strongly correlated uranium-based compound.Moreover,they provide a framework for understanding other similar actinide systems.
基金supported by the National Natural Science Foundation of China(52202266 and 52403379).
文摘Full-manganese(Mn)Li-rich materials have gained attention owing to the limited availability of cobalt-or nickel-based cathodes commonly used in batteries,which greatly restricts their potential for large-scale application.However,their practical implementation is hindered by the rapid voltage/capacity decay during cycling and the long-standing problem of redox kinetics due to their poor ionic conductivity based on the ordered honeycomb structure.In this study,the kinetic and thermodynamic properties of intralayer disordered and ordered Li-rich full-Mn-based cathode materials were compared,demonstrating that the disordered R3m Li_(0.6)[Li_(0.2)Mn_(0.8)]O_(2)(D-LMO)delivers a significant advantage of rate capability over the ordered C2/m Li_(0.6)[Li_(0.2)Mn_(0.8)]O_(2)(O-LMO).Meanwhile,the D-LMO keeps superior capacity retention of up to 99%after 50 cycles under 25 mAg^(-1).In comparsion,the capacity retention of the O-LMO drops to just 70%,and its average discharge voltage is 0.2 V lower than that of the D-LMO.Herein,we conducted systematic density functional theory(DFT)simulations,focusing on the electronic structure modulation governing the voltage platform between the ordered and disordered phases.The ab initio molecular dynamics(AIMD)results indicated that the energy of the intralayer disordered structure fluctuates around the equilibrium position without any abrupt drops,demonstrating excellent stability.This study enhances the understanding of intralayer disordered full-Mn Li-rich material and provides insights into the design of low-cost,high-performance cathode materials for Li-ion batteries.
基金Project supported by the Natural Science Foundation of Shandong Province of China (Grant No Y2008A23)the Natural Science Foundation of Liaocheng University (Grant No X071049)
文摘In this paper by virtue of the technique of integration within an ordered product （IWOP） of operators and the intermediate coordinate-momentum representation in quantum optics, we derive the normal ordering and antinormal ordering products of the operator （fQ＋gP）n when n is an arbitrary integer. These products are very useful in calculating their matrix elements and expectation values and obtaining some useful mathematical formulae. Finally, the applications of some new identities are given.
基金supported by the National Natural Science Foundation of China(No.10274075)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20030358056).
文摘The ultrasonic, magnetic and transport properties of Nd0.5Ca0.5Mn1-xAlxO3 （x=0, 0.03） were studied from 15 to 300 K. The temperature dependencies of resistivity and magnetization show that Nd0.5Ca0.5MnO3 undergoes a charge ordering transition at TCO-257 K. An obvious softening of the longitudinal sound velocity above TCO and a dramatic stiffening below Too accompanied by an attenuation peak were observed. These features imply a strong electron phonom interaction via the Jahn-Teller effect iu the sample, Another broad attenuation peak was observed at around Tp-80 K. This anomaly is attributed to the phase separtion between the antiferromagnetic （AFM） and paramagnetic （PM） phases and gives a direct evidence for spin-phonon coupling in the compound. For the x=0.03 sample, both the minimum of sound velocity and attenuation peaks shift to a lower temperature. The results indicate that the charge ordering and CE-type AFM state in Nd0.5Ca0.5MnO3 are both partially suppressed by replacing Mn with A1.
文摘A series of TiAl+Nb alloys with various Nb contents has been employed to explore phase relationship and the evolution of microstructure.A new ordered γ derivative (γ1) has been observed in the alloy containing 20 at% Nb.The additional diffraction spots added to the diffraction pattern of L10 (TiAl) structure have been found in the alloy containing Nb up to 11 at% in terms of further ordering.The transformation from L10 (TiAl) structure to the further ordering phase,γ1,is a continuous ordering process with the substitution of Nb atoms for Ti atoms in alloys with over-stoichiometric Al content of TiAl.The possible transformtion characterzation has been discussed.
基金Project supported by the National Key Basic Research Program of China(Grant No.2019YFA0308500)the National Natural Science Foundation of China(Grant No.11721404)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB33030200).
文摘The first-principles calculations were used to explore the tunable electronic structure in DyNiO_(3)(DNO)under the effects of the biaxial compressive and tensile strains.We explored how the biaxial strain tunes the orbital hybridization and influences the charge and orbital ordering states.We found that breathing mode and Jahn–Teller distortion play a primary role in charge ordering state and orbital ordering state,respectively.Additionally,the calculated results revealed that the biaxial strain has the ability to manipulate the phase competition between the two states.A phase transition point has been found under tensile train.If the biaxial train is larger than the point,the system favors orbital ordering state.If the strain is smaller than the point,the system is in charge ordering state favorably.
文摘This paper establishes an ordering contraction mapping principle for increasing mapping in partial ordering metric spaces, and applies it to prove the existence and uniqueness of fixed point for some nonlinear operators controlled by a linear operator and phi-concave operator in a partial ordering Banach space. Therefore, this two results are unified.
基金Project(51071181)supported by the National Natural Science Foundation of ChinaProject(2013FJ4043)supported by the Natural Science Foundation of Hunan Province,China
文摘Taking experimental path on disordering AuCuI（AAuCu8A4）composed of A Au8 and ACu4 stem alloy genes as an example, three discoveries and a method were presented. The ability of Au Cu I（AAu Cu8 A4）to keep structure stabilization against changing temperature is attributed to the fact that the AAu8 and ACu4 potential well depths greatly surpass their vibration energies, which leads to the subequilibrium of experimental path. A new atom movement mechanism of AuCuI（AAuACu84）to change structure for suiting variation in temperature is the resonance activating-synchro alternating of alloy genes, which leads to heterogeneous and successive subequilibrium transitions. There exists jumping order degree, which leads to the existence of jumping Tj-temperature and an unexpected so-called ＂retro-effect＂ about jumping temperature retrograde shift to lower temperatures upon the increasing heating rate. A set of subequilibrium holographic network path charts were obtained by the experimental mixed enthalpy path method.
基金co-supported by the General Armament Department Pre-research Foundation of China (Nos. 51304010206, 51327 020105)
文摘Rational planning of spares configuration project is an effective approach to improve equipment availability as well as reduce life cycle cost （LCC）. With an analysis of various impacts on support system, the spares demand rate forecast model is constructed. According to systemic analysis method, spares support effectiveness evaluation indicators system is built, and then, initial spares configuration and optimization method is researched. To the issue of discarding and con-sumption for incomplete repairable items, its expected backorders function is approximated by Laplace demand distribution. Combining the （s-1, s） and （R, Q） inventory policy, the spares resup-ply model is established under the batch ordering policy based on inventory state, and the optimi-zation analysis flow for spares configuration is proposed. Through application on shipborne equipment spares configuration, the given scenarios are analyzed under two constraint targets：one is the support effectiveness, and the other is the spares cost. Analysis reveals that the result is consistent with practical regulation;therefore, the model＇s correctness, method＇s validity as well as optimization project＇s rationality are proved to a certain extent.
基金supported by the National Natural Science Foundation of China(Nos.51921001,51871016,51971017,51531001,51901013,and 51671021)111 Project(B07003)+3 种基金Program for Changjiang Scholars and Innovative Research Team in University of China(IRT-14R05)the Projects of SKLAMM-USTBthe financial support from the Fundamental Research Fund for the Central Universities(No.FRF-BD-19002B)National Key Basic Research Program,China(No.2016YFB0300502)。
文摘In this letter,we briefly summarize experimental and theoretical findings of fo rmation and characterization of short-range orderings(SROs)as well as their effects on the defo rmation behavior of high-entropy alloys(HEAs).We show that existence of SROs is a common yet key structural feature of HEAs,and tuning the degree of SROs is an effective way for optimizing mechanical properties of HEAs.In additional,the challenges concerning about formation mechanism and characterization of SROs in HEAs are discussed,and future research activities in this regard are also proposed.
基金supported by the Key Program of the National Natural Science Foundation of China (No.19934003)the Key Program of Natural Science Research of Anhui Education Department (No.KJ2011A259+3 种基金 KJ2008A34ZC)the Natural Science Research Programs of Anhui Education Department, China (No.KJ2010B229No.KJ2010B228No.KJ2009B281Z)
文摘Polycrystalline samples of La0.4Cao.6Mn1-xCrxO3 （x = 0.00, 0.02, 0.04, 0.06） were prepared by the solid state reaction method. The influence of Cr3＋ substitution for Mn3＋ on the magnetic property and charge ordering phase of La0.4Ca0.6MnO3 was studied through the measurements of X-ray diffraction （XRD）, magnetization-temperature （M-T） curves and electron spin resonance （ESR） spectra. The experimental results indicate that the mother＇s body of La0.4Ca0.6MnO3 has very complicated magnetic structure, exhibits charge ordering phase at 258 K, and shows long-range strongly correlated charge ordering-antiferromagnetism （CO-AFM） phase from 175 to 50 K. Spin glass state appears when the temperature decreases to about 41 K. When the Cr substitution amount is x = 0.06, the charge ordering phase of the mother＇s body is de-stroyed, because the Cr3＋ substitution for Mn3＋ destroys the spin order of CE-type antiferromagnetism, and thus leads to the melting of charge ordering. It is verified experimentally that the strong coupling between charge order and spin order exists in the charge order system of CE-type antiferromagnetism.
基金financially supported by the National Natural Science Foundation of China(Nos.52101019,52071023,51901013,52122408)the financial support from the Fundamental Research Funds for theCentral Universities(University of Science and Technology Beijing,Nos.FRF-TP-2021-04C1,06500135)supported by USTB MatCom of Beijing Advanced Innovation Center for Materials Genome Engineering。
文摘Nanograined(NG)materials often suffer from low thermal stability owing to the high volume fraction of grain boundaries(GBs).Herein,we investigate the possibility of utilizing local chemical ordering(LCO)for improving the thermal stability of NG FeCoNiCrMn highentropy alloys(HE As).NG HE As with two different grain sizes were considered.Tensile tests and creep test simulations were then performed to reveal the influence of LCO on the mechanical properties and thermal stability of NG HE As.After performing hybrid molecular dynamics and Monte Carlo simulations,Cr atoms were found to accumulate at GBs.By analyzing the atomic structure evolution during the deformation process,we found that the formation of LCO effectively stabilized the GBs and inhibited GB movement.In addition,dislocation nucleation from GBs and dislocation movement was also hindered.The inhibiting effect of LCO on GB movement and dislocation activity is more prominent than in the NG model with smaller grain sizes.The current simulation results suggest a possible strategy for enhancing the thermal stability of NG HEAs for service in a high-temperature environment.
