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
Two pairs of novel 6/6/6/9 tetracyclic merosesquiterpenoid enantiomers,dauroxonanols A(1)and B(2),possessing an unprecedented 9,15-dioxatetracyclo[8.5.3.0^(4.17).0^(14.18)]octadecane core skeleton,were isolated from R...Two pairs of novel 6/6/6/9 tetracyclic merosesquiterpenoid enantiomers,dauroxonanols A(1)and B(2),possessing an unprecedented 9,15-dioxatetracyclo[8.5.3.0^(4.17).0^(14.18)]octadecane core skeleton,were isolated from Rhododendron dauricum.The nuclear magnetic resonance(NMR)spectra of 1 and 2 showed very broad resonances,and^(13)C NMR spectrum of 1 exhibited only 13 instead of 22 carbon resonances.These broadening or missing NMR resonances led to a great challenge to elucidate their structures using NMR data analysis.Their structures and absolute configurations of 1 and 2 were finally determined by single crystal X-ray diffraction analysis,chiral separation,and electronic circular dichroism(ECD)calculations.Plausible biosynthetic pathways for 1 and 2 are proposed.Conformational analysis,density functional theory(DFT)calculations,and dynamic NMR assigned the coalescent NMR phenomena of 1 and 2 to the conformational changes of the flexible oxonane ring.Dauroxonanols A(1)and B(2)showed potentα-glucosidase inhibitory activities,2-8 times potent than acarbose,an antidiabetic drug targetingα-glucosidase in clinic.展开更多
Magnets exhibiting the Kitaev interaction,a bond-dependent magnetic interaction in honeycomb lattices,are generally regarded as promising candidates for hosting novel phenomena like quantum spin liquid states.However,...Magnets exhibiting the Kitaev interaction,a bond-dependent magnetic interaction in honeycomb lattices,are generally regarded as promising candidates for hosting novel phenomena like quantum spin liquid states.However,realizing such magnets remains a significant challenge.Recently,some studies have suggested honeycomb magnets A_(3)Ni_(2)XO_(6)(A=Li,Na;X=Bi,Sb)with a high spin S=1 could serve as potential candidates for realizing strong Kitaev interactions.In this work,we systematically investigate their magnetic properties,with a particular emphasis on their Kitaev interactions,using first-principles calculations and Monte Carlo simulations.Our results indicate that all A_(3)Ni_(2)XO_(6)compounds are zigzag antiferromagnets,and their magnetic moments almost tend to be out of plane.We find that their dominant magnetic interactions are the nearest-neighbor ferromagnetic and third-nearest-neighbor antiferromagnetic Heisenberg interactions,while their Kitaev interactions are extremely weak.By analyzing their electronic structures and the mechanism of generating their magnetic interactions,we reveal that either artificially tuning spin-orbit coupling or applying strain cannot produce sufficient spin-orbit entangled states to realize the intriguing Kitaev interactions.Our work advances the understanding of the magnetism in A_(3)Ni_(2)XO_(6)compounds and provides insights for further exploration of Kitaev physics in honeycomb magnets.展开更多
This study investigates the application of Gurney and flight of fragment equations,typically used to predict metal fragment velocities,in modeling the water jet behavior.Three shotgun cartridge sizes were used as the ...This study investigates the application of Gurney and flight of fragment equations,typically used to predict metal fragment velocities,in modeling the water jet behavior.Three shotgun cartridge sizes were used as the energy source:2.59 g,5.83 g,and 7.13 g.Two configurations were tested:standard(full-barrel water load)and"negative 8"(partial water load).High-speed footage captured water column velocities,and Gurney models,including infinitely tamped and open-faced configurations,combined with the flight of fragment model were used to assess prediction accuracy.Results showed charge strength significantly affects water column velocity,with higher strengths yielding greater stability and velocity retention over distance.The infinitely tamped Gurney model closely predicted experimental velocities,deviating by as little as 1.4%for standard charges and 2.8% for negative 8 charges.Additionally,interesting dynamics such as a 1-2°rise in jet height and the rear overtaking the front was observed.These findings have significant implications for optimizing PAN disruptors and enhancing performance in high-velocity fluid applications and explosive breaching systems.展开更多
Neutron-rich boron,carbon,and nitrogen isotopes have garnered extensive experimental and theoretical interest.In the present work,we conducted a comprehensive study of these nuclei by utilizing ab initio valence-space...Neutron-rich boron,carbon,and nitrogen isotopes have garnered extensive experimental and theoretical interest.In the present work,we conducted a comprehensive study of these nuclei by utilizing ab initio valence-space in-medium similarity renormalization group calculations with chiral nucleon-nucleon and three-nucleon interactions.First,we systematically calculated the spectra of nuclei.Our results align well with the available experimental data,which are comparable to phenomenological shell model calculations.Subsequently,the evolution of the N=14 and N=16 shell gaps is discussed based on the calculated spectra and the effective single-particle energies.Our calculations suggest that the N=14 neutron subshell is present in the oxygen isotopes but disappears in the boron,carbon,and nitrogen isotopic chains.Moreover,the N=16 subshell is present in all isotopes but gradually decreases from^(24)O to^(21)B.These results provide valuable information for future studies.展开更多
High multipole electromagnetic transitions are rare in nature.The highest-multipole transition observed in atomic nuclei is the electric hexacontatetrapole E6 transition from the T_(1/2)=2.54(2)-min J^(π)=1_(9/2)-iso...High multipole electromagnetic transitions are rare in nature.The highest-multipole transition observed in atomic nuclei is the electric hexacontatetrapole E6 transition from the T_(1/2)=2.54(2)-min J^(π)=1_(9/2)-isomer to the 7/2^(-)ground state in^(53)Fe with an angular momentum change of six units.In the present work,we performed ab initio calculations for this unique case by employing chiral effective field theory(EFT)forces.The in-medium similarity renormalization group is used to derive the valence-space effective Hamiltonian and multipolar transition operators.Bare nucleon charges were used in all the multipolar transition rate calculations,providing good agreement with the experimental data.The valence space takes the full fp shell.In^(53)Fe,the low-lying states were dominated by the 0f_(7/2)component.Two different versions of the chiral EFT two-plus three-nucleon interaction were used to test the dependence on the interaction used.We also tested the convergence of the transition rate calculations against the harmonic oscillator parameter hΩand basis truncations e_(max)and E_(3max)for twoand three-nucleon forces,respectively.展开更多
Currently,the development of high-efficiency two-dimensional(2D)transistors is still hindered by the limited availability of suitable semiconductors and the contact resistance between the metal contact and the 2D semi...Currently,the development of high-efficiency two-dimensional(2D)transistors is still hindered by the limited availability of suitable semiconductors and the contact resistance between the metal contact and the 2D semiconductors.Endeavors to address these challenges are highly desired.In this study,we conducted a comprehensive exploration of the potential 2D transition metal dinitrides(TMN_(2)s,TM=all the 3d,4d and 5d transition metals)with hexagonal(h-)and trigonal(t-)phases through systematic first-principles calculations.Among all h-TMN_(2)s and t-TMN_(2)s structures,we identified 8 TMN_(2)s that exhibit dynamical and thermal stability at room temperature.Of these,the h-TiN_(2),h-ZrN_(2)and h-HfN_(2)arefound to be semiconductors,and their direct bang gap,calculated at the HSE06 level,are 1.48,1.96 and 2.64 eV,respectively.The electron and hole mobility(μ_(e)andμ_(h))of these three structures exceed 1×10^(4)and1×10^(3)cm^(2)·V^(-1)·s^(-1),respectively.Especially,theμeof h-TiN_(2)amounts to 2.5×10^(4)cm^(2)·V^(-1)·s^(-1),and theμhof h-ZrN_(2)reaches to 7.7×10^(3)cm^(2)·V^(-1)·s^(-1).Importantly,unlike the MoS_(2)system,h-TMN_(2)forms Ohm contacts with both transition metals(e.g.,Cu)and 2D metals(e.g.,graphene),with tunneling possibilities exceeding 50%in the Cu system.These outstanding intrinsic semiconductor properties and contact characteristics exhibited by h-TMN_(2)highlight the immense potential of transition metal dinitrides in driving the advancement of next-generation information devices.Our findings significantly broaden the range of 2D materials and provide valuable insights for the development of high-eficiency 2D information devices.展开更多
Control of hyperfine interaction strength of shallow donors in Si is one of the central issues in realizing Kane quantum computers.First-principles calculations on the hyperfine Stark shift of shallow donors are chall...Control of hyperfine interaction strength of shallow donors in Si is one of the central issues in realizing Kane quantum computers.First-principles calculations on the hyperfine Stark shift of shallow donors are challenging since large supercells are needed to accommodate the delocalized donor wave functions.In this work,we investigated the hyperfine Stark shift and its strain tunability for shallow donors P and As in Si using the potential patching method based on first-principles density functional theory calculations.The good agreement between our calculations and experimental results confirms that the potential patching method is a feasible and accurate first-principles approach for studying wave-function-related properties of shallow impurities,such as the Stark shift parameter.It is further shown that the application of strain expands the range of hyperfine Stark shift and helps improve the response of shallow donor based qubit gates.The results could be useful for developing quantum computing architectures based on shallow donors in Si.展开更多
Ag/Al_(2)O_(3) powders are highly effective catalytic materials utilized in the epoxidation of ethylene to produce ethylene oxide.One of the critical challenges in this catalytic process is the stability of nano-sized...Ag/Al_(2)O_(3) powders are highly effective catalytic materials utilized in the epoxidation of ethylene to produce ethylene oxide.One of the critical challenges in this catalytic process is the stability of nano-sized Ag particles,especially during high-temperature catalysis.However,this issue can be effectively addressed through in-situ reaction synthesis.To gain a deeper understanding of the underlying mechanisms,the phase transformation process and the thermodynamic mechanism of the oxidation reaction in the Ag/Al_(2)O_(3) system have been investigated using firstprinciples thermodynamic calculations in conjunction with traditional thermodynamic data.These calculations,whose accuracy has been verified,provide valuable insights into the behavior of Ag and Al under different conditions.The results indicate that,during AgAl solid-solution oxidation,Ag-containing Al preferentially forms the stable intermediate phase Ag2Al instead of undergoing direct oxidation;this pathway becomes thermodynamically more favorable at higher Ag concentrations.With increasing temperature,Ag2Al is further oxidized to yield Ag and Al_(2)O_(3).It is also found that above 237℃,Ag2O and AgAlO2 become unstable.The overall reaction pathway is solid solution→Ag2Al→Ag+Al_(2)O_(3).This comprehensive study provides a robust theoretical calculation basis for the development and optimization of in-situ reaction-synthesized Ag/Al_(2)O_(3) powder composite materials,which have significant potential for practical applications in catalysis.展开更多
Understanding the adsorption behavior of heavy metals and metalloids on clay minerals is essential for remediating heavy metal-contaminated soils.The adsorption of heavy metals and metalloids on illite(001)and sodium ...Understanding the adsorption behavior of heavy metals and metalloids on clay minerals is essential for remediating heavy metal-contaminated soils.The adsorption of heavy metals and metalloids on illite(001)and sodium montmorillonite(Na-MMT)(001)surfaces was investigated using first-principles calculations in this study,especially As atom and H_(3)AsO_(3) molecule.The adsorption energies of the As atom were−1.94 eV on the illite(001)and−0.56 eV on the Na-MMT(001),whereas,the adsorption energies of the H_(3)AsO_(3) molecule were−1.40 eV on illite(001)and−1.01 eV on Na-MMT(001).The above results indicate that the adsorption was more energetically favorable on illite(001).Additionally,compared to Na-MMT(001),there were more significant interactions between the atoms/molecules on the illite(001).After As atom and H_(3)AsO_(3) molecule adsorption,the electrons were transferred from mineral surface atoms to the adsorbates on both illite(001)and Na-MMT(001)surfaces.Moreover,the adsorption of As atom on illite(001)and Na-MMT(001)surfaces were more energy favorable compared to Hg,Cd,and Cr atoms.Overall,this work provides new insights into the adsorption behavior of As atoms and As molecules on illite and Na-MMT.The results indicate that illite rich soils are more prone to contamination by arsenic compared to soils primarily composed of Na-MMT minerals.展开更多
To explain the influence mechanism of MgO on the consolidation and reduction characteristics of roasted iron pellets,the properties and structure of pellets were investigated from multi-dimensions.It indicated that th...To explain the influence mechanism of MgO on the consolidation and reduction characteristics of roasted iron pellets,the properties and structure of pellets were investigated from multi-dimensions.It indicated that the MgO addition decreased the reduction swelling index(RSI)and reduction degree of pellets in both CO and H_(2)atmospheres.During the stepwise reduction process of Fe2O3→Fe3O4→FeO,the reduction behaviour of pellets in CO and H_(2)was similar,while the reduction rate of pellets in H_(2)atmosphere was almost twice as high as that in CO atmosphere.During the stepwise reduction process of FeO→Fe,the RSI of pellets showed a logarithmic increase in CO atmosphere and a linear decrease in H_(2)atmosphere.As investigated by first-principles calculations,C and Fe mainly formed chemical bonds,and the CO reduction process released energy,promoting the formation of iron whiskers.However,H and Fe produced weak physical adsorption,and the H_(2)reduction process was endothermic,inhibiting the generation of iron whiskers.With Mg2+doping in FexO,the nucleation region of iron whiskers expanded in CO reduction process,and the morphology of iron whiskers transformed from“slender”to“stocky,”reducing RSI of the pellets.展开更多
We have investigated the phase stability,magnetic properties,and martensitic transformation thermodynamics/kinetics of the Ni_(24-x)Mn_(18+x+y)Sn_(6-y)(x,y=0,1,2)system by combining the first-principles calculations a...We have investigated the phase stability,magnetic properties,and martensitic transformation thermodynamics/kinetics of the Ni_(24-x)Mn_(18+x+y)Sn_(6-y)(x,y=0,1,2)system by combining the first-principles calculations and experiments.The calculation results show that the optimized lattice parameters are consistent with the experimental data.Respectively,we obtain the relation equation for the austenite formation energy(E_(form-A))and Mn content(X_(Mn)):E_(form-A)=507.358X_(Mn)-274.126,as well as for the six-layer modulated(6M)martensite formation energy(E_(form-6M))and Ni content(X_(Ni)):E_(form-6M)=-728.484X_(Ni)+264.374.The ternary phase diagram of the total magnetic moment was established.The excess Mn will reduce the total magnetic moment of 6M(Mag6M)and non-modulated(NM)(MagNM)martensites,with the following equations relating the total magnetic moment and Mn content:Mag_(6M)=-15.905X_(Mn)+7.902and Mag_(NM)=-14.781X_(Mn)+7.411,while the effect on austenite is complex.The variation of total magnetic moment is mainly dominated by the Mn atomic magnetic moment.The 3d electrons of Mn_(Sn)(Mn at Sn sublattice)play an important role in magnetic properties from the perspective of the electronic density of states.Based on the thermodynamics of martensitic transformation,the alloys will likely undergo austenite?6M?NM transformation sequence.Combining the thermodynamic and kinetic results,the martensitic transformation temperature decreases with x increasing and increases with y increasing.These results are expected to provide reference for predicting the phase stability and magnetic properties of NiMn-Sn alloys.展开更多
In the present work,a new Mg-Bi based alloy is developed by the addition of Zn and Ca in equiva-lent atom fraction with Bi.Mg-Bi and Mg-Bi-Zn-Ca alloys were prepared by extrusion at a ram speed of 20 mm/s.Room tempera...In the present work,a new Mg-Bi based alloy is developed by the addition of Zn and Ca in equiva-lent atom fraction with Bi.Mg-Bi and Mg-Bi-Zn-Ca alloys were prepared by extrusion at a ram speed of 20 mm/s.Room temperature mechanical properties and creep behaviors at 423 K were investigated.The results show that Zn and Ca co-addition shows little influence on average grain size and texture in-tensity but changes the dispersive Mg_(3)Bi_(2)into Mg_(2)Bi_(2)Ca particles in different sizes and a lower density.Twinning is largely activated during room-temperature deformation.Consequently,a slightly decreased proof strength but tripled elongation is shown at room temperature.Unexpectedly,large enhancement in creep resistance is detected after the co-alloying of Zn and Ca and the minimum creep rate is reduced by 10 to 20 times in the BZX621 alloy.Stress exponent n=4-5 indicates that the creep is a dislocation-climb controlled type.Post-mortem characterization on microstructure shows slip of dislocationc+aare also largely found in B6 as well as BZX621 alloy and cross-slip is detected more severe in B6 alloy.Dynamic segregation and precipitation are also seen in both alloys.Bi-clusters are seen dispersive across the grains in B6 and so did the PFZs that could undermine creep resistance at the grain boundaries.By contrast,Zn-rich needle-like precipitates are developed at most“ends”ofc+adislocations,which would hinder the further dislocation motions and thus improve the creep resistance.First-principles cal-culations were adopted and the results show that the thermal stability and thermomechanical properties of Mg_(2)Bi_(2)Ca are much better than that of Mg_(3)Bi_(2).Stacking faults energy is lowered down with the co-addition of Ca and Zn,which could inhibit the rate of dislocation climb and cross-slip.As a result,the im-proved creep resistance is obtained in the Mg-Bi-Zn-Ca alloys.Microstructural and controlling mechanism changes by thermal activation result in the unexpected enhancement in creep resistance with decreased room-temperature proof strength after co-addition.These findings could contribute to the development and optimization of creep-resistant Mg alloys in the future.展开更多
Reducing the exploration of multi-principal element alloy space is a key challenge to design high-performance U-based high-entropy alloy(UHEA).Here,the best combination of multi-principal element can be efficiently ac...Reducing the exploration of multi-principal element alloy space is a key challenge to design high-performance U-based high-entropy alloy(UHEA).Here,the best combination of multi-principal element can be efficiently acquired because proposed alloying strategy and screening criteria can substantially reduce the space of alloy and thus accelerate alloy design,rather than enormous random combinations through a trial-and-error approach.To choose the best seed alloy and suitable dopants,the screening criteria include small anisotropy,high specific modulus,high dynamical stability,and high ductility.We therefore find a shortcut to design UHEA from typical binary(UTi and UNb)to ternary(UTiNb),qua-ternary(UTiNbTa),and quinary(UTiNbTaFe).Finally,we find a best bcc senary UHEA(UTiNbTaFeMo),which has highest hardness and yield strength,while maintains good ductility among all the candidates.Compared to overestimation from empirical strength-hardness relationship,improved strength prediction can be achieved using a parameter-free theory considering volume mismatch and temperature effect on yield strength.This finding indicates that larger volume mismatch corresponds to higher yield strength,agreeing with the available measurements.Moreover,the dynamical stability and mechanical properties of candidates are greatly enhanced with increasing the number of multi-principal element,indicating the feasibility and effectiveness of adopted alloying strategy.The increasing of multi-principal element cor-responds to the increasing valence electron concentration(VEC).Alternatively,the mechanical properties significantly improve as increasing VEC,agreeing with measurements for other various bcc HEAs.This work can speed up research and development of advanced UHEA by greatly reducing the space of alloy composition.展开更多
Magnesium alloys have large reserves and good strength,attracting a lot of attention.Herein,the thermodynamic,elastic constants,and electronic properties of the Mg-Y-Zn ternary compounds were calculated;among them,MgY...Magnesium alloys have large reserves and good strength,attracting a lot of attention.Herein,the thermodynamic,elastic constants,and electronic properties of the Mg-Y-Zn ternary compounds were calculated;among them,MgYZn_(2) belongs to the cubic structure,MgYZn,Mg_(3)Y_(2)Zn_(4),and Mg_(14)YZn-1 belong to the hexagonal structure,Mg_(6)YZn-1,Mg_(6)YZn-2,MgY_(2)Zn,and Mg_(14)YZn-2 possess the orthorhombic structure,and Mg_(3)Y_(2)Zn_(3) is trigonal structure.The calculated cohesive energies of the results show that all compounds are thermodynamically stable.Moreover,the MgYZn_(2) compound exhibits the highest modulus of 76.84 MPa,and the Mg_(3)Y_(2)Zn_(3) has the biggest hardness of 6.6 GPa.In addition,the Mg_(6)YZn-2 has the strongest elastic anisotropic with A^(U) of 6.14 and A_(G) of 0.38,respectively.According to the population analysis,the Mg-Y covalent bond is due to the biggest bond population.The shortest weighted average bond length indicates that MgYZn_(2) has better elastic properties.Furthermore,the calculated limiting thermal conductivity results show that Mg_(14)YZn-2 has better thermal conductivity with maximum values of 0.94 W·m^(−1)·K^(−1) and 0.74 W·m^(−1)·K^(−1) for Clarke’s and Cahill’s models.展开更多
Rechargeable aluminum batteries with multi-electron reaction have a high theoretical capacity for next generation of energy storage devices. However, the diffusion mechanism and intrinsic property of Al insertion into...Rechargeable aluminum batteries with multi-electron reaction have a high theoretical capacity for next generation of energy storage devices. However, the diffusion mechanism and intrinsic property of Al insertion into MnO_(2) are not clear. Hence, based on the first-principles calculations, key influencing factors of slow Al-ions diffusion are narrow pathways, unstable Al-O bonds and Mn^(3+) type polaron have been identified by investigating four types of δ-MnO_(2)(O3, O'3, P2 and T1). Although Al insert into δ-MnO_(2) leads to a decrease in the spacing of the Mn-Mn layer, P2 type MnO_(2) keeps the long(spacious pathways)and stable(2.007–2.030 A) Al-O bonds resulting in the lower energy barrier of Al diffusion of 0.56 e V. By eliminated the influence of Mn^(3+)(low concentration of Al insertion), the energy barrier of Al migration achieves 0.19 e V in P2 type, confirming the obviously effect of Mn^(3+) polaron. On the contrary, although the T1 type MnO_(2) has the sluggish of Al-ions diffusion, the larger interlayer spacing of Mn-Mn layer,causing by H_(2)O could assist Al-ions diffusion. Furthermore, it is worth to notice that the multilayer δ-MnO_(2) achieves multi-electron reaction of 3|e|. Considering the requirement of high energy density, the average voltage of P2(1.76 V) is not an obstacle for application as cathode in RABs. These discover suggest that layered MnO_(2) should keep more P2-type structure in the synthesis of materials and increase the interlayer spacing of Mn-Mn layer for providing technical support of RABs in large-scale energy storage.展开更多
This comprehensive review examines the structural,mechanical,electronic,and thermodynamic properties of Mg-Li-Al alloys,focusing on their corrosion resistance and mechanical performance enhancement.Utilizing first-pri...This comprehensive review examines the structural,mechanical,electronic,and thermodynamic properties of Mg-Li-Al alloys,focusing on their corrosion resistance and mechanical performance enhancement.Utilizing first-principles calculations based on Density Functional Theory(DFT)and the quasi-harmonic approximation(QHA),the combined properties of the Mg-Li-Al phase are explored,revealing superior incompressibility,shear resistance,and stiffness compared to individual elements.The review highlights the brittleness of the alloy,supported by B/G ratios,Cauchy pressures,and Poisson’s ratios.Electronic structure analysis shows metallic behavior with varied covalent bonding characteristics,while Mulliken population analysis emphasizes significant electron transfer within the alloy.This paper also studied thermodynamic properties,including Debye temperature,heat capacity,enthalpy,free energy,and entropy,which are precisely examined,highlighting the Mg-Li-Al phase sensitive to thermal conductivity and thermal performance potential.Phonon density of states(PHDOS)confirms dynamic stability,while anisotropic sound velocities reveal elastic anisotropies.This comprehensive review not only consolidates the current understanding of the Mg-Li-Al alloy’s properties but also proposes innovative strategies for enhancing corrosion resistance.Among these strategies is the introduction of a corrosion barrier akin to the Mg-Li-Al network,which holds promise for advancing both the applications and performance of these alloys.This review serves as a crucial foundation for future research aimed at optimizing alloy design and processing methods.展开更多
I had the privilege and the pleasure to work closely with Stephen J. Pennycook for about twenty years, having a group of post-docs and Vanderbilt-University graduate students embedded in his electron microscopy group ...I had the privilege and the pleasure to work closely with Stephen J. Pennycook for about twenty years, having a group of post-docs and Vanderbilt-University graduate students embedded in his electron microscopy group at Oak Ridge National Laboratory, spending on average a day per week there. We combined atomic-resolution imaging of materials,electron-energy-loss spectroscopy, and density-functional-theory calculations to explore and elucidate diverse materials phenomena, often resolving long-standing issues. This paper is a personal perspective of that journey, highlighting a few examples to illustrate the power of combining theory and microscopy and closing with an assessment of future prospects.展开更多
Fire retardant CNTs/WPP/Gel composite papers were fabricated by incorporating bio-based carbon nanotubes(CNTs)recycled from mature beech pinewood sawdust(MB)and cellulosic waste printed paper(WPP)into a gelatin soluti...Fire retardant CNTs/WPP/Gel composite papers were fabricated by incorporating bio-based carbon nanotubes(CNTs)recycled from mature beech pinewood sawdust(MB)and cellulosic waste printed paper(WPP)into a gelatin solution(Gel)and allowing the mixture to dry at room temperature.The CNTs within the WPP matrix formed a network,enhancing the mechanical and thermal properties of the resulting CNTs paper sheet.In comparison to pure WPP/Gel,CNTs/WPP/Gel exhibited superior flexibility,mechanical toughness,and notable flame retardancy characteristics.This study provides a unique and practical method for producing flame-retardant CNTs/WPP/Gel sheets,suitable for diverse industrial applications,especially packaging,where used paper materials pose a significant fire risk.Bio-CNT-based fire-resistant packaging offers enhanced safety during transportation and storage.The sheets demonstrated increased strength and stiffness,with optimal mechanical properties achieved at a 20%CNTs loading.Additionally,thermal stability was improved,as confirmed by thermogravimetric analysis(TGA)and differential thermogravimetry(DTG).Flame retardancy tests revealed a rise in LOI(Limiting Oxygen Index)values with increasing CNTs content,indicating the CNTs’effectiveness in inhibiting combustion.The compatibility of recycled paper,CNTs,and Gel suggests potential applications in industrial fields,capitalizing on the biocompatible and biodegradable nature of cellulose.Density functional theory(DFT)calculations using the B3LYP with the 6-31G(d)basis set were employed to optimize the stability of these compounds and elucidate their chemical interactions.展开更多
Effectively separating bastnaesite from calcium-bearing gangue minerals(particularly calcite)presents a formidable challenge,making the development of efficient collectors crucial.To achieve this,we have designed and ...Effectively separating bastnaesite from calcium-bearing gangue minerals(particularly calcite)presents a formidable challenge,making the development of efficient collectors crucial.To achieve this,we have designed and synthesized a novel,highly efficient,water-soluble cationic collector,N-dodecylisopropanolamine(NDIA),for use in the bastnaesite-calcite flotation process.Density functional theory(DFT)calculations identified the amine nitrogen atom in NDIA as the site most susceptible to electrophilic attack and electron loss.By introducing an OH group into the traditional collector dodecylamine(DDA)structure,NDIA provided additional adsorption sites,enabling synergistic adsorption on the surface of bastnaesite,thereby significantly enhancing both the floatability and selectivity of these minerals.The recovery of bastnaesite was 76.02%,while the calcite was 1.26%.The NDIA markedly affected the zeta potential of bastnaesite,while its impact on calcite was relatively minor.Detailed Fourier-transform infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS)results elucidated that the―NH―and―OH groups in NDIA anchored onto the bastnaesite surface through robust electrostatic and hydrogen bonding interactions,thereby enhancing bastnaesite's affinity for NDIA.Furthermore,in situ atomic force microscopy(AFM)provided conclusive evidence of NDIA aggregation on the bastnaesite surface,improving contact angle and hydrophobicity,and significantly boosting the flotation recovery of bastnaesite.展开更多
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.
基金supported by the National Natural Science Foundation of China(Nos.22207036,22277034,22477034,and 22107033)Interdisciplinary Research Program of Huazhong University of Science and Technology(No.2023JCYJ037)International Cooperation Project of Hubei Provincial Key R&D Plan(No.2023EHA040)。
文摘Two pairs of novel 6/6/6/9 tetracyclic merosesquiterpenoid enantiomers,dauroxonanols A(1)and B(2),possessing an unprecedented 9,15-dioxatetracyclo[8.5.3.0^(4.17).0^(14.18)]octadecane core skeleton,were isolated from Rhododendron dauricum.The nuclear magnetic resonance(NMR)spectra of 1 and 2 showed very broad resonances,and^(13)C NMR spectrum of 1 exhibited only 13 instead of 22 carbon resonances.These broadening or missing NMR resonances led to a great challenge to elucidate their structures using NMR data analysis.Their structures and absolute configurations of 1 and 2 were finally determined by single crystal X-ray diffraction analysis,chiral separation,and electronic circular dichroism(ECD)calculations.Plausible biosynthetic pathways for 1 and 2 are proposed.Conformational analysis,density functional theory(DFT)calculations,and dynamic NMR assigned the coalescent NMR phenomena of 1 and 2 to the conformational changes of the flexible oxonane ring.Dauroxonanols A(1)and B(2)showed potentα-glucosidase inhibitory activities,2-8 times potent than acarbose,an antidiabetic drug targetingα-glucosidase in clinic.
基金supported by the National Key R&D Program of China(Grant Nos.2024-YFA1408303 and 2022YFA1403301)the National Natural Sciences Foundation of China(Grant Nos.12474247 and 92165204)+1 种基金support from Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)Research Center for Magnetoelectric Physicsof Guangdong Province(Grant No.2024B0303390001).
文摘Magnets exhibiting the Kitaev interaction,a bond-dependent magnetic interaction in honeycomb lattices,are generally regarded as promising candidates for hosting novel phenomena like quantum spin liquid states.However,realizing such magnets remains a significant challenge.Recently,some studies have suggested honeycomb magnets A_(3)Ni_(2)XO_(6)(A=Li,Na;X=Bi,Sb)with a high spin S=1 could serve as potential candidates for realizing strong Kitaev interactions.In this work,we systematically investigate their magnetic properties,with a particular emphasis on their Kitaev interactions,using first-principles calculations and Monte Carlo simulations.Our results indicate that all A_(3)Ni_(2)XO_(6)compounds are zigzag antiferromagnets,and their magnetic moments almost tend to be out of plane.We find that their dominant magnetic interactions are the nearest-neighbor ferromagnetic and third-nearest-neighbor antiferromagnetic Heisenberg interactions,while their Kitaev interactions are extremely weak.By analyzing their electronic structures and the mechanism of generating their magnetic interactions,we reveal that either artificially tuning spin-orbit coupling or applying strain cannot produce sufficient spin-orbit entangled states to realize the intriguing Kitaev interactions.Our work advances the understanding of the magnetism in A_(3)Ni_(2)XO_(6)compounds and provides insights for further exploration of Kitaev physics in honeycomb magnets.
基金supported and funded internally through Dr. Catherine Johnson's research funds at Missouri S&T
文摘This study investigates the application of Gurney and flight of fragment equations,typically used to predict metal fragment velocities,in modeling the water jet behavior.Three shotgun cartridge sizes were used as the energy source:2.59 g,5.83 g,and 7.13 g.Two configurations were tested:standard(full-barrel water load)and"negative 8"(partial water load).High-speed footage captured water column velocities,and Gurney models,including infinitely tamped and open-faced configurations,combined with the flight of fragment model were used to assess prediction accuracy.Results showed charge strength significantly affects water column velocity,with higher strengths yielding greater stability and velocity retention over distance.The infinitely tamped Gurney model closely predicted experimental velocities,deviating by as little as 1.4%for standard charges and 2.8% for negative 8 charges.Additionally,interesting dynamics such as a 1-2°rise in jet height and the rear overtaking the front was observed.These findings have significant implications for optimizing PAN disruptors and enhancing performance in high-velocity fluid applications and explosive breaching systems.
基金supported by the National Key R&D Program of China(Nos.2024YFE0109800 and 2024YFE0109802)the National Natural Science Foundation of China(Nos.12405141,12347106,12205340,and 12121005)+1 种基金the Gansu Natural Science Foundation(No.25JRRA467)the Key Research Program of the Chinese Academy of Sciences(No.XDPB15)。
文摘Neutron-rich boron,carbon,and nitrogen isotopes have garnered extensive experimental and theoretical interest.In the present work,we conducted a comprehensive study of these nuclei by utilizing ab initio valence-space in-medium similarity renormalization group calculations with chiral nucleon-nucleon and three-nucleon interactions.First,we systematically calculated the spectra of nuclei.Our results align well with the available experimental data,which are comparable to phenomenological shell model calculations.Subsequently,the evolution of the N=14 and N=16 shell gaps is discussed based on the calculated spectra and the effective single-particle energies.Our calculations suggest that the N=14 neutron subshell is present in the oxygen isotopes but disappears in the boron,carbon,and nitrogen isotopic chains.Moreover,the N=16 subshell is present in all isotopes but gradually decreases from^(24)O to^(21)B.These results provide valuable information for future studies.
基金supported by the National Key R&D Program of China(Nos.2024YFA1610900 and 2023YFA1606401)the National Natural Science Foundation of China(Nos.12335007 and 12035001)the United Kingdom Science and Technology Facilities Council(No.ST/V001108/1)。
文摘High multipole electromagnetic transitions are rare in nature.The highest-multipole transition observed in atomic nuclei is the electric hexacontatetrapole E6 transition from the T_(1/2)=2.54(2)-min J^(π)=1_(9/2)-isomer to the 7/2^(-)ground state in^(53)Fe with an angular momentum change of six units.In the present work,we performed ab initio calculations for this unique case by employing chiral effective field theory(EFT)forces.The in-medium similarity renormalization group is used to derive the valence-space effective Hamiltonian and multipolar transition operators.Bare nucleon charges were used in all the multipolar transition rate calculations,providing good agreement with the experimental data.The valence space takes the full fp shell.In^(53)Fe,the low-lying states were dominated by the 0f_(7/2)component.Two different versions of the chiral EFT two-plus three-nucleon interaction were used to test the dependence on the interaction used.We also tested the convergence of the transition rate calculations against the harmonic oscillator parameter hΩand basis truncations e_(max)and E_(3max)for twoand three-nucleon forces,respectively.
基金financially supported by the National Natural Science Foundation of China(No.52171141)the Fund of Natural Science Special(Special Post)Research Foundation of Guizhou University(No.2023-032)the Fund of Research Foundation of Guizhou University(No.2024-33)
文摘Currently,the development of high-efficiency two-dimensional(2D)transistors is still hindered by the limited availability of suitable semiconductors and the contact resistance between the metal contact and the 2D semiconductors.Endeavors to address these challenges are highly desired.In this study,we conducted a comprehensive exploration of the potential 2D transition metal dinitrides(TMN_(2)s,TM=all the 3d,4d and 5d transition metals)with hexagonal(h-)and trigonal(t-)phases through systematic first-principles calculations.Among all h-TMN_(2)s and t-TMN_(2)s structures,we identified 8 TMN_(2)s that exhibit dynamical and thermal stability at room temperature.Of these,the h-TiN_(2),h-ZrN_(2)and h-HfN_(2)arefound to be semiconductors,and their direct bang gap,calculated at the HSE06 level,are 1.48,1.96 and 2.64 eV,respectively.The electron and hole mobility(μ_(e)andμ_(h))of these three structures exceed 1×10^(4)and1×10^(3)cm^(2)·V^(-1)·s^(-1),respectively.Especially,theμeof h-TiN_(2)amounts to 2.5×10^(4)cm^(2)·V^(-1)·s^(-1),and theμhof h-ZrN_(2)reaches to 7.7×10^(3)cm^(2)·V^(-1)·s^(-1).Importantly,unlike the MoS_(2)system,h-TMN_(2)forms Ohm contacts with both transition metals(e.g.,Cu)and 2D metals(e.g.,graphene),with tunneling possibilities exceeding 50%in the Cu system.These outstanding intrinsic semiconductor properties and contact characteristics exhibited by h-TMN_(2)highlight the immense potential of transition metal dinitrides in driving the advancement of next-generation information devices.Our findings significantly broaden the range of 2D materials and provide valuable insights for the development of high-eficiency 2D information devices.
基金supported by the National Natural Science Foun-dation of China(Grant Nos.12393831 and 12088101).
文摘Control of hyperfine interaction strength of shallow donors in Si is one of the central issues in realizing Kane quantum computers.First-principles calculations on the hyperfine Stark shift of shallow donors are challenging since large supercells are needed to accommodate the delocalized donor wave functions.In this work,we investigated the hyperfine Stark shift and its strain tunability for shallow donors P and As in Si using the potential patching method based on first-principles density functional theory calculations.The good agreement between our calculations and experimental results confirms that the potential patching method is a feasible and accurate first-principles approach for studying wave-function-related properties of shallow impurities,such as the Stark shift parameter.It is further shown that the application of strain expands the range of hyperfine Stark shift and helps improve the response of shallow donor based qubit gates.The results could be useful for developing quantum computing architectures based on shallow donors in Si.
基金sponsored by Major Science and Technology Project of the Yunnan Provincial Department of Science and Technology(202502AB080011)Yunnan Province Industrial High-Tech Project(202403AA080015)Special Science and Technology Research Project of Yunnan Province for the South Asia and Southeast Asia Innovation Center(202403AP140006).
文摘Ag/Al_(2)O_(3) powders are highly effective catalytic materials utilized in the epoxidation of ethylene to produce ethylene oxide.One of the critical challenges in this catalytic process is the stability of nano-sized Ag particles,especially during high-temperature catalysis.However,this issue can be effectively addressed through in-situ reaction synthesis.To gain a deeper understanding of the underlying mechanisms,the phase transformation process and the thermodynamic mechanism of the oxidation reaction in the Ag/Al_(2)O_(3) system have been investigated using firstprinciples thermodynamic calculations in conjunction with traditional thermodynamic data.These calculations,whose accuracy has been verified,provide valuable insights into the behavior of Ag and Al under different conditions.The results indicate that,during AgAl solid-solution oxidation,Ag-containing Al preferentially forms the stable intermediate phase Ag2Al instead of undergoing direct oxidation;this pathway becomes thermodynamically more favorable at higher Ag concentrations.With increasing temperature,Ag2Al is further oxidized to yield Ag and Al_(2)O_(3).It is also found that above 237℃,Ag2O and AgAlO2 become unstable.The overall reaction pathway is solid solution→Ag2Al→Ag+Al_(2)O_(3).This comprehensive study provides a robust theoretical calculation basis for the development and optimization of in-situ reaction-synthesized Ag/Al_(2)O_(3) powder composite materials,which have significant potential for practical applications in catalysis.
基金Project(22376221)supported by the National Natural Science Foundation of ChinaProject(2024JJ2074)supported by the Natural Science Foundation of Hunan Province,ChinaProject(2023QNRC001)supported by the Young Elite Scientists Sponsorship Program by CAST。
文摘Understanding the adsorption behavior of heavy metals and metalloids on clay minerals is essential for remediating heavy metal-contaminated soils.The adsorption of heavy metals and metalloids on illite(001)and sodium montmorillonite(Na-MMT)(001)surfaces was investigated using first-principles calculations in this study,especially As atom and H_(3)AsO_(3) molecule.The adsorption energies of the As atom were−1.94 eV on the illite(001)and−0.56 eV on the Na-MMT(001),whereas,the adsorption energies of the H_(3)AsO_(3) molecule were−1.40 eV on illite(001)and−1.01 eV on Na-MMT(001).The above results indicate that the adsorption was more energetically favorable on illite(001).Additionally,compared to Na-MMT(001),there were more significant interactions between the atoms/molecules on the illite(001).After As atom and H_(3)AsO_(3) molecule adsorption,the electrons were transferred from mineral surface atoms to the adsorbates on both illite(001)and Na-MMT(001)surfaces.Moreover,the adsorption of As atom on illite(001)and Na-MMT(001)surfaces were more energy favorable compared to Hg,Cd,and Cr atoms.Overall,this work provides new insights into the adsorption behavior of As atoms and As molecules on illite and Na-MMT.The results indicate that illite rich soils are more prone to contamination by arsenic compared to soils primarily composed of Na-MMT minerals.
基金support from the National Natural Science Foundation of China(52174290).
文摘To explain the influence mechanism of MgO on the consolidation and reduction characteristics of roasted iron pellets,the properties and structure of pellets were investigated from multi-dimensions.It indicated that the MgO addition decreased the reduction swelling index(RSI)and reduction degree of pellets in both CO and H_(2)atmospheres.During the stepwise reduction process of Fe2O3→Fe3O4→FeO,the reduction behaviour of pellets in CO and H_(2)was similar,while the reduction rate of pellets in H_(2)atmosphere was almost twice as high as that in CO atmosphere.During the stepwise reduction process of FeO→Fe,the RSI of pellets showed a logarithmic increase in CO atmosphere and a linear decrease in H_(2)atmosphere.As investigated by first-principles calculations,C and Fe mainly formed chemical bonds,and the CO reduction process released energy,promoting the formation of iron whiskers.However,H and Fe produced weak physical adsorption,and the H_(2)reduction process was endothermic,inhibiting the generation of iron whiskers.With Mg2+doping in FexO,the nucleation region of iron whiskers expanded in CO reduction process,and the morphology of iron whiskers transformed from“slender”to“stocky,”reducing RSI of the pellets.
基金financially supported by the National Natural Science Foundation of China(No.51771044)the Natural Science Foundation of Hebei Province(No.E2019501061)+5 种基金the Performance Subsidy Fund for Key Laboratory of Dielectric and Electrolyte Functional Material Hebei(No.22567627H)the Fundamental Research Funds for the Central Universities(No.N2223025)2023 Hebei Provincial doctoral candidate Innovation Ability training funding project(CXZZBS2023165)the Programme of Introducing Talents of Discipline Innovation to Universities 2.0(No.BP0719037)the support of the Shanxi Supercomputing Center of China,the calculations for this work were performed on TianHe-2supported by the China Scholarship Council(CSC)。
文摘We have investigated the phase stability,magnetic properties,and martensitic transformation thermodynamics/kinetics of the Ni_(24-x)Mn_(18+x+y)Sn_(6-y)(x,y=0,1,2)system by combining the first-principles calculations and experiments.The calculation results show that the optimized lattice parameters are consistent with the experimental data.Respectively,we obtain the relation equation for the austenite formation energy(E_(form-A))and Mn content(X_(Mn)):E_(form-A)=507.358X_(Mn)-274.126,as well as for the six-layer modulated(6M)martensite formation energy(E_(form-6M))and Ni content(X_(Ni)):E_(form-6M)=-728.484X_(Ni)+264.374.The ternary phase diagram of the total magnetic moment was established.The excess Mn will reduce the total magnetic moment of 6M(Mag6M)and non-modulated(NM)(MagNM)martensites,with the following equations relating the total magnetic moment and Mn content:Mag_(6M)=-15.905X_(Mn)+7.902and Mag_(NM)=-14.781X_(Mn)+7.411,while the effect on austenite is complex.The variation of total magnetic moment is mainly dominated by the Mn atomic magnetic moment.The 3d electrons of Mn_(Sn)(Mn at Sn sublattice)play an important role in magnetic properties from the perspective of the electronic density of states.Based on the thermodynamics of martensitic transformation,the alloys will likely undergo austenite?6M?NM transformation sequence.Combining the thermodynamic and kinetic results,the martensitic transformation temperature decreases with x increasing and increases with y increasing.These results are expected to provide reference for predicting the phase stability and magnetic properties of NiMn-Sn alloys.
基金supported by the National Key R&D Program of China(No.2021YFB3701100)the Joint Funds of the National Natural Science Foundation of China(No.U22A20187)+4 种基金the Science and Technology Innovation Program of Hunan Province(Nos.2023RC3268,2021JC0005 and 2020RC4013)the Science Fund of State Key Laboratory of Advanced Design and Manu-facturing Technology for Vehicle(No.32117009)the Projects“Development of lightweight high-performance Mg alloys profiles manufacturing technologies”and“Research and development of room-temperature bendable Mg alloy thin sheets manufactur-ing technology”from QingHai Salt Lake Industry Co.,Ltd.(Nos.2022-Z-0810000000-21-ZC0609-0001 and 2022-Z-08)the“Technology Innovation 2025”Major Special Project of Ningbo CityThe first-principles calculations work was carried out using software provided by the High Performance Computing Center of Central South University.
文摘In the present work,a new Mg-Bi based alloy is developed by the addition of Zn and Ca in equiva-lent atom fraction with Bi.Mg-Bi and Mg-Bi-Zn-Ca alloys were prepared by extrusion at a ram speed of 20 mm/s.Room temperature mechanical properties and creep behaviors at 423 K were investigated.The results show that Zn and Ca co-addition shows little influence on average grain size and texture in-tensity but changes the dispersive Mg_(3)Bi_(2)into Mg_(2)Bi_(2)Ca particles in different sizes and a lower density.Twinning is largely activated during room-temperature deformation.Consequently,a slightly decreased proof strength but tripled elongation is shown at room temperature.Unexpectedly,large enhancement in creep resistance is detected after the co-alloying of Zn and Ca and the minimum creep rate is reduced by 10 to 20 times in the BZX621 alloy.Stress exponent n=4-5 indicates that the creep is a dislocation-climb controlled type.Post-mortem characterization on microstructure shows slip of dislocationc+aare also largely found in B6 as well as BZX621 alloy and cross-slip is detected more severe in B6 alloy.Dynamic segregation and precipitation are also seen in both alloys.Bi-clusters are seen dispersive across the grains in B6 and so did the PFZs that could undermine creep resistance at the grain boundaries.By contrast,Zn-rich needle-like precipitates are developed at most“ends”ofc+adislocations,which would hinder the further dislocation motions and thus improve the creep resistance.First-principles cal-culations were adopted and the results show that the thermal stability and thermomechanical properties of Mg_(2)Bi_(2)Ca are much better than that of Mg_(3)Bi_(2).Stacking faults energy is lowered down with the co-addition of Ca and Zn,which could inhibit the rate of dislocation climb and cross-slip.As a result,the im-proved creep resistance is obtained in the Mg-Bi-Zn-Ca alloys.Microstructural and controlling mechanism changes by thermal activation result in the unexpected enhancement in creep resistance with decreased room-temperature proof strength after co-addition.These findings could contribute to the development and optimization of creep-resistant Mg alloys in the future.
基金National Natural Science Foundation of China(No.51871175)111 project 2.0(No.BP0618008).
文摘Reducing the exploration of multi-principal element alloy space is a key challenge to design high-performance U-based high-entropy alloy(UHEA).Here,the best combination of multi-principal element can be efficiently acquired because proposed alloying strategy and screening criteria can substantially reduce the space of alloy and thus accelerate alloy design,rather than enormous random combinations through a trial-and-error approach.To choose the best seed alloy and suitable dopants,the screening criteria include small anisotropy,high specific modulus,high dynamical stability,and high ductility.We therefore find a shortcut to design UHEA from typical binary(UTi and UNb)to ternary(UTiNb),qua-ternary(UTiNbTa),and quinary(UTiNbTaFe).Finally,we find a best bcc senary UHEA(UTiNbTaFeMo),which has highest hardness and yield strength,while maintains good ductility among all the candidates.Compared to overestimation from empirical strength-hardness relationship,improved strength prediction can be achieved using a parameter-free theory considering volume mismatch and temperature effect on yield strength.This finding indicates that larger volume mismatch corresponds to higher yield strength,agreeing with the available measurements.Moreover,the dynamical stability and mechanical properties of candidates are greatly enhanced with increasing the number of multi-principal element,indicating the feasibility and effectiveness of adopted alloying strategy.The increasing of multi-principal element cor-responds to the increasing valence electron concentration(VEC).Alternatively,the mechanical properties significantly improve as increasing VEC,agreeing with measurements for other various bcc HEAs.This work can speed up research and development of advanced UHEA by greatly reducing the space of alloy composition.
基金financially supported by the National Key Research and Development Program of China,China(2022YFB3709300)Joint Lab for Electron Microscopy of Chongqing UniversityAnalytical and Testing Center of Chongqing University.
文摘Magnesium alloys have large reserves and good strength,attracting a lot of attention.Herein,the thermodynamic,elastic constants,and electronic properties of the Mg-Y-Zn ternary compounds were calculated;among them,MgYZn_(2) belongs to the cubic structure,MgYZn,Mg_(3)Y_(2)Zn_(4),and Mg_(14)YZn-1 belong to the hexagonal structure,Mg_(6)YZn-1,Mg_(6)YZn-2,MgY_(2)Zn,and Mg_(14)YZn-2 possess the orthorhombic structure,and Mg_(3)Y_(2)Zn_(3) is trigonal structure.The calculated cohesive energies of the results show that all compounds are thermodynamically stable.Moreover,the MgYZn_(2) compound exhibits the highest modulus of 76.84 MPa,and the Mg_(3)Y_(2)Zn_(3) has the biggest hardness of 6.6 GPa.In addition,the Mg_(6)YZn-2 has the strongest elastic anisotropic with A^(U) of 6.14 and A_(G) of 0.38,respectively.According to the population analysis,the Mg-Y covalent bond is due to the biggest bond population.The shortest weighted average bond length indicates that MgYZn_(2) has better elastic properties.Furthermore,the calculated limiting thermal conductivity results show that Mg_(14)YZn-2 has better thermal conductivity with maximum values of 0.94 W·m^(−1)·K^(−1) and 0.74 W·m^(−1)·K^(−1) for Clarke’s and Cahill’s models.
基金supported financially by the National Natural Science Foundation of China (No.22075028)。
文摘Rechargeable aluminum batteries with multi-electron reaction have a high theoretical capacity for next generation of energy storage devices. However, the diffusion mechanism and intrinsic property of Al insertion into MnO_(2) are not clear. Hence, based on the first-principles calculations, key influencing factors of slow Al-ions diffusion are narrow pathways, unstable Al-O bonds and Mn^(3+) type polaron have been identified by investigating four types of δ-MnO_(2)(O3, O'3, P2 and T1). Although Al insert into δ-MnO_(2) leads to a decrease in the spacing of the Mn-Mn layer, P2 type MnO_(2) keeps the long(spacious pathways)and stable(2.007–2.030 A) Al-O bonds resulting in the lower energy barrier of Al diffusion of 0.56 e V. By eliminated the influence of Mn^(3+)(low concentration of Al insertion), the energy barrier of Al migration achieves 0.19 e V in P2 type, confirming the obviously effect of Mn^(3+) polaron. On the contrary, although the T1 type MnO_(2) has the sluggish of Al-ions diffusion, the larger interlayer spacing of Mn-Mn layer,causing by H_(2)O could assist Al-ions diffusion. Furthermore, it is worth to notice that the multilayer δ-MnO_(2) achieves multi-electron reaction of 3|e|. Considering the requirement of high energy density, the average voltage of P2(1.76 V) is not an obstacle for application as cathode in RABs. These discover suggest that layered MnO_(2) should keep more P2-type structure in the synthesis of materials and increase the interlayer spacing of Mn-Mn layer for providing technical support of RABs in large-scale energy storage.
文摘This comprehensive review examines the structural,mechanical,electronic,and thermodynamic properties of Mg-Li-Al alloys,focusing on their corrosion resistance and mechanical performance enhancement.Utilizing first-principles calculations based on Density Functional Theory(DFT)and the quasi-harmonic approximation(QHA),the combined properties of the Mg-Li-Al phase are explored,revealing superior incompressibility,shear resistance,and stiffness compared to individual elements.The review highlights the brittleness of the alloy,supported by B/G ratios,Cauchy pressures,and Poisson’s ratios.Electronic structure analysis shows metallic behavior with varied covalent bonding characteristics,while Mulliken population analysis emphasizes significant electron transfer within the alloy.This paper also studied thermodynamic properties,including Debye temperature,heat capacity,enthalpy,free energy,and entropy,which are precisely examined,highlighting the Mg-Li-Al phase sensitive to thermal conductivity and thermal performance potential.Phonon density of states(PHDOS)confirms dynamic stability,while anisotropic sound velocities reveal elastic anisotropies.This comprehensive review not only consolidates the current understanding of the Mg-Li-Al alloy’s properties but also proposes innovative strategies for enhancing corrosion resistance.Among these strategies is the introduction of a corrosion barrier akin to the Mg-Li-Al network,which holds promise for advancing both the applications and performance of these alloys.This review serves as a crucial foundation for future research aimed at optimizing alloy design and processing methods.
文摘I had the privilege and the pleasure to work closely with Stephen J. Pennycook for about twenty years, having a group of post-docs and Vanderbilt-University graduate students embedded in his electron microscopy group at Oak Ridge National Laboratory, spending on average a day per week there. We combined atomic-resolution imaging of materials,electron-energy-loss spectroscopy, and density-functional-theory calculations to explore and elucidate diverse materials phenomena, often resolving long-standing issues. This paper is a personal perspective of that journey, highlighting a few examples to illustrate the power of combining theory and microscopy and closing with an assessment of future prospects.
基金The research received funding from the PRIMA International Project,between the Academy of Scientific Research and Technology(ASRT)and PRIMA,through the Joint Agreement Project“Sustainable Antimicrobial Packaging Based on a Healthy Intelligent Renewable Approach”with acronym“SAPHIRA”.
文摘Fire retardant CNTs/WPP/Gel composite papers were fabricated by incorporating bio-based carbon nanotubes(CNTs)recycled from mature beech pinewood sawdust(MB)and cellulosic waste printed paper(WPP)into a gelatin solution(Gel)and allowing the mixture to dry at room temperature.The CNTs within the WPP matrix formed a network,enhancing the mechanical and thermal properties of the resulting CNTs paper sheet.In comparison to pure WPP/Gel,CNTs/WPP/Gel exhibited superior flexibility,mechanical toughness,and notable flame retardancy characteristics.This study provides a unique and practical method for producing flame-retardant CNTs/WPP/Gel sheets,suitable for diverse industrial applications,especially packaging,where used paper materials pose a significant fire risk.Bio-CNT-based fire-resistant packaging offers enhanced safety during transportation and storage.The sheets demonstrated increased strength and stiffness,with optimal mechanical properties achieved at a 20%CNTs loading.Additionally,thermal stability was improved,as confirmed by thermogravimetric analysis(TGA)and differential thermogravimetry(DTG).Flame retardancy tests revealed a rise in LOI(Limiting Oxygen Index)values with increasing CNTs content,indicating the CNTs’effectiveness in inhibiting combustion.The compatibility of recycled paper,CNTs,and Gel suggests potential applications in industrial fields,capitalizing on the biocompatible and biodegradable nature of cellulose.Density functional theory(DFT)calculations using the B3LYP with the 6-31G(d)basis set were employed to optimize the stability of these compounds and elucidate their chemical interactions.
基金supported by the the National Key R&D Program of China(No.2021YFC2900800)National Natural Science Foundation of China(Nos.52425406,51874247,51922091,and 52204285)+4 种基金the Open Research Fund of State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization(No.CNMRCUKF2001)Science and Technology Major Project of Ordos City-Iconic Innovation Team and “Rejuvenating Inner Mongolia through Science and Technology”(No.202204/2023)Yueqi Outstanding Scholar Award of CUMTB(No.202022)Funded by Open Foundation of State Key Laboratory of Mineral Processing(No.BGRIMM-KJSKL-2023-05)Fundamental Research Funds for the Central Universities(Ph.D.Top Innovative Talents Fund of CUMT BBJ2024048)。
文摘Effectively separating bastnaesite from calcium-bearing gangue minerals(particularly calcite)presents a formidable challenge,making the development of efficient collectors crucial.To achieve this,we have designed and synthesized a novel,highly efficient,water-soluble cationic collector,N-dodecylisopropanolamine(NDIA),for use in the bastnaesite-calcite flotation process.Density functional theory(DFT)calculations identified the amine nitrogen atom in NDIA as the site most susceptible to electrophilic attack and electron loss.By introducing an OH group into the traditional collector dodecylamine(DDA)structure,NDIA provided additional adsorption sites,enabling synergistic adsorption on the surface of bastnaesite,thereby significantly enhancing both the floatability and selectivity of these minerals.The recovery of bastnaesite was 76.02%,while the calcite was 1.26%.The NDIA markedly affected the zeta potential of bastnaesite,while its impact on calcite was relatively minor.Detailed Fourier-transform infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS)results elucidated that the―NH―and―OH groups in NDIA anchored onto the bastnaesite surface through robust electrostatic and hydrogen bonding interactions,thereby enhancing bastnaesite's affinity for NDIA.Furthermore,in situ atomic force microscopy(AFM)provided conclusive evidence of NDIA aggregation on the bastnaesite surface,improving contact angle and hydrophobicity,and significantly boosting the flotation recovery of bastnaesite.
