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
In this study,6061 aluminum alloy and galvanized steel fusion-brazed lap joints were obtained using a laser-arc hybrid heat source,and the effects of laser power variation on the microstructure,mechanical properties,a...In this study,6061 aluminum alloy and galvanized steel fusion-brazed lap joints were obtained using a laser-arc hybrid heat source,and the effects of laser power variation on the microstructure,mechanical properties,and fracture mechanism of the joints were ana-lyzed.The results showed that the tensile shear load initially increased with rising laser power,followed by a decrease.At a laser power of 240 W,the maximum tensile shear load was 2479.8 N/cm and the weak section of joint was in the Al-Fe reaction layer con-sisting of Fe(Al,Si)_(3),Fe_(2)(Al,Si)_(5),and Fe(Al,Si)intermetallic compounds(IMCs).Computational results showed that the inherently high brittleness and hardness of Fe(Al,Si)_(3) and the high mismatch rates of Fe(Al,Si)_(3)/Al interfaces were the key factor leading to the failure of the joints at lower heat input.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
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
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
Based on experiments and first-principles calculations,the microstructures and mechanical properties of as-cast and solution treated Mg-10Gd-4Y-xZn-0.6Zr(x=0,1,2,wt.%)alloys are investigated.The transformation process...Based on experiments and first-principles calculations,the microstructures and mechanical properties of as-cast and solution treated Mg-10Gd-4Y-xZn-0.6Zr(x=0,1,2,wt.%)alloys are investigated.The transformation process of long-period stacking ordered(LPSO)structure during solidification and heat treatment and its effect on the mechanical properties of experimental alloys are discussed.Results reveal that the stacking faults and 18R LPSO phases appear in the as-cast Mg-10Gd-4Y-1Zn-0.6Zr and Mg-10Gd-4Y-2Zn-0.6Zr alloys,respectively.After solution treatment,the stacking faults and 18R LPSO phase transform into 14H LPSO phase.The Enthalpies of formation and reaction energy of 14H and 18R LPSO are calculated based on first-principles.Results show that the alloying ability of 18R is stronger than that of 14H.The reaction energies show that the 14H LPSO phase is more stable than the 18R LPSO.The elastic properties of the 14H and 18R LPSO phases are also evaluated by first-principles calculations,and the results are in good agreement with the experimental results.The precipitation of LPSO phase improves the tensile strength,yield strength and elongation of the alloy.After solution treatment,the Mg-10Gd-4Y-2Zn-0.6Zr alloy has the best mechanical properties,and its ultimate tensile strength and yield strength are 278.7 MPa and 196.4 MPa,respectively.The elongation of Mg-10Gd-4Y-2Zn-0.6Zr reaches 15.1,which is higher than that of Mg-10Gd-4Y0.6Zr alloy.The improving mechanism of elastic modulus by the LPSO phases and the influence on the alloy mechanical properties are also analyzed.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
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
Superconducting materials with high critical temperature have the potential to revolutionize many fields,including military,electronic communications,and power energy.Therefore,scientists around the world have been ti...Superconducting materials with high critical temperature have the potential to revolutionize many fields,including military,electronic communications,and power energy.Therefore,scientists around the world have been tirelessly working with the ultimate goal of achieving high-temperature superconductivity.In 2023,a preprint by Lee et al.in South Korea claimed the discovery of ultra-high-temperature superconductivity with a critical temperature of up to 423 K in Cu-doped lead-apatite(LK-99)(arXiv:2307.12008,arXiv:2307.12037),which caused a worldwide sensation and attention.Herein,the electronic structures,phonon dynamics,and electrical conductivities of LK-99 and its parent compound lead-apatite have been calculated using first-principles methods.The results show that the lead-apatite compound and the LK-99 compound are insulator and half-metal respectively.The flat band characteristic is consistent with previous calculations.The electrical conductivity of the LK-99 compound shows two extreme points,and the electrical conductivity along the C-axis increases significantly after 400 K.The phonon dispersion spectra of the compounds were investigated,demonstrating their dynamic instability.展开更多
The electronic and topological properties of FeGe2 with a tetragonal crystal structure were investigated via first-principles calculations.The results demonstrate that FeGe2 in this structure exhibits anti-ferromagnet...The electronic and topological properties of FeGe2 with a tetragonal crystal structure were investigated via first-principles calculations.The results demonstrate that FeGe2 in this structure exhibits anti-ferromagnetism,with two bands crossing the Fermi level nesting each other at high-symmetry points in the Brillouin zone,forming a nodal ring where the nodes intersect in momentum space.Additionally,it possesses nontrivial topological surface states.Upon inclusion of SOC(spin-orbit coupling),there are no significant changes observed in the band structure,nodal features,or surface states,indicating the persistence of its topological nodal-line characteristics.展开更多
In this work,Mg(0001)/AlB_(2)(0001)interfaces with various terminations and stacking orders were constructed,and the atomic and electronic structures and adhesion work(Wad)of the interface were investigated using the ...In this work,Mg(0001)/AlB_(2)(0001)interfaces with various terminations and stacking orders were constructed,and the atomic and electronic structures and adhesion work(Wad)of the interface were investigated using the first-principles calculations.Notably,during the geometry optimization process,the B-mid-top(B-MT)Mg(0001)/AlB_(2)(0001)interface exhibits the most significant interface changes and manifests the least stability.Horizontal movement of Mg atoms in the first layer of the Mg surface slab,along the normal direction,results in a structure akin to the structurally optimized hexagonal close-packed(HCP)interface.The B-HCP interface demonstrates the highest stability,the largest ideal Wad,and the smallest interface distance.The interface enhances the binding strength of the Mg-side sub-interface,but diminishes the binding strength of the AlB_(2)-side sub-interface.Furthermore,Mg atoms can form metallic/covalent mixed bonds with Al atoms on the Al-terminal AlB_(2) surface and form ionic bonds with B atoms on the B-terminal AlB_(2) surface.Mg(0001)/AlB_(2)(0001)interface has good bonding properties.This research provides strong theoretical support for an in-depth understanding of Mg/AlB_(2) interface characteristics.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
Recent technical progress in the industry has led to an urgent requirement on new materials with enhanced multi-properties.To meet this multi-property requirement,the materials consisting of three and more elements ha...Recent technical progress in the industry has led to an urgent requirement on new materials with enhanced multi-properties.To meet this multi-property requirement,the materials consisting of three and more elements have attracted increasing attention.However,facing to the nearly unknown huge multi-component materials system,the traditional trial and error method cannot provide sufficient data efficiently.Therefore,an efficient material innovation strategy is significant.The first-principles calculation based on the density functional theory is a powerful tool for both the accurate prediction of material properties and the identification of its underlying thermodynamics and dynamics.At the same time,the advances of computational methods and computer calculation abilities that are orders of magnitude faster than before make the high throughput first-principles calculations popular.At present,the simulation-assisted material design has become a main branch in the material research field and a great many successes have been made.In this article,the advances of the high throughput first-principles calculations are reviewed to show the achievements of the first-principles calculations and guide the future directions of its applications in ceramics.展开更多
Electronic structure and elastic properties of MgCu_(2),Mg_(2)Ca and MgZn_(2)phases were investigated by means of first-principles calculations from CASTEP program based on density functional theory(DFT).The calculate...Electronic structure and elastic properties of MgCu_(2),Mg_(2)Ca and MgZn_(2)phases were investigated by means of first-principles calculations from CASTEP program based on density functional theory(DFT).The calculated lattice parameters were in good agreement with the experimental and literature values.The calculated heats of formation and cohesive energies shown that MgCu_(2)has the strongest alloying ability and structural stability.The elastic constants of MgCu_(2),Mg_(2)Ca and MgZn_(2)phases were calculated,the bulk moduli,shear moduli,Young's moduli and Poisson's ratio were derived.The calculated results shown that MgCu_(2),Mg_(2)Ca and MgZn_(2)are all ductile phases.Among the three phases,MgCu_(2)has the strongest stiffness and the plasticity of MgZn_(2)phase is the best.The density of states(DOS),Mulliken electron occupation number and charge density difference of MgCu_(2),Mg_(2)Ca and MgZn_(2)phases were discussed to analyze the mechanism of structural stability and mechanical properties.展开更多
Herein,the effects of 33 alloying elements on the elastic properties and solid solution strengthening(SSS)of a-Ti alloys were systematically studied via first-principles calculations based on a dilute solid solution.A...Herein,the effects of 33 alloying elements on the elastic properties and solid solution strengthening(SSS)of a-Ti alloys were systematically studied via first-principles calculations based on a dilute solid solution.All alloying elements in these calculations were thermodynamically favorable,which indicated that these elements could be dissolved inα-Ti alloys.Ti_(35)Os had the highest elastic modulus as compared to those of other dilute Tibased solid solutions.Au,Co,and Pt were found to be promising candidates for improving the ductilities ofα-Ti solid solution alloys.Solid solution strengthening was analyzed using Cottrell's and Labush's models.Based on the solid solubility,Ir,Rh,Ni,and Pt were found to possess the best solid solution hardening effects in the following order:Ir>Rh>Ni>Pt.The bonding state between Ti and the impurity atom was visually characterized owing to the difference between their charge densities.By integrating the calculations of mean bond length and mean population,the results showed that Ti-Os had the largest mean population and degree of delocalization of the electron cloud around the solute atom,implying ionic characteristics of Os and Ti.Furthermore,after analyzing the alloying elements of each group,we found thatⅧ-group elements(Ru,Rh,Pd,Os,Ir,Pt)had good potentials for improving the comprehensive mechanical properties of Ti alloys.展开更多
Effects of pressure on lattice parameters, electronic, thermodynamic and mechanical properties of the fully ordered Ti_(2)AlNb orthorhombic phase were studied using first-principles calculations based on density funct...Effects of pressure on lattice parameters, electronic, thermodynamic and mechanical properties of the fully ordered Ti_(2)AlNb orthorhombic phase were studied using first-principles calculations based on density functional theory(DFT). The bonding nature for ordering orthorhombic Ti_(2)AlNb was revealed quantitatively through the electronic structure analyzing. The external pressures play limited roles in the elastic anisotropy of the alloy due to the outstanding dynamical and mechanical stabilities under pressure. However, the shear modulus of O phase manifests anisotropic, where {010} shear planes are the easiest planes to cleave among the principal planes under all pressures.The heat capacities, volume expansions and thermal expansion coefficients were calculated using the quasi-harmonic approximation model based on the phonon dispersion curves. Meanwhile, the bulk modulus, Young’s modulus,shear modulus and the hardness are promptly enhanced under pressure. The predicted results give hints to design Ti_(2)AlNb-based alloy as high-pressure applications.展开更多
To clarify the effect of pressure on a(TaNb)0.67(HfZrTi)0.33 alloy composed of a solid solution with a single body-centered-cubic crystal structure,we used first-principles calculations to theoretically investigate th...To clarify the effect of pressure on a(TaNb)0.67(HfZrTi)0.33 alloy composed of a solid solution with a single body-centered-cubic crystal structure,we used first-principles calculations to theoretically investigate the structural,elastic,and electronic properties of this alloy at different pressures.The results show that the calculated equilibrium lattice parameters are consistent with the experimental results,and that the normalized structural parameters of lattice constants and volume decrease whereas the total enthalpy differenceΔE and elastic constants increase with increasing pressure.The(TaNb)0.67(HfZrTi)0.33 alloy exhibits mechanical stability at high pressures lower than 400 GPa.At high pressure,the bulk modulus B shows larger values than the shear modulus G,and the alloy exhibits an obvious anisotropic feature at pressures ranging from 30 to 70 GPa.Our analysis of the electronic structures reveals that the atomic orbitals are occupied by the electrons change due to the compression of the crystal lattices under the effect of high pressure,which results in a decrease in the total density of states and a wider electron energy level.This factor is favorable for zero resistance.展开更多
The variation of stacking fault energy(SFE)in a number of binary Cu alloys is predicted through considering the Suzuki segregation by the full potential linearly augmented plane wave(FPLAPW)method.The calculated resul...The variation of stacking fault energy(SFE)in a number of binary Cu alloys is predicted through considering the Suzuki segregation by the full potential linearly augmented plane wave(FPLAPW)method.The calculated results show that some solute atoms(Mg,Al,Si,Zn,Ga,Ge,Cd,Sn,and Pb),which prefer to form the Suzuki segregation,may decrease the value of SFE;while the others(Ti,Mn,Fe,Ni,Zr,Ag,and Au),which do not cause the Suzuki segregation may not decrease the SFE.Furthermore,it is interesting to find that the former alloying elements are located on the right of Cu group while the latter on the left of Cu group in the periodic table of elements.The intrinsic reasons for the new findings can be traced down to the valences electronic structure of solute and Cu atoms,i.e.,the similarity of valence electronic structure between solute and Cu atoms increases the value of SFE,while the difference decreases the value of SFE.展开更多
The structural, electronic, optical and thermodynamic properties of Mo2Ga2C are investigated using density func- tional theory （DFT） within the generalized gradient approximation （GGA）. The optimized crystal struc...The structural, electronic, optical and thermodynamic properties of Mo2Ga2C are investigated using density func- tional theory （DFT） within the generalized gradient approximation （GGA）. The optimized crystal structure is obtained and the lattice parameters are compared with available experimental data. The electronic density of states （DOS） is calculated and analyzed. The metallic behavior for the compound is confirmed and the value of DOS at Fermi level is 4.2 states per unit cell per eV. Technologically important optical parameters （e.g., dielectric function, refractive index, absorption coefficient, photo conductivity, reflectivity, and loss function） are calculated for the first time. The study of dielectric constant （ε1） indicates the Drude-like behavior. The absorption and conductivity spectra suggest that the compound is metallic. The reflectance spectrum shows that this compound has the potential to be used as a solar reflector. The thermodynamic properties such as the temperature and pressure dependent bulk modulus, Debye temperature, specific heats, and thermal expansion coefficient of Mo2Ga2C MAX phase are derived from the quasi-harmonic Debye model with phononic effect also for the first time. Analysis of Tc expression using available parameter values （DOS, Debye temperature, atomic mass, etc.） suggests that the compound is less likely to be superconductor.展开更多
In this work,the effects of Co doping on the magnetostructural coupling transformation of Ni_(50-x)Co_(x)Mn_(50-y)Ti_(y)(x=0-15,y=12.5-15)Heusler alloys were systematically investigated through the first-princi-ples c...In this work,the effects of Co doping on the magnetostructural coupling transformation of Ni_(50-x)Co_(x)Mn_(50-y)Ti_(y)(x=0-15,y=12.5-15)Heusler alloys were systematically investigated through the first-princi-ples calculations and experimental verification.The cal-culation result indicates that the doped Co atoms prefer to occupy the Ni sublattice.The Co atoms tend to flock together in terms of the lowest energy principle.Since the formation energy of the austenite is higher than that of the martensite,the alloys will undergo martensitic transfor-mation for the Ni_(50-x)Co_(x)Mn_(37.5)Ti_(12.5)alloys(x=0-12.5).The magnetostructural coupling point of Ni_(50-x)Co_(x)Mn_(37.5)Ti_(12.5)alloys is predicted in the vicinity of x=11-12.Based on the computational composition Ni_(37.5)Co_(12.5)Mn_(37.5)Ti_(12.5),the Ni_(36)Co_(14)Mn_(36)Ti_(14)alloy with magnetostructural coupling near room temperature was experimentally developed by simultaneously increasing the Ti and Co contents.The largest magnetization change(ΔM)and magnetic entropy changes(ΔS_(m))obtained under magnetic field of 5 T for the martensitic transformation in the Ni_(36)Co_(14)Mn_(36)Ti_(14) alloy are about 87.6 A·m^(2)·kg^(-1)and 21 J·kg^(-1)·K^(-1),respectively.The fracture strength and strain for non-textured polycrystalline Ni_(36)Co_(14)Mn_(36)Ti_(14)alloy reach 953 MPa and 12.3%,respectively.The results show that the alloy not only possesses a large magne-tocaloric effect but also has excellent mechanical proper-ties.In addition,the 6 M modulated martensite is evidenced in the Ni-Co-Mn-Ti alloys via transmission electron microscopy technique.展开更多
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supported by the National Key Research and Development Program of China(No.2022YFB4600900).
文摘In this study,6061 aluminum alloy and galvanized steel fusion-brazed lap joints were obtained using a laser-arc hybrid heat source,and the effects of laser power variation on the microstructure,mechanical properties,and fracture mechanism of the joints were ana-lyzed.The results showed that the tensile shear load initially increased with rising laser power,followed by a decrease.At a laser power of 240 W,the maximum tensile shear load was 2479.8 N/cm and the weak section of joint was in the Al-Fe reaction layer con-sisting of Fe(Al,Si)_(3),Fe_(2)(Al,Si)_(5),and Fe(Al,Si)intermetallic compounds(IMCs).Computational results showed that the inherently high brittleness and hardness of Fe(Al,Si)_(3) and the high mismatch rates of Fe(Al,Si)_(3)/Al interfaces were the key factor leading to the failure of the joints at lower heat input.
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 Research and Development Program of China[grant No.2018YFB2001800]National Natural Science Foundation of China[grant No.51871184]Dalian High-level Talents Innovation Support Program[grant No.2021RD06]。
文摘Based on experiments and first-principles calculations,the microstructures and mechanical properties of as-cast and solution treated Mg-10Gd-4Y-xZn-0.6Zr(x=0,1,2,wt.%)alloys are investigated.The transformation process of long-period stacking ordered(LPSO)structure during solidification and heat treatment and its effect on the mechanical properties of experimental alloys are discussed.Results reveal that the stacking faults and 18R LPSO phases appear in the as-cast Mg-10Gd-4Y-1Zn-0.6Zr and Mg-10Gd-4Y-2Zn-0.6Zr alloys,respectively.After solution treatment,the stacking faults and 18R LPSO phase transform into 14H LPSO phase.The Enthalpies of formation and reaction energy of 14H and 18R LPSO are calculated based on first-principles.Results show that the alloying ability of 18R is stronger than that of 14H.The reaction energies show that the 14H LPSO phase is more stable than the 18R LPSO.The elastic properties of the 14H and 18R LPSO phases are also evaluated by first-principles calculations,and the results are in good agreement with the experimental results.The precipitation of LPSO phase improves the tensile strength,yield strength and elongation of the alloy.After solution treatment,the Mg-10Gd-4Y-2Zn-0.6Zr alloy has the best mechanical properties,and its ultimate tensile strength and yield strength are 278.7 MPa and 196.4 MPa,respectively.The elongation of Mg-10Gd-4Y-2Zn-0.6Zr reaches 15.1,which is higher than that of Mg-10Gd-4Y0.6Zr alloy.The improving mechanism of elastic modulus by the LPSO phases and the influence on the alloy mechanical properties are also analyzed.
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 by the National Natural Science Foun-dation of China(Nos.11921006,11975034,11375018,12005048,12335017,U20B2025,and U21B2082)the Beijing Municipal Natural Science Foundation(1222023)the Shenzhen Science and Technology Program(RCYK20210609103904028).
文摘Superconducting materials with high critical temperature have the potential to revolutionize many fields,including military,electronic communications,and power energy.Therefore,scientists around the world have been tirelessly working with the ultimate goal of achieving high-temperature superconductivity.In 2023,a preprint by Lee et al.in South Korea claimed the discovery of ultra-high-temperature superconductivity with a critical temperature of up to 423 K in Cu-doped lead-apatite(LK-99)(arXiv:2307.12008,arXiv:2307.12037),which caused a worldwide sensation and attention.Herein,the electronic structures,phonon dynamics,and electrical conductivities of LK-99 and its parent compound lead-apatite have been calculated using first-principles methods.The results show that the lead-apatite compound and the LK-99 compound are insulator and half-metal respectively.The flat band characteristic is consistent with previous calculations.The electrical conductivity of the LK-99 compound shows two extreme points,and the electrical conductivity along the C-axis increases significantly after 400 K.The phonon dispersion spectra of the compounds were investigated,demonstrating their dynamic instability.
文摘The electronic and topological properties of FeGe2 with a tetragonal crystal structure were investigated via first-principles calculations.The results demonstrate that FeGe2 in this structure exhibits anti-ferromagnetism,with two bands crossing the Fermi level nesting each other at high-symmetry points in the Brillouin zone,forming a nodal ring where the nodes intersect in momentum space.Additionally,it possesses nontrivial topological surface states.Upon inclusion of SOC(spin-orbit coupling),there are no significant changes observed in the band structure,nodal features,or surface states,indicating the persistence of its topological nodal-line characteristics.
基金supported by the Innovation Team Cultivation Project of Yunnan Province under Grant No.202005AE160016the Key Research&Development Program of Yunnan Province under Grant No.202103AA080017.
文摘In this work,Mg(0001)/AlB_(2)(0001)interfaces with various terminations and stacking orders were constructed,and the atomic and electronic structures and adhesion work(Wad)of the interface were investigated using the first-principles calculations.Notably,during the geometry optimization process,the B-mid-top(B-MT)Mg(0001)/AlB_(2)(0001)interface exhibits the most significant interface changes and manifests the least stability.Horizontal movement of Mg atoms in the first layer of the Mg surface slab,along the normal direction,results in a structure akin to the structurally optimized hexagonal close-packed(HCP)interface.The B-HCP interface demonstrates the highest stability,the largest ideal Wad,and the smallest interface distance.The interface enhances the binding strength of the Mg-side sub-interface,but diminishes the binding strength of the AlB_(2)-side sub-interface.Furthermore,Mg atoms can form metallic/covalent mixed bonds with Al atoms on the Al-terminal AlB_(2) surface and form ionic bonds with B atoms on the B-terminal AlB_(2) surface.Mg(0001)/AlB_(2)(0001)interface has good bonding properties.This research provides strong theoretical support for an in-depth understanding of Mg/AlB_(2) interface characteristics.
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 Natural Science Foundation of Shanghai(No.20ZR1419200)the National Natural Science Foundation of China(No.51972089)the Program for Professor of Special Appointment(Eastern Scholar)by Shanghai Municipal Education Commission(No.TP2015040)。
文摘Recent technical progress in the industry has led to an urgent requirement on new materials with enhanced multi-properties.To meet this multi-property requirement,the materials consisting of three and more elements have attracted increasing attention.However,facing to the nearly unknown huge multi-component materials system,the traditional trial and error method cannot provide sufficient data efficiently.Therefore,an efficient material innovation strategy is significant.The first-principles calculation based on the density functional theory is a powerful tool for both the accurate prediction of material properties and the identification of its underlying thermodynamics and dynamics.At the same time,the advances of computational methods and computer calculation abilities that are orders of magnitude faster than before make the high throughput first-principles calculations popular.At present,the simulation-assisted material design has become a main branch in the material research field and a great many successes have been made.In this article,the advances of the high throughput first-principles calculations are reviewed to show the achievements of the first-principles calculations and guide the future directions of its applications in ceramics.
基金This work is supported by National Key Technology Research and Development Program of Ministry of Science and Technology of China(2011BAE22B00)Program for Liaoning Innovative Research Team in University.
文摘Electronic structure and elastic properties of MgCu_(2),Mg_(2)Ca and MgZn_(2)phases were investigated by means of first-principles calculations from CASTEP program based on density functional theory(DFT).The calculated lattice parameters were in good agreement with the experimental and literature values.The calculated heats of formation and cohesive energies shown that MgCu_(2)has the strongest alloying ability and structural stability.The elastic constants of MgCu_(2),Mg_(2)Ca and MgZn_(2)phases were calculated,the bulk moduli,shear moduli,Young's moduli and Poisson's ratio were derived.The calculated results shown that MgCu_(2),Mg_(2)Ca and MgZn_(2)are all ductile phases.Among the three phases,MgCu_(2)has the strongest stiffness and the plasticity of MgZn_(2)phase is the best.The density of states(DOS),Mulliken electron occupation number and charge density difference of MgCu_(2),Mg_(2)Ca and MgZn_(2)phases were discussed to analyze the mechanism of structural stability and mechanical properties.
基金financially supported by the Rare and Precious Metals Material Genetic Engineering Project of Yunnan Province (No.202002AB080001-3)the National Natural Science Foundation of China (No.52001150)
文摘Herein,the effects of 33 alloying elements on the elastic properties and solid solution strengthening(SSS)of a-Ti alloys were systematically studied via first-principles calculations based on a dilute solid solution.All alloying elements in these calculations were thermodynamically favorable,which indicated that these elements could be dissolved inα-Ti alloys.Ti_(35)Os had the highest elastic modulus as compared to those of other dilute Tibased solid solutions.Au,Co,and Pt were found to be promising candidates for improving the ductilities ofα-Ti solid solution alloys.Solid solution strengthening was analyzed using Cottrell's and Labush's models.Based on the solid solubility,Ir,Rh,Ni,and Pt were found to possess the best solid solution hardening effects in the following order:Ir>Rh>Ni>Pt.The bonding state between Ti and the impurity atom was visually characterized owing to the difference between their charge densities.By integrating the calculations of mean bond length and mean population,the results showed that Ti-Os had the largest mean population and degree of delocalization of the electron cloud around the solute atom,implying ionic characteristics of Os and Ti.Furthermore,after analyzing the alloying elements of each group,we found thatⅧ-group elements(Ru,Rh,Pd,Os,Ir,Pt)had good potentials for improving the comprehensive mechanical properties of Ti alloys.
基金financially supported by the National Natural Science Foundation of China (Nos.50971043 and 51171046)the Research Fund for the Doctoral Program of Higher Education of China (No.20133514110006)+1 种基金the Natural Science Foundation of Fujian Province,China (No.2014J01176)the Program for New Century Excellent Talents in University of Fujian Province,China (No.JA10013)。
文摘Effects of pressure on lattice parameters, electronic, thermodynamic and mechanical properties of the fully ordered Ti_(2)AlNb orthorhombic phase were studied using first-principles calculations based on density functional theory(DFT). The bonding nature for ordering orthorhombic Ti_(2)AlNb was revealed quantitatively through the electronic structure analyzing. The external pressures play limited roles in the elastic anisotropy of the alloy due to the outstanding dynamical and mechanical stabilities under pressure. However, the shear modulus of O phase manifests anisotropic, where {010} shear planes are the easiest planes to cleave among the principal planes under all pressures.The heat capacities, volume expansions and thermal expansion coefficients were calculated using the quasi-harmonic approximation model based on the phonon dispersion curves. Meanwhile, the bulk modulus, Young’s modulus,shear modulus and the hardness are promptly enhanced under pressure. The predicted results give hints to design Ti_(2)AlNb-based alloy as high-pressure applications.
基金the National Natural Science Foundation of China(No.51701128)the Scientific Research Project of Education Department of Liaoning Province,China(No.JYT19037).
文摘To clarify the effect of pressure on a(TaNb)0.67(HfZrTi)0.33 alloy composed of a solid solution with a single body-centered-cubic crystal structure,we used first-principles calculations to theoretically investigate the structural,elastic,and electronic properties of this alloy at different pressures.The results show that the calculated equilibrium lattice parameters are consistent with the experimental results,and that the normalized structural parameters of lattice constants and volume decrease whereas the total enthalpy differenceΔE and elastic constants increase with increasing pressure.The(TaNb)0.67(HfZrTi)0.33 alloy exhibits mechanical stability at high pressures lower than 400 GPa.At high pressure,the bulk modulus B shows larger values than the shear modulus G,and the alloy exhibits an obvious anisotropic feature at pressures ranging from 30 to 70 GPa.Our analysis of the electronic structures reveals that the atomic orbitals are occupied by the electrons change due to the compression of the crystal lattices under the effect of high pressure,which results in a decrease in the total density of states and a wider electron energy level.This factor is favorable for zero resistance.
基金financially supported by the National Natural Science Foundation of China(Nos.51871223,51571198 and 51790482)the LiaoNing Revitalization Talents Program(No.XLYC1808027)。
文摘The variation of stacking fault energy(SFE)in a number of binary Cu alloys is predicted through considering the Suzuki segregation by the full potential linearly augmented plane wave(FPLAPW)method.The calculated results show that some solute atoms(Mg,Al,Si,Zn,Ga,Ge,Cd,Sn,and Pb),which prefer to form the Suzuki segregation,may decrease the value of SFE;while the others(Ti,Mn,Fe,Ni,Zr,Ag,and Au),which do not cause the Suzuki segregation may not decrease the SFE.Furthermore,it is interesting to find that the former alloying elements are located on the right of Cu group while the latter on the left of Cu group in the periodic table of elements.The intrinsic reasons for the new findings can be traced down to the valences electronic structure of solute and Cu atoms,i.e.,the similarity of valence electronic structure between solute and Cu atoms increases the value of SFE,while the difference decreases the value of SFE.
文摘The structural, electronic, optical and thermodynamic properties of Mo2Ga2C are investigated using density func- tional theory （DFT） within the generalized gradient approximation （GGA）. The optimized crystal structure is obtained and the lattice parameters are compared with available experimental data. The electronic density of states （DOS） is calculated and analyzed. The metallic behavior for the compound is confirmed and the value of DOS at Fermi level is 4.2 states per unit cell per eV. Technologically important optical parameters （e.g., dielectric function, refractive index, absorption coefficient, photo conductivity, reflectivity, and loss function） are calculated for the first time. The study of dielectric constant （ε1） indicates the Drude-like behavior. The absorption and conductivity spectra suggest that the compound is metallic. The reflectance spectrum shows that this compound has the potential to be used as a solar reflector. The thermodynamic properties such as the temperature and pressure dependent bulk modulus, Debye temperature, specific heats, and thermal expansion coefficient of Mo2Ga2C MAX phase are derived from the quasi-harmonic Debye model with phononic effect also for the first time. Analysis of Tc expression using available parameter values （DOS, Debye temperature, atomic mass, etc.） suggests that the compound is less likely to be superconductor.
基金financially supported by the National Natural Science Foundation of China (No.51771044)the Natural Science Foundation of Hebei Province (No.E2019501061)+2 种基金the Fundamental Research Funds for the Central Universities (No. N2023027)Program of Introducing Talents of Discipline Innovation to Universities 2.0 (No.BP0719037)LiaoNing Revitalization Talents Program (No.XLYC1802023)
文摘In this work,the effects of Co doping on the magnetostructural coupling transformation of Ni_(50-x)Co_(x)Mn_(50-y)Ti_(y)(x=0-15,y=12.5-15)Heusler alloys were systematically investigated through the first-princi-ples calculations and experimental verification.The cal-culation result indicates that the doped Co atoms prefer to occupy the Ni sublattice.The Co atoms tend to flock together in terms of the lowest energy principle.Since the formation energy of the austenite is higher than that of the martensite,the alloys will undergo martensitic transfor-mation for the Ni_(50-x)Co_(x)Mn_(37.5)Ti_(12.5)alloys(x=0-12.5).The magnetostructural coupling point of Ni_(50-x)Co_(x)Mn_(37.5)Ti_(12.5)alloys is predicted in the vicinity of x=11-12.Based on the computational composition Ni_(37.5)Co_(12.5)Mn_(37.5)Ti_(12.5),the Ni_(36)Co_(14)Mn_(36)Ti_(14)alloy with magnetostructural coupling near room temperature was experimentally developed by simultaneously increasing the Ti and Co contents.The largest magnetization change(ΔM)and magnetic entropy changes(ΔS_(m))obtained under magnetic field of 5 T for the martensitic transformation in the Ni_(36)Co_(14)Mn_(36)Ti_(14) alloy are about 87.6 A·m^(2)·kg^(-1)and 21 J·kg^(-1)·K^(-1),respectively.The fracture strength and strain for non-textured polycrystalline Ni_(36)Co_(14)Mn_(36)Ti_(14)alloy reach 953 MPa and 12.3%,respectively.The results show that the alloy not only possesses a large magne-tocaloric effect but also has excellent mechanical proper-ties.In addition,the 6 M modulated martensite is evidenced in the Ni-Co-Mn-Ti alloys via transmission electron microscopy technique.
