The adsorptive denitrification performance of MIL-101(Cr)-0.5 toward pyridine,aniline or quinoline in simulated fuels with basic nitrogen content of 1732μg/g was evaluated separately.Furthermore,the effects of adsorp...The adsorptive denitrification performance of MIL-101(Cr)-0.5 toward pyridine,aniline or quinoline in simulated fuels with basic nitrogen content of 1732μg/g was evaluated separately.Furthermore,the effects of adsorption temperature,adsorption time and adsorbent dosage on their adsorptive denitrification performance were systematically investigated.The experimental results demonstrated that under a fixed adsorbent dosage of 0.05 g and a simulated fuel volume of 10 mL,the optimal removal efficiency for aniline was achieved at 30℃ within 30 min,whereas higher temperatures and longer times(40℃and 40 min)were required for effective removal of pyridine and quinoline.Density Functional Theory(DFT)calculations were conducted via Materials Studio(MS)software to study the adsorptive denitrification mechanism of MIL-101(Cr)toward these three basic nitrogen-containing compounds.The simulation calculation results revealed that the interaction between pyridine and MIL-101(Cr)primarily involved coordination adsorption.In contrast,the interaction between aniline or quinoline and MIL-101(Cr)proceeded mainly through coordination,with additional contributions fromπ-complexation and hydrogen bonding.The overall adsorption strength order is pyridine>aniline>quinoline.During the adsorption process,pyridine and quinoline transfer electrons to the MIL-101(Cr)surface through the H→C→N→Cr^(3+)pathway,while aniline transfers electrons to the MIL-101(Cr)surface through various pathways,including N→Cr^(3+),N→C→Cr^(3+)and N→H→O.Furthermore,adsorption kinetics studies indicated that the adsorption processes for all three basic nitrogen-containing compounds followed the quasi second order kinetic models.The experimental results on the effect of benzene on the adsorptive denitrification performance of MIL-101(Cr)-0.5 demonstrated that benzene exerted a more significant impact on the adsorption of aniline and quinoline.Finally,the adsorbent was regenerated using ethanol washing.It was found that MIL-101(Cr)-0.5 retained stable denitrification performance after two regeneration cycles.展开更多
The electric double layer(EDL)at the electrochemical interface is crucial for ion transport,charge transfer,and surface reactions in aqueous rechargeable zinc batteries(ARZBs).However,Zn anodes routinely encounter per...The electric double layer(EDL)at the electrochemical interface is crucial for ion transport,charge transfer,and surface reactions in aqueous rechargeable zinc batteries(ARZBs).However,Zn anodes routinely encounter persistent dendrite growth and parasitic reactions,driven by the inhomogeneous charge distribution and water-dominated environment within the EDL.Compounding this,classical EDL theory,rooted in meanfield approximations,further fails to resolve molecular-scale interfacial dynamics under battery-operating conditions,limiting mechanistic insights.Herein,we established a multiscale theoretical calculation framework from single molecular characteristics to interfacial ion distribution,revealing the EDL’s structure and interactions between different ions and molecules,which helps us understand the parasitic processes in depth.Simulations demonstrate that water dipole and sulfate ion adsorption at the inner Helmholtz plane drives severe hydrogen evolution and by-product formation.Guided by these insights,we engineered a“water-poor and anion-expelled”EDL using 4,1’,6’-trichlorogalactosucrose(TGS)as an electrolyte additive.As a result,Zn||Zn symmetric cells with TGS exhibited stable cycling for over 4700 h under a current density of 1 mA cm^(−2),while NaV_(3)O_(8)·1.5H_(2)O-based full cells kept 90.4%of the initial specific capacity after 800 cycles at 5 A g^(−1).This work highlights the power of multiscale theoretical frameworks to unravel EDL complexities and guide high-performance ARZB design through integrated theory-experiment approaches.展开更多
Underwater gas-liquid two-phase propulsion technology is an emerging propulsion method that offers high efficiency and unrestricted navigation speed.The integration of this technology into water ramjet engines can sig...Underwater gas-liquid two-phase propulsion technology is an emerging propulsion method that offers high efficiency and unrestricted navigation speed.The integration of this technology into water ramjet engines can significantly enhance propulsion efficiency and holds substantial potential for broad applications.However,forming a gas-liquid two-phase flow within the nozzle requires introducing a large amount of rammed seawater.At this time,there is a complex phase transition problem of combustion products in the combustion chamber,which makes the thermodynamic calculation for gas-liquid two-phase water ramjet engines particularly challenging.This paper proposes a thermodynamic calculation method for gas-liquid two-phase water ramjet engines,based on the energy equation for gas-liquid two-phase flow and traditional thermodynamic principles,enabling thermodynamic calculations under conditions of ultra-high water-fuel ratios.Additionally,ground ignition tests of the gas-liquid two-phase engine were conducted,yielding critical engine test parameters.The results demonstrate that the gas-liquid two-phase water ramjet engine achieves a high specific impulse,with a theoretical maximum specific impulse of up to 7000(N s)/kg.The multiphase flow effects significantly impact engine performance,with specific impulse losses reaching up to 25.86%.The error between the thrust and specific impulse in the ground test and the theoretical values is within 10%,validating the proposed thermodynamic calculation method as a reliable reference for further research on gas-liquid two-phase water ramjet engines.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
The vacuum reactive wetting and brazing of Er_(2)Si_(2)O_(7)/MoSi_(2) coatings were investigated using a (CoFeNiCrMn)_(88)Nb_(12) high-entropy alloy (HEA) brazing filler. The microstructural evolution and wettability ...The vacuum reactive wetting and brazing of Er_(2)Si_(2)O_(7)/MoSi_(2) coatings were investigated using a (CoFeNiCrMn)_(88)Nb_(12) high-entropy alloy (HEA) brazing filler. The microstructural evolution and wettability of the HEA filler were analyzed, with particular attention to the surface energy, interfacial stability, and electronic properties of the HEA filler/rare earth silicate coating system, as determined by density functional theory (DFT). As Nb diffused into the interface and the ErNbO_(4) phase formed, the wetting angle gradually decreased to 23.12° The effective wetting and spreading of the HEA brazing filler on the rare earth silicate coating surface are strongly correlated with the formation of the ErNbO_(4) phase at the interface. Furthermore, DFT calculations reveal that the interfacial bonding energy between the BCC' and FCC' phases and the ErNbO_(4) phase, after the wetting reaction, is significantly higher than the bonding energy between the initial filler and Er_(2)Si_(2)O_(7). This finding suggests that the formation of the ErNbO_(4) phase improves the wetting and spreading behavior of the filler.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
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
Ni-Mn-Ti Heusler alloys have great potential for elastocaloric refrigeration due to the colossal caloric effect and good mechanical properties. However, theoretical calculations on the characterization of the elastoca...Ni-Mn-Ti Heusler alloys have great potential for elastocaloric refrigeration due to the colossal caloric effect and good mechanical properties. However, theoretical calculations on the characterization of the elastocaloric effect are rare. An important parameter to evaluate the elastocaloric effect is the transformation entropy change, whose main source is the vibrational entropy change (ΔS_(vib)). Unfortunately, the widely used quasiharmonic approximation method fails in the prediction of the vibrational entropy for high-temperature austenite due to its dynamical instability at 0 K. To solve this problem, the temperature dependent effective potential method was used considering the temperature and anharmonic effect. Sc, V, and Zr doping at the Ti sites in B2 disordered Ni_(8)Mn_(5)Ti_(3) were studied about phase stability, martensitic transformation, and elastocaloric properties. The results revealed the austenitic structures of all the doping systems exhibit antiferromagnetic coupling characteristics at 300 K due to the temperature effect. Sc and Zr doping at the Ti sites decreased the ΔS_(vib) value, whereas V doping at the Ti site increased the ΔS_(vib) value. Further analysis proved the important evaluation criterion that the ΔS_(vib) value increases with the tetragonal distortion ratio and volume change, which has important guiding significance for improving the elastocaloric effect. Besides, the calculations of elastic constants presented all the doping systems maintain outstanding ductility evaluated from the B/G ratio. This work provides an effective strategy for designing excellent elastocaloric material with large vibrational entropy change and good mechanical properties.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
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
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
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 Ag_(2)Al 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℃,Ag_(2)O and AgAlO_(2) become unstable.The overall reaction pathway is solid solution→Ag_(2)Al→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
The first-principle calculations are performed to investigate the structural,mechanical and electronic properties of titanium borides （Ti2B,TiB and TiB2）.Those calculated lattice parameters are in good agreement wit...The first-principle calculations are performed to investigate the structural,mechanical and electronic properties of titanium borides （Ti2B,TiB and TiB2）.Those calculated lattice parameters are in good agreement with the experimental data and previous theoretical values.All these borides are found to be mechanically stable at ambient pressure.Compared with parent metal Ti （120 GPa）,the larger bulk modulus of these borides increase successively with the increase of the boron content in three borides,which may be due to direction bonding introduced by the boron atoms in the lattice and the strong covalent Ti-B bonds.Additionally,TiB can be regarded as a candidate of incompressible and hard material besides TiB2.Furthermore,the elastic anisotropy and Debye temperatures are also discussed by investigating the elastic constants and moduli.Electronic density of states and atomic Mulliken charges analysis show that chemical bonding in these titanium borides is a complex mixture of covalent,ionic,and metallic characters.展开更多
The structural stability, electronic and elastic properties of Pd3-xRhxV alloys with L12 and D022 structures were investigated theoretically by the first-principles calculations. The results reveal that with the incre...The structural stability, electronic and elastic properties of Pd3-xRhxV alloys with L12 and D022 structures were investigated theoretically by the first-principles calculations. The results reveal that with the increase of Rh content, the unit cell volume of Pd3-xRhxV alloys with L12 and D022 structures decreases, and the structure of Pd3-xRhxV alloys tends to transform from D022 to L12. The elastic parameters such as elastic constants, bulk modulus, shear modulus, elastic modulus, and Poisson ratio, were calculated and discussed in details. Electronic structures were also computed to reveal the underlying mechanism for the stability and elastic properties.展开更多
The physical characters and electrochemical properties of various phases in a Sn-Zn electrode, such as formation energy, plateau potential, specific capacity, as well as volume expansion, were calculated by the first-...The physical characters and electrochemical properties of various phases in a Sn-Zn electrode, such as formation energy, plateau potential, specific capacity, as well as volume expansion, were calculated by the first-principles plane-wave pseudo-potential method based on the den- sity functional theory. Sn-Zn films were also deposited on copper foils by an electroless plating technique. The actual composition and chemical characters were explored by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, plasma atomic emission spectrometry （ICP）, and constant current charge/discharge measurements （CC）. The results show that separation phases with tin and zinc including a small quantity of Cu6Sn5 phase were obtained, the initial lithium insertion capacity of the Sn-Zn film was 661 mAh/g, and obvious potential pla- teaus of about 0.4 V and 0.7 V were displayed, which is in accordance with the results of theoretical calculations. The capacity of the Sn-Zn film decreased seriously with the increase of cycle number.展开更多
To understand deeply the structural, elastic and thermodynamic characteristics of AI2X （X= Sc, Y） compounds in C15 type （space number 227） Cu2Mg structure, we have performed ab-initio density functional theory wit...To understand deeply the structural, elastic and thermodynamic characteristics of AI2X （X= Sc, Y） compounds in C15 type （space number 227） Cu2Mg structure, we have performed ab-initio density functional theory within the local density approximation （LDA） and the generalized gradient approximation （GGA）. The thermodynamic properties of the considered structures are obtained through the quasi-harmonic Debye model. We have presented the results on the basic physical parameters, such as the lattice constant, bulk modu- lus, pressure derivative of bulk modulus, second-order elastic constants, Zener anisotropy factor, Poissongs ratio, Youngts modulus, and isotropic shear modulus. In order to gain further information, the pressure- and temperature-dependent behaviour of the volume, bulk modulus, thermal expansion coefficient, heat capacity, entropy, Debye temperature and Griineisen parameter were also evaluated over a pressure range of 0-20 GPa for Al2Sc and 0-17 GPa for Al2Y compound and a wide temperature range of 0-2000 K for both compounds. The obtained results were compared with the other reported values.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
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
Using first-principles calculations, we systematically study the dissociations of 02 molecules on different ultrathin Pb（lll） films. According to our previous work revealing the molecular adsorption precursor states...Using first-principles calculations, we systematically study the dissociations of 02 molecules on different ultrathin Pb（lll） films. According to our previous work revealing the molecular adsorption precursor states for O2, we further explore why there are two nearly degenerate adsorption states on Pb（lll） ultrathin films, but no precursor adsorption states existing at all on Mg（0001） and Al（lll） surfaces. The reason is concluded to be the different surface electronic structures. For the O2 dissociation, we consider both the reaction channels from gas-like and molecularly adsorbed O2 molecules. We find that the energy barrier for O2 dissociation from the molecular adsorption precursor states is always smaller than that from O2 gas. The most energetically favorable dissociation process is found to be the same on different Pb（lll） fihns, and the energy barriers are found to be influenced by the quantum size effects of Pb（lll） films.展开更多
To investigate the origin of the strong dependence of martensitic transformation temperature on composition, the elastic properties of high temperature B2 phases of both NiTi and NiAI were calculated by a first-princi...To investigate the origin of the strong dependence of martensitic transformation temperature on composition, the elastic properties of high temperature B2 phases of both NiTi and NiAI were calculated by a first-principle method, the exact-muffin orbital method within coherent potential approximation. In the composition range of 50-56 at. pct Ni of NiTi and 60-70 at. pct Ni of NiAI in which martensitic transformation occurs, non-basalplane shear modulus c44 increases with increasing Ni content, while basal-plane shear modulus c＇ decreases. In the above composition ranges however the transformation temperature of NiAI increases with increasing Ni content while that of NiTi decreases from experimental observation. The softening of c＇ is experimentally observed only in NiAI, and the decrease of c＇ with increasing Ni content is responsible for the increase of transformation temperature. The result of the present work demonstrates that, besides c＇, c44 also influences the martensitic transformation of NiTi and plays quite important a role.展开更多
基金Supported by Basic Scientific Research Project of the Liaoning Provincial Department of Education Has Been Unveiled to Facilitate Local Project Funding (JYTMS20230835)Enhanced Scientific Research Project Funded by the Departmentof Higher Education in Liaoning Province (General program)(JYTMS20230852)。
文摘The adsorptive denitrification performance of MIL-101(Cr)-0.5 toward pyridine,aniline or quinoline in simulated fuels with basic nitrogen content of 1732μg/g was evaluated separately.Furthermore,the effects of adsorption temperature,adsorption time and adsorbent dosage on their adsorptive denitrification performance were systematically investigated.The experimental results demonstrated that under a fixed adsorbent dosage of 0.05 g and a simulated fuel volume of 10 mL,the optimal removal efficiency for aniline was achieved at 30℃ within 30 min,whereas higher temperatures and longer times(40℃and 40 min)were required for effective removal of pyridine and quinoline.Density Functional Theory(DFT)calculations were conducted via Materials Studio(MS)software to study the adsorptive denitrification mechanism of MIL-101(Cr)toward these three basic nitrogen-containing compounds.The simulation calculation results revealed that the interaction between pyridine and MIL-101(Cr)primarily involved coordination adsorption.In contrast,the interaction between aniline or quinoline and MIL-101(Cr)proceeded mainly through coordination,with additional contributions fromπ-complexation and hydrogen bonding.The overall adsorption strength order is pyridine>aniline>quinoline.During the adsorption process,pyridine and quinoline transfer electrons to the MIL-101(Cr)surface through the H→C→N→Cr^(3+)pathway,while aniline transfers electrons to the MIL-101(Cr)surface through various pathways,including N→Cr^(3+),N→C→Cr^(3+)and N→H→O.Furthermore,adsorption kinetics studies indicated that the adsorption processes for all three basic nitrogen-containing compounds followed the quasi second order kinetic models.The experimental results on the effect of benzene on the adsorptive denitrification performance of MIL-101(Cr)-0.5 demonstrated that benzene exerted a more significant impact on the adsorption of aniline and quinoline.Finally,the adsorbent was regenerated using ethanol washing.It was found that MIL-101(Cr)-0.5 retained stable denitrification performance after two regeneration cycles.
基金supported by the National Natural Science Foundation of China(52471240)the Natural Science Foundation of Zhejiang Province(LZ23B030003)+2 种基金the Fundamental Research Funds for the Central Universities(226-2024-00075)support from the Engineering and Physical Sciences Research Council(EPSRC,UK)RiR grant-RIR18221018-1EU COST CA23155。
文摘The electric double layer(EDL)at the electrochemical interface is crucial for ion transport,charge transfer,and surface reactions in aqueous rechargeable zinc batteries(ARZBs).However,Zn anodes routinely encounter persistent dendrite growth and parasitic reactions,driven by the inhomogeneous charge distribution and water-dominated environment within the EDL.Compounding this,classical EDL theory,rooted in meanfield approximations,further fails to resolve molecular-scale interfacial dynamics under battery-operating conditions,limiting mechanistic insights.Herein,we established a multiscale theoretical calculation framework from single molecular characteristics to interfacial ion distribution,revealing the EDL’s structure and interactions between different ions and molecules,which helps us understand the parasitic processes in depth.Simulations demonstrate that water dipole and sulfate ion adsorption at the inner Helmholtz plane drives severe hydrogen evolution and by-product formation.Guided by these insights,we engineered a“water-poor and anion-expelled”EDL using 4,1’,6’-trichlorogalactosucrose(TGS)as an electrolyte additive.As a result,Zn||Zn symmetric cells with TGS exhibited stable cycling for over 4700 h under a current density of 1 mA cm^(−2),while NaV_(3)O_(8)·1.5H_(2)O-based full cells kept 90.4%of the initial specific capacity after 800 cycles at 5 A g^(−1).This work highlights the power of multiscale theoretical frameworks to unravel EDL complexities and guide high-performance ARZB design through integrated theory-experiment approaches.
基金supported by the Stable Support Fund forBasic Disciplines,China(No.3072024WD0201)。
文摘Underwater gas-liquid two-phase propulsion technology is an emerging propulsion method that offers high efficiency and unrestricted navigation speed.The integration of this technology into water ramjet engines can significantly enhance propulsion efficiency and holds substantial potential for broad applications.However,forming a gas-liquid two-phase flow within the nozzle requires introducing a large amount of rammed seawater.At this time,there is a complex phase transition problem of combustion products in the combustion chamber,which makes the thermodynamic calculation for gas-liquid two-phase water ramjet engines particularly challenging.This paper proposes a thermodynamic calculation method for gas-liquid two-phase water ramjet engines,based on the energy equation for gas-liquid two-phase flow and traditional thermodynamic principles,enabling thermodynamic calculations under conditions of ultra-high water-fuel ratios.Additionally,ground ignition tests of the gas-liquid two-phase engine were conducted,yielding critical engine test parameters.The results demonstrate that the gas-liquid two-phase water ramjet engine achieves a high specific impulse,with a theoretical maximum specific impulse of up to 7000(N s)/kg.The multiphase flow effects significantly impact engine performance,with specific impulse losses reaching up to 25.86%.The error between the thrust and specific impulse in the ground test and the theoretical values is within 10%,validating the proposed thermodynamic calculation method as a reliable reference for further research on gas-liquid two-phase water ramjet engines.
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support from the National Natural Science Foundation of China(No.52374402)the National Key Research and Development Program(No.2022YFB3402200)+2 种基金the National Science and Technology Major Project(No.J2022-VII-0003-0045)the Project of Key areas of innovation team in Shaanxi Province(No.2024RS-CXTD-20)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(No.CX2024055).
文摘The vacuum reactive wetting and brazing of Er_(2)Si_(2)O_(7)/MoSi_(2) coatings were investigated using a (CoFeNiCrMn)_(88)Nb_(12) high-entropy alloy (HEA) brazing filler. The microstructural evolution and wettability of the HEA filler were analyzed, with particular attention to the surface energy, interfacial stability, and electronic properties of the HEA filler/rare earth silicate coating system, as determined by density functional theory (DFT). As Nb diffused into the interface and the ErNbO_(4) phase formed, the wetting angle gradually decreased to 23.12° The effective wetting and spreading of the HEA brazing filler on the rare earth silicate coating surface are strongly correlated with the formation of the ErNbO_(4) phase at the interface. Furthermore, DFT calculations reveal that the interfacial bonding energy between the BCC' and FCC' phases and the ErNbO_(4) phase, after the wetting reaction, is significantly higher than the bonding energy between the initial filler and Er_(2)Si_(2)O_(7). This finding suggests that the formation of the ErNbO_(4) phase improves the wetting and spreading behavior of the filler.
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 Foundation of China(Nos.52271172,and 51971085).
文摘Ni-Mn-Ti Heusler alloys have great potential for elastocaloric refrigeration due to the colossal caloric effect and good mechanical properties. However, theoretical calculations on the characterization of the elastocaloric effect are rare. An important parameter to evaluate the elastocaloric effect is the transformation entropy change, whose main source is the vibrational entropy change (ΔS_(vib)). Unfortunately, the widely used quasiharmonic approximation method fails in the prediction of the vibrational entropy for high-temperature austenite due to its dynamical instability at 0 K. To solve this problem, the temperature dependent effective potential method was used considering the temperature and anharmonic effect. Sc, V, and Zr doping at the Ti sites in B2 disordered Ni_(8)Mn_(5)Ti_(3) were studied about phase stability, martensitic transformation, and elastocaloric properties. The results revealed the austenitic structures of all the doping systems exhibit antiferromagnetic coupling characteristics at 300 K due to the temperature effect. Sc and Zr doping at the Ti sites decreased the ΔS_(vib) value, whereas V doping at the Ti site increased the ΔS_(vib) value. Further analysis proved the important evaluation criterion that the ΔS_(vib) value increases with the tetragonal distortion ratio and volume change, which has important guiding significance for improving the elastocaloric effect. Besides, the calculations of elastic constants presented all the doping systems maintain outstanding ductility evaluated from the B/G ratio. This work provides an effective strategy for designing excellent elastocaloric material with large vibrational entropy change and good mechanical properties.
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.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 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 Ag_(2)Al 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℃,Ag_(2)O and AgAlO_(2) become unstable.The overall reaction pathway is solid solution→Ag_(2)Al→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(2010JK404) supported by the Education Committee Natural Science Foundation of Shaanxi Province,ChinaProjects(ZK0918,ZK0915) supported by the Baoji University of Arts and Sciences Key Research,China
文摘The first-principle calculations are performed to investigate the structural,mechanical and electronic properties of titanium borides （Ti2B,TiB and TiB2）.Those calculated lattice parameters are in good agreement with the experimental data and previous theoretical values.All these borides are found to be mechanically stable at ambient pressure.Compared with parent metal Ti （120 GPa）,the larger bulk modulus of these borides increase successively with the increase of the boron content in three borides,which may be due to direction bonding introduced by the boron atoms in the lattice and the strong covalent Ti-B bonds.Additionally,TiB can be regarded as a candidate of incompressible and hard material besides TiB2.Furthermore,the elastic anisotropy and Debye temperatures are also discussed by investigating the elastic constants and moduli.Electronic density of states and atomic Mulliken charges analysis show that chemical bonding in these titanium borides is a complex mixture of covalent,ionic,and metallic characters.
基金Project (50861002) supported by the National Natural Science Foundation of ChinaProject (0991051) supported by the Natural Science Foundation of Guangxi Province, China+2 种基金Project (08JJ6001) supported by the Natural Science Foundation of Hunan Province, ChinaProject (KF0803) supported by Key Laboratory of Materials Design and Preparation Technology of Hunan Province, ChinaProject (X071117) supported by the Scientific Research Foundation of Guangxi University, China
文摘The structural stability, electronic and elastic properties of Pd3-xRhxV alloys with L12 and D022 structures were investigated theoretically by the first-principles calculations. The results reveal that with the increase of Rh content, the unit cell volume of Pd3-xRhxV alloys with L12 and D022 structures decreases, and the structure of Pd3-xRhxV alloys tends to transform from D022 to L12. The elastic parameters such as elastic constants, bulk modulus, shear modulus, elastic modulus, and Poisson ratio, were calculated and discussed in details. Electronic structures were also computed to reveal the underlying mechanism for the stability and elastic properties.
基金supported by the National Nature Science Foundation of China (No. 50771046)the Foundation from Department of Education of Guangdong Province (No. C10179)
文摘The physical characters and electrochemical properties of various phases in a Sn-Zn electrode, such as formation energy, plateau potential, specific capacity, as well as volume expansion, were calculated by the first-principles plane-wave pseudo-potential method based on the den- sity functional theory. Sn-Zn films were also deposited on copper foils by an electroless plating technique. The actual composition and chemical characters were explored by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, plasma atomic emission spectrometry （ICP）, and constant current charge/discharge measurements （CC）. The results show that separation phases with tin and zinc including a small quantity of Cu6Sn5 phase were obtained, the initial lithium insertion capacity of the Sn-Zn film was 661 mAh/g, and obvious potential pla- teaus of about 0.4 V and 0.7 V were displayed, which is in accordance with the results of theoretical calculations. The capacity of the Sn-Zn film decreased seriously with the increase of cycle number.
文摘To understand deeply the structural, elastic and thermodynamic characteristics of AI2X （X= Sc, Y） compounds in C15 type （space number 227） Cu2Mg structure, we have performed ab-initio density functional theory within the local density approximation （LDA） and the generalized gradient approximation （GGA）. The thermodynamic properties of the considered structures are obtained through the quasi-harmonic Debye model. We have presented the results on the basic physical parameters, such as the lattice constant, bulk modu- lus, pressure derivative of bulk modulus, second-order elastic constants, Zener anisotropy factor, Poissongs ratio, Youngts modulus, and isotropic shear modulus. In order to gain further information, the pressure- and temperature-dependent behaviour of the volume, bulk modulus, thermal expansion coefficient, heat capacity, entropy, Debye temperature and Griineisen parameter were also evaluated over a pressure range of 0-20 GPa for Al2Sc and 0-17 GPa for Al2Y compound and a wide temperature range of 0-2000 K for both compounds. The obtained results were compared with the other reported values.
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 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Project supported by the National Natural Science Foundation of China(Grant Nos.90921003,10904004 and 60776063)the Fundamental Research Funds for the Central Universities,China(Grant No.JD1109)
文摘Using first-principles calculations, we systematically study the dissociations of 02 molecules on different ultrathin Pb（lll） films. According to our previous work revealing the molecular adsorption precursor states for O2, we further explore why there are two nearly degenerate adsorption states on Pb（lll） ultrathin films, but no precursor adsorption states existing at all on Mg（0001） and Al（lll） surfaces. The reason is concluded to be the different surface electronic structures. For the O2 dissociation, we consider both the reaction channels from gas-like and molecularly adsorbed O2 molecules. We find that the energy barrier for O2 dissociation from the molecular adsorption precursor states is always smaller than that from O2 gas. The most energetically favorable dissociation process is found to be the same on different Pb（lll） fihns, and the energy barriers are found to be influenced by the quantum size effects of Pb（lll） films.
基金Part of the calculations in this work was performed ona Shenteng 6800 supercomputer at CNIC, China.
文摘To investigate the origin of the strong dependence of martensitic transformation temperature on composition, the elastic properties of high temperature B2 phases of both NiTi and NiAI were calculated by a first-principle method, the exact-muffin orbital method within coherent potential approximation. In the composition range of 50-56 at. pct Ni of NiTi and 60-70 at. pct Ni of NiAI in which martensitic transformation occurs, non-basalplane shear modulus c44 increases with increasing Ni content, while basal-plane shear modulus c＇ decreases. In the above composition ranges however the transformation temperature of NiAI increases with increasing Ni content while that of NiTi decreases from experimental observation. The softening of c＇ is experimentally observed only in NiAI, and the decrease of c＇ with increasing Ni content is responsible for the increase of transformation temperature. The result of the present work demonstrates that, besides c＇, c44 also influences the martensitic transformation of NiTi and plays quite important a role.
