By measuring the hardness of carburized layer of a new type supersaturated carburizing steel （35Cr3SiMnMoV） at different temper temperature for 2 h, the relationship curve between the carburized layer hardness and t...By measuring the hardness of carburized layer of a new type supersaturated carburizing steel （35Cr3SiMnMoV） at different temper temperature for 2 h, the relationship curve between the carburized layer hardness and the temper temperature is established. The result indicates that the hardness goes down firstly, then up and down, just like a wave consistent with the temperature increase. A secondary hardening peak appears at 570 ℃ or so. Based on Empirical Election Theory （EET） of Solids and Molecules, the valence electron structures （VESs） containing α-Fe-C, α-Fe-C-Me segregation structure units and carbide are calculated. The laws of temper process and hardness change with the temper temperature are explained, and the fact that reconstruction of θ-Fe3C is prior to that of special carbide at high tempering is analyzed with the phase structure formation factor, S, being taken into consideration. Therefore, the laws of temper process and hardness change of supersaturated carburized layer at different temper temperature can be traced back to valence electron structure （VES） level of alloy phase.展开更多
Formate is an important liquid chemical,which can be produced by electrocatalytic carbon dioxide reduction reaction(CO_(2)RR).Most of the metal catalysts for CO_(2)RR to formate are toxic or noble metals,such as Cd,Hg...Formate is an important liquid chemical,which can be produced by electrocatalytic carbon dioxide reduction reaction(CO_(2)RR).Most of the metal catalysts for CO_(2)RR to formate are toxic or noble metals,such as Cd,Hg,Pb and Pd,leading to the environmental pollution or increased production costs.Herein,we develop an environmentally friendly and low-cost NiZn alloy catalyst for CO_(2)RR to formate.The X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and transmission electron microscopy(TEM)confirm the alloy structure of the prepared NiZn catalyst.As for a catalyst for CO_(2)RR,the NiZn alloy exhibits the FE_(HCOO)^(-)(Faraday efficiency of HCOO^(-))of 36±0.7%at-0.9 V vs.RHE in 0.1 M KHCO_(3),and remarkable stability for 40,000 s at-0.8,-0.9,-1.0 and-1.1 V vs.RHE,respectively.Theoretical calculation results indicate that the NiZn alloy exhibits the middle valence electron structure between the Zn and Ni metal,resulting in the favorable pathway for HCOOH formation but unfavorable for the hydrogen evolution reaction and CO production.The Ultraviolet Photoelectron Spectroscopy results verify the modulated valence electron structure for NiZn alloy as compared to Ni and Zn,consistent with the theoretical calculation results.This work provides new insights into design of alloy catalysts for CO_(2)RR to formate.展开更多
Based on the empirical electronic theory of solids and molecules （EET）, the actual model for unit cell of cementite （0-FeaC） was built and the valence electron structures （VES） of cementite with specified site a...Based on the empirical electronic theory of solids and molecules （EET）, the actual model for unit cell of cementite （0-FeaC） was built and the valence electron structures （VES） of cementite with specified site and a number of Fe atoms substituted by alloying atoms of M （ M=Cr, V, W, Mo, Mn ） were computed by statistical method. By defining P as the stability factor, the stability of alloyed cementite with different numbers and sites of Fe atoms substituted by M was calculated. Calculation results show that the density of lattice electrons, the symmetry of distribution of covalent electron pairs and bond energy have huge influence on the stability of alloyed cementite. It is more stable as M substitutes for FeE than for Fe1. The alloyed cementite is the most stable when Cr, Mo, W and V substitute for 2 atoms of Fe2 at the sites of Nos. 2 and 3 （or No. 6 and No. 7）. The stability of alloyed cementite decreases gradually as being substitutional doped by W, Cr, V, Mo and Mn.展开更多
The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules （EET）. A criterion for the ionic conductivity was ...The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules （EET）. A criterion for the ionic conductivity was proposed, i.e. the 1/（nAnB） increases with increasing the ionic conductivity when x or y〈20% （in molar fraction）.展开更多
According to EET theory, the valence electron structures of RE in the solid solution of austenite, pearlite and martensite were calculated. The influence of RE in solid solution on phase transformation of pearlite and...According to EET theory, the valence electron structures of RE in the solid solution of austenite, pearlite and martensite were calculated. The influence of RE in solid solution on phase transformation of pearlite and recrystallization of martensite was explained by the valence electron structure data of phases. Calculating results indicate that C element is favorite to enhance the number of RE in the solid solution. RE in the solute solution shortens the incubation period of proeutectoid ferrite, increases its quantity and carbon content, decreases the quantity of pearlite and thickness of its lamellas and lamellar spacing, then the strength and hardness of pearlite are improved and granular pearlite can be obtained. RE dissolved in martensite intensifies martensite, enhances tempering stability of martensite, increases its recrystallization temperature and prolongs the holding time needed during tempering.展开更多
Intermetallic compounds REIn_(3)(RE=rare earth)have attracted much attention due to their unique characteristics:crystal field effect,Kondo effect,superconductivity,heavy fermion,and antiferromagnetism,and their cobal...Intermetallic compounds REIn_(3)(RE=rare earth)have attracted much attention due to their unique characteristics:crystal field effect,Kondo effect,superconductivity,heavy fermion,and antiferromagnetism,and their cobalt diluted alloys exhibit the ferromagnetic half-metallic characteristics at room temperature.In this study,an empirical electron theory(EET)is employed to investigate systemically the valence electronic structure,the thermal and magnetic properties of REX_(3) and their cobalt diluted alloys for revealing the mechanism of physical properties.The calculated bond length,melting point,and magnetic moment match the experimental ones very well.The study reveals that structural stability and physical properties of REX_(3) and their cobalt dilute alloys are strongly related to their valence electron structures.It is suggested that the structural stability and cohesive energy depend upon the covalent electron,the melting point is modulated by covalent electron pair,and the magnetic moment is originated from 3d magnetic electron.The ferromagnetic characteristics of Co-diluted REIn3 alloys is originated from the introduction of strong ferromagnetic Co atom,but,a competition is caused between the electron transition from valence electron to magnetic electron on d orbit and its reversal electron transformation with increasing the content of cobalt,which results in the formations of diluted magnetic Gd(In,Co)_(3) alloy with minor amount of cobalt and strong magnetic Nd(In,Co)_(3) alloy with doping more Co atoms.展开更多
By calculating the electron structures of the phases that phosphor, sulfur and alloying elements dissolving inγ-Fe, the reason why alloying elements can bring centerline segregation in continuous casting slab (CCS) w...By calculating the electron structures of the phases that phosphor, sulfur and alloying elements dissolving inγ-Fe, the reason why alloying elements can bring centerline segregation in continuous casting slab (CCS) with nA, the number of electrons on the strongest covalent bonds, and the structure formation factor S were investigated, and an electron structural criterion to control and to eliminate the centerline segregation was advanced. Basing on this, the electron structures of a part of rare earth phosphides and sulfides are calculated, the physical mechanism that rare earth elements can control the segregation of phosphor and sulfur is analyzed, and the criterion is well verified.展开更多
In the present study, two models of atom occupation in LaNi4Co were put forward and corresponding valence electron structures （VESs） of these two models were investigated according to empirical electron theory （EET...In the present study, two models of atom occupation in LaNi4Co were put forward and corresponding valence electron structures （VESs） of these two models were investigated according to empirical electron theory （EET） of solids and molecules. Results demonstrate that the VES-concerned hardness factor （FH） of LaNi4Co is lower than that of LaNi5, so LaNi4Co has lower hardness, higher plasticity and improved anti-pulverization ability. In the mean time, the difference of the equilibrium hydrogen pressure between LaNiaCo and LaNi5 was analyzed in the electronic level. The analysis shows that the strength of the weakest bond net in octahedron lattice interstices of LaNi4Co is much lower than that in LaNis; consequently, LaNi4Co＇s bond net easily deforms to accommodate hydrogen so that LaNi4Co has lower equilibrium hydrogen pressure in comparison with LaNis. The results can provide some theory guide on the design of hydrogen storage alloys.展开更多
Gaseous dibenzo-7-phosphanorbornadiene P-sulfide anions APS （A C14H10 or anthracene） were generated via electrospray ionization, and characterized by magnetic-bottle photoelec- tron spectroscopy, velocity-map imagi...Gaseous dibenzo-7-phosphanorbornadiene P-sulfide anions APS （A C14H10 or anthracene） were generated via electrospray ionization, and characterized by magnetic-bottle photoelec- tron spectroscopy, velocity-map imaging （VMI） photoelectron spectroscopy, and quantum chemical calculations. The electron affinity （EA） and spin-orbit （SO） splitting of the APS＂ radical are determined from the photoelectron spectra and Franck-Condon factor simulations to be EA （2.62-4-0.05） eV and SO splitting （43-4-7） meV. VMI photoelectron images show strong and sharp peaks near the detachment threshold with an identical electron kinetic energy （eKE） of 17.9 meV at three different detachment wavelengths, which are therefore assigned to autodetachment from dipole-bound anion states. The B3LYP/6-31＋＋G（d,p） calculations indicate APS has a dipole moment of 3.31 Debye, large enough to support a dipole-bound electron.展开更多
Vacancy defects,as fundamental disruptions in metallic lattices,play an important role in shaping the mechanical and electronic properties of aluminum crystals.However,the influence of vacancy position under coupled t...Vacancy defects,as fundamental disruptions in metallic lattices,play an important role in shaping the mechanical and electronic properties of aluminum crystals.However,the influence of vacancy position under coupled thermomechanical fields remains insufficiently understood.In this study,transmission and scanning electron microscopy were employed to observe dislocation structures and grain boundary heterogeneities in processed aluminum alloys,suggesting stress concentrations and microstructural inhomogeneities associated with vacancy accumulation.To complement these observations,first-principles calculations and molecular dynamics simulations were conducted for seven single-vacancy configurations in face-centered cubic aluminum.The stress response,total energy,density of states(DOS),and differential charge density were examined under varying compressive strain(ε=0–0.1)and temperature(0–600 K).The results indicate that face-centered vacancies tend to reduce mechanical strength and perturb electronic states near the Fermi level,whereas corner and edge vacancies appear to have weaker effects.Elevated temperatures may partially restore electronic uniformity through thermal excitation.Overall,these findings suggest that vacancy position exerts a critical but position-dependent influence on coupled structure-property relationships,offering theoretical insights and preliminary experimental support for defect-engineered aluminum alloy design.展开更多
The interdependence of electrical parameters has long inhibited the progress of bismuth telluride(Bi_(2)Te3),limiting its widespread application in thermoelectric cooling and power generation.This work investigates th...The interdependence of electrical parameters has long inhibited the progress of bismuth telluride(Bi_(2)Te3),limiting its widespread application in thermoelectric cooling and power generation.This work investigates the n-type Bi_(2)Te_(2.79)Se_(0.21)I_(0.004)(Bi_(2)(Te,Se)_(3),BTS)system with light Zn doping,revealing that Zn addition simultaneously enhances the Seebeck coefficient(S)and electrical conductivity(σ)through the modulation of defect composition and multi-level band regulation.The substitution of Zn atoms at Bi sites enhances S via bandgap(E_(g))widening,band flattening,and band splitting effects,contributing to a competitive power factor(PF)of∼60μW⋅cm^(−1)⋅K^(−2).Additionally,thermal conductivity is maintained at a low level,leading to an extraordinary figure-of-merit(ZT)value of∼1.3 at room temperature.Furthermore,the Bi_(2)Zn_(0.01)Te_(2.79)Se_(0.21)I_(0.004) system demonstrates impressive thermoelectric device performance,with a maximum cooling temperature difference(ΔT_(max))of∼70.0 K at 300 K,rising to∼78.0 K at 323 K and∼85.7 K at 343 K,as well as a maximum conversion efficiency(η_(max))of∼6.2%under aΔT of 200 K.This study clarifies the mechanism of Zn doping and presents a cost-effective strategy for enhancing the performance of n-type BTS thermoelectrics and their devices.展开更多
Classical computation of electronic properties in large-scale materials remains challenging.Quantum computation has the potential to offer advantages in memory footprint and computational scaling.However,general and v...Classical computation of electronic properties in large-scale materials remains challenging.Quantum computation has the potential to offer advantages in memory footprint and computational scaling.However,general and viable quantum algorithms for simulating large-scale materials are still limited.We propose and implement random-state quantum algorithms to calculate electronic-structure properties of real materials.Using a random state circuit on a small number of qubits,we employ real-time evolution with first-order Trotter decomposition and Hadamard test to obtain electronic density of states,and we develop a modified quantum phase estimation algorithm to calculate real-space local density of states via direct quantum measurements.Furthermore,we validate these algorithms by numerically computing the density of states and spatial distributions of electronic states in graphene,twisted bilayer graphene quasicrystals,and fractal lattices,covering system sizes from hundreds to thousands of atoms.Our results manifest that the random-state quantum algorithms provide a general and qubit-efficient route to scalable simulations of electronic properties in large-scale periodic and aperiodic materials.展开更多
Sodium superionic conductor(NASICON)-type materials are promising cathodes for sodium-ion batteries due to their stable multi-channel frameworks and exceptional ionic conductivity.Among them,Na_(3)V_2(PO_4)_(2)F_(3)(N...Sodium superionic conductor(NASICON)-type materials are promising cathodes for sodium-ion batteries due to their stable multi-channel frameworks and exceptional ionic conductivity.Among them,Na_(3)V_2(PO_4)_(2)F_(3)(NVPF)has attracted significant attention.However,the low electronic conductivity and phase impurities limit its sodium storage capability.Herein,we present a Fe and Mn dual-doped NVPF(FM-NVPF)cathode with improved phase purity,electronic conductivity,and electrochemical activities.Detailed ex-situ analyses and density functional theory calculations reveal that Fe and Mn dopants induce defect energy levels and modulate the electronic structure,resulting in a direct-to-indirect bandgap transition in NVPF,which in turn increases carrier concentration and lifetime,accelerates ionic/electronic transport,and improves structural stability.As a result,the FM-NVPF cathode delivers a high capacity of 126.6 mAh g^(-1)at 0.1 C(1 C=128 mAh g^(-1))and outstanding high-rate capability of 67.6 mAh g^(-1)at 50 C,corresponding to 1.2 min per charge.Furthermore,Na ion full cells assembled with the FM-NVPF cathodes and hard carbon anodes exhibit a high energy density of about 175 Wh kg^(-1)_(cathode+anode mass)and appealing cyclic stability.This work provides an efficient strategy for developing high-purity and high-performance NVPF cathode materials for advanced sodium-ion batteries.展开更多
Optimizing the oxygen reduction reaction(ORR)kinetics requires precise control of intermediate adsorption at active sites,which can be achieved through orbital engineering by regulating the electronic structure.This s...Optimizing the oxygen reduction reaction(ORR)kinetics requires precise control of intermediate adsorption at active sites,which can be achieved through orbital engineering by regulating the electronic structure.This study addresses the challenge by exploring how modulation of the 3d-orbital electronic structure of FeN_(4) active sites influences ORR electrocatalysis.To realize this,a catalyst composed of Fe_(3)C nanoparticles and FeN_(4) single atoms anchored on carbon black(Fe_(3)C-FeN_(4)/CB)was synthesized via a synergistic strategy of spatial confinement and atmosphere control.This unique heterostructure creates interfaces between Fe_(3)C and FeN_(4) that modulate the electronic configuration of the FeN_(4) center,transforming its geometry from square-planar to quasi-octahedral.Spectroscopic characterizations and theoretical calculations reveal that this orbital modulation results in a downward shift of the Fe dband center,altering the reaction pathway and lowering the energy barrier for ORR.Consequently,the Fe_(3)C-FeN_(4)/CB catalyst exhibits outstanding ORR activity,four-electron selectivity,excellent methanol tolerance,and remarkable electrochemical stability.When applied in a zinc-air battery,it achieves a peak power density of 178.4 mW cm^(-2)and superior cycling stability compared to commercial Pt/C catalysts.This work provides valuable insights into heterointerface-induced orbital modulation as a promising design principle for high-performance ORR electrocatalysts.展开更多
Point defect engineering endows catalysts with novel physical and chemical properties,elevating their electrocatalytic efficiency.The introduction of defects emerges as a promising strategy,effectively modifying the e...Point defect engineering endows catalysts with novel physical and chemical properties,elevating their electrocatalytic efficiency.The introduction of defects emerges as a promising strategy,effectively modifying the electronic structure of active sites.This optimization influences the adsorption energy of intermediates,thereby mitigating reaction energy barriers,altering paths,enhancing selectivity,and ultimately improving the catalytic efficiency of electrocatalysts.To elucidate the impact of defects on the electrocatalytic process,we comprehensively outline the roles of various point defects,their synthetic methodologies,and characterization techniques.Importantly,we consolidate insights into the relationship between point defects and catalytic activity for hydrogen/oxygen evolution and CO_(2)/O_(2)/N_(2) reduction reactions by integrating mechanisms from diverse reactions.This underscores the pivotal role of point defects in enhancing catalytic performance.At last,the principal challenges and prospects associated with point defects in current electrocatalysts are proposed,emphasizing their role in advancing the efficiency of electrochemical energy storage and conversion materials.展开更多
Polymeric perylene diimide(PDI)has been evidenced as a good candidate for photocatalytic water oxidation,yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration.Her...Polymeric perylene diimide(PDI)has been evidenced as a good candidate for photocatalytic water oxidation,yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration.Herein,with crystal and atomic structures of the self-assembled PDI revealed from the X-ray diffraction pattern,the electronic structure is theoretically illustrated by the first-principles density functional theory calculations,suggesting the suitable band structure and the direct electronic transition for efficient photocatalytic oxygen evolution over PDI.It is confirmed that the carbonyl O atoms on the conjugation structure serve as the active sites for oxygen evolution reaction by the crystal orbital Hamiltonian group analysis.The calculations of reaction free energy changes indicate that the oxygen evolution reaction should follow the reaction pathway of H_(2)O→^(*)OH→^(*)O→^(*)OOH→^(*)O_(2)with an overpotential of 0.81 V.Through an in-depth theoretical computational analysis in the atomic and electronic structures,the origin of photocatalytic oxygen evolution activity for PDI is well illustrated,which would help the rational design and modification of polymeric photocatalysts for efficient oxygen evolution.展开更多
The discovery of high-temperature superconductivity in bilayer nickelate La_(3)Ni_(2)O_(7)under high-pressure conditions has spurred extensive efforts to stabilize superconductivity at ambient pressure.Recently,the re...The discovery of high-temperature superconductivity in bilayer nickelate La_(3)Ni_(2)O_(7)under high-pressure conditions has spurred extensive efforts to stabilize superconductivity at ambient pressure.Recently,the realization of superconductivity in compressively strained La_(3)Ni_(2)O_(7)thin films grown on the SrLaAlO_(4)substrates,with a T_(c)exceeding 40 K,represents a significant step toward this goal.Here,we investigate the influence of film thickness and carrier doping on the electronic structure of La_(3)Ni_(2)O_(7)thin films,ranging from 0.5 to 3 unit cells,using first-principles calculations.For a 2 unit-cell film with an optimal doping concentration of 0.3 hole per formula unit(0.15 hole/Ni),the Ni-d_(z^(2))interlayer bonding state crosses the Fermi level,resulting in the formation ofγpockets at the Fermi surface.These findings align with angle-resolved photoemission spectroscopy experimental data.Our results provide theoretical validation for the recent experimental discovery of ambient-pressure superconductivity in La_(3)Ni_(2)O_(7)thin films and underscore the significant impact of film thickness and carrier doping on electronic property modulation.展开更多
We report a study on the electronic structure and chemical bonding of the PB and AsB diatomic molecules using high-resolution photoelectron imaging of cryogenically-cooled PB^(−)and AsB^(−)anions.The electron affiniti...We report a study on the electronic structure and chemical bonding of the PB and AsB diatomic molecules using high-resolution photoelectron imaging of cryogenically-cooled PB^(−)and AsB^(−)anions.The electron affinities of PB and AsB are measured to be 2.751(1)and 2.600(1)eV,respectively.The ground states of the PB^(−)and AsB−anions are determined to be ^(2)Σ^(+) with a σ^(1)π^(4) valence electron configuration.The ground states of neutral PB and AsB are found to be ^(3)Π_(2) with a σ^(1)π^(3) electron configuration.The spin-orbit excited states(^(3)Π_(1) and ^(3)Π_(0)),as well as two low-lying singlet excited states(^(1)Σ^(+)and ^(1)Π),are observed.Unusual spectroscopic characteristics are observed in the ^(3)Π_(2) ground state of AsB,probably due to state mixing with a higher-lying ^(1)Δ_(2) state.The current work provides extensive electronic and spectroscopic information for the PB and AsB molecules.展开更多
Thework presents the electronic structure computations and optical spectroscopy studies of half-Heusler ScNiBi and YNiBi compounds.Our first-principles computations of the electronic structures were based on density f...Thework presents the electronic structure computations and optical spectroscopy studies of half-Heusler ScNiBi and YNiBi compounds.Our first-principles computations of the electronic structures were based on density functional theory accounting for spin-orbit coupling.These compounds are computed to be semiconductors.The calculated gap values make ScNiBi and YNiBi valid for thermoelectric and optoelectronic applications and as selective filters.In ScNiBi and YNiBi,an intense peak at the energy of−2 eV is composed of theNi 3d states in the conduction band,and the valence band mostly contains these states with some contributions from the Bi 6p and Sc 3d or Y 4d electronic states.These states participate in the formation of the indirect gap of 0.16 eV(ScNiBi)and 0.18 eV(YNiBi).Within the spectral ellipsometry technique in the interval 0.22–15μm of wavelength,the optical functions of materials are studied,and their dispersion features are revealed.A good matching of the experimental and modeled optical conductivity spectra allowed us to analyze orbital contributions.The abnormally low optical absorption observed in the low-energy region of the spectrum is referred to as the results of band calculations indicating a small density of electronic states near the Fermi energy of these complex materials.展开更多
Fabricating a durable electrocatalyst with performance comparable to noble metals for the alkaline hydrogen evolution reaction(HER)remains a significant challenge.In this work,we introduce a highly efficient and robus...Fabricating a durable electrocatalyst with performance comparable to noble metals for the alkaline hydrogen evolution reaction(HER)remains a significant challenge.In this work,we introduce a highly efficient and robust electrocatalyst by incorporating rhenium(Re)atoms into CoS nanoflakes(Re-CoS)for alkaline HER.The incorporation of Re atoms into the CoS lattice enhances the hybridization of Co 3d and S 2p orbitals,resulting in an optimized electronic structure that accelerates water dissociation on Co sites and optimizes hydrogen adsorptiondesorption on S sites,thereby boosting the HER rate.The optimal Re-CoS catalyst demonstrates a low overpotential of 72 mV at 10 mA cm^(-2)in 1 M KOH,along with excellent long-term stability,maintaining its catalytic activity over 200 h without significant degradation.These results suggest that the incorporation of Re atoms into CoS effectively couples the water dissociation and hydrogen addesorption steps of alkaline HER,offering a promising strategy for the development of noble metal-like electrocatalysts.展开更多
基金Funded by the Science and Technology Foundation of Retuned Students Studying Abroad of Shanxi Province of China(No. 1995-26)
文摘By measuring the hardness of carburized layer of a new type supersaturated carburizing steel （35Cr3SiMnMoV） at different temper temperature for 2 h, the relationship curve between the carburized layer hardness and the temper temperature is established. The result indicates that the hardness goes down firstly, then up and down, just like a wave consistent with the temperature increase. A secondary hardening peak appears at 570 ℃ or so. Based on Empirical Election Theory （EET） of Solids and Molecules, the valence electron structures （VESs） containing α-Fe-C, α-Fe-C-Me segregation structure units and carbide are calculated. The laws of temper process and hardness change with the temper temperature are explained, and the fact that reconstruction of θ-Fe3C is prior to that of special carbide at high tempering is analyzed with the phase structure formation factor, S, being taken into consideration. Therefore, the laws of temper process and hardness change of supersaturated carburized layer at different temper temperature can be traced back to valence electron structure （VES） level of alloy phase.
基金Natural Science Foundation of China(21872174,22002189,U1932148)the International Science and Technology Cooperation Program(2017YFE0127800,2018YFE0203402)+5 种基金the Hunan Provincial Science and Technology Program(2017XK2026)the Hunan Province Key Field R&D Program(2020WK2002)the Hunan Provincial Natural Science Foundation of China(2020JJ2041,2020JJ5691)the Shenzhen Science and Technology Innovation Project(JCYJ20180307151313532)the Hunan Provincial Science and Technology Plan Project(2017TP1001)the Fundamental Research Funds for the Central Universities of Central South University。
文摘Formate is an important liquid chemical,which can be produced by electrocatalytic carbon dioxide reduction reaction(CO_(2)RR).Most of the metal catalysts for CO_(2)RR to formate are toxic or noble metals,such as Cd,Hg,Pb and Pd,leading to the environmental pollution or increased production costs.Herein,we develop an environmentally friendly and low-cost NiZn alloy catalyst for CO_(2)RR to formate.The X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and transmission electron microscopy(TEM)confirm the alloy structure of the prepared NiZn catalyst.As for a catalyst for CO_(2)RR,the NiZn alloy exhibits the FE_(HCOO)^(-)(Faraday efficiency of HCOO^(-))of 36±0.7%at-0.9 V vs.RHE in 0.1 M KHCO_(3),and remarkable stability for 40,000 s at-0.8,-0.9,-1.0 and-1.1 V vs.RHE,respectively.Theoretical calculation results indicate that the NiZn alloy exhibits the middle valence electron structure between the Zn and Ni metal,resulting in the favorable pathway for HCOOH formation but unfavorable for the hydrogen evolution reaction and CO production.The Ultraviolet Photoelectron Spectroscopy results verify the modulated valence electron structure for NiZn alloy as compared to Ni and Zn,consistent with the theoretical calculation results.This work provides new insights into design of alloy catalysts for CO_(2)RR to formate.
基金Project(2014CFB801)supported by Natural Science Foundation of Hubei Province of ChinaProject(11304236)supported by the National Natural Science Foundation of China
文摘Based on the empirical electronic theory of solids and molecules （EET）, the actual model for unit cell of cementite （0-FeaC） was built and the valence electron structures （VES） of cementite with specified site and a number of Fe atoms substituted by alloying atoms of M （ M=Cr, V, W, Mo, Mn ） were computed by statistical method. By defining P as the stability factor, the stability of alloyed cementite with different numbers and sites of Fe atoms substituted by M was calculated. Calculation results show that the density of lattice electrons, the symmetry of distribution of covalent electron pairs and bond energy have huge influence on the stability of alloyed cementite. It is more stable as M substitutes for FeE than for Fe1. The alloyed cementite is the most stable when Cr, Mo, W and V substitute for 2 atoms of Fe2 at the sites of Nos. 2 and 3 （or No. 6 and No. 7）. The stability of alloyed cementite decreases gradually as being substitutional doped by W, Cr, V, Mo and Mn.
文摘The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules （EET）. A criterion for the ionic conductivity was proposed, i.e. the 1/（nAnB） increases with increasing the ionic conductivity when x or y〈20% （in molar fraction）.
文摘According to EET theory, the valence electron structures of RE in the solid solution of austenite, pearlite and martensite were calculated. The influence of RE in solid solution on phase transformation of pearlite and recrystallization of martensite was explained by the valence electron structure data of phases. Calculating results indicate that C element is favorite to enhance the number of RE in the solid solution. RE in the solute solution shortens the incubation period of proeutectoid ferrite, increases its quantity and carbon content, decreases the quantity of pearlite and thickness of its lamellas and lamellar spacing, then the strength and hardness of pearlite are improved and granular pearlite can be obtained. RE dissolved in martensite intensifies martensite, enhances tempering stability of martensite, increases its recrystallization temperature and prolongs the holding time needed during tempering.
文摘Intermetallic compounds REIn_(3)(RE=rare earth)have attracted much attention due to their unique characteristics:crystal field effect,Kondo effect,superconductivity,heavy fermion,and antiferromagnetism,and their cobalt diluted alloys exhibit the ferromagnetic half-metallic characteristics at room temperature.In this study,an empirical electron theory(EET)is employed to investigate systemically the valence electronic structure,the thermal and magnetic properties of REX_(3) and their cobalt diluted alloys for revealing the mechanism of physical properties.The calculated bond length,melting point,and magnetic moment match the experimental ones very well.The study reveals that structural stability and physical properties of REX_(3) and their cobalt dilute alloys are strongly related to their valence electron structures.It is suggested that the structural stability and cohesive energy depend upon the covalent electron,the melting point is modulated by covalent electron pair,and the magnetic moment is originated from 3d magnetic electron.The ferromagnetic characteristics of Co-diluted REIn3 alloys is originated from the introduction of strong ferromagnetic Co atom,but,a competition is caused between the electron transition from valence electron to magnetic electron on d orbit and its reversal electron transformation with increasing the content of cobalt,which results in the formations of diluted magnetic Gd(In,Co)_(3) alloy with minor amount of cobalt and strong magnetic Nd(In,Co)_(3) alloy with doping more Co atoms.
基金the Natural Science Foundation of Liaoning under grant No.20022150 the National Natural Science Foundation of China under grant No.50271030.
文摘By calculating the electron structures of the phases that phosphor, sulfur and alloying elements dissolving inγ-Fe, the reason why alloying elements can bring centerline segregation in continuous casting slab (CCS) with nA, the number of electrons on the strongest covalent bonds, and the structure formation factor S were investigated, and an electron structural criterion to control and to eliminate the centerline segregation was advanced. Basing on this, the electron structures of a part of rare earth phosphides and sulfides are calculated, the physical mechanism that rare earth elements can control the segregation of phosphor and sulfur is analyzed, and the criterion is well verified.
基金financially supported by National Natural Science Foundations of China(Nos.51301149 and 50371059)
文摘In the present study, two models of atom occupation in LaNi4Co were put forward and corresponding valence electron structures （VESs） of these two models were investigated according to empirical electron theory （EET） of solids and molecules. Results demonstrate that the VES-concerned hardness factor （FH） of LaNi4Co is lower than that of LaNi5, so LaNi4Co has lower hardness, higher plasticity and improved anti-pulverization ability. In the mean time, the difference of the equilibrium hydrogen pressure between LaNiaCo and LaNi5 was analyzed in the electronic level. The analysis shows that the strength of the weakest bond net in octahedron lattice interstices of LaNi4Co is much lower than that in LaNis; consequently, LaNi4Co＇s bond net easily deforms to accommodate hydrogen so that LaNi4Co has lower equilibrium hydrogen pressure in comparison with LaNis. The results can provide some theory guide on the design of hydrogen storage alloys.
基金supported by the U.S.Department of Energy(DOE),Office of Science,Office of Basic EnergySciences,Division of Chemical Sciences,Geosciences and Biosciences,and was performed using EMSLa national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory,which is operated by Battelle Memorial Institute for the DOEsupported by the National Science Foundation under Grant(No.CHE-1664799)
文摘Gaseous dibenzo-7-phosphanorbornadiene P-sulfide anions APS （A C14H10 or anthracene） were generated via electrospray ionization, and characterized by magnetic-bottle photoelec- tron spectroscopy, velocity-map imaging （VMI） photoelectron spectroscopy, and quantum chemical calculations. The electron affinity （EA） and spin-orbit （SO） splitting of the APS＂ radical are determined from the photoelectron spectra and Franck-Condon factor simulations to be EA （2.62-4-0.05） eV and SO splitting （43-4-7） meV. VMI photoelectron images show strong and sharp peaks near the detachment threshold with an identical electron kinetic energy （eKE） of 17.9 meV at three different detachment wavelengths, which are therefore assigned to autodetachment from dipole-bound anion states. The B3LYP/6-31＋＋G（d,p） calculations indicate APS has a dipole moment of 3.31 Debye, large enough to support a dipole-bound electron.
基金supported by the Research Project on Strengthening the Construction of an Important Ecological Security Barrier in Northern China by Higher Education Institutions in the Inner Mongolia Autonomous Region(STAQZX202313)the Inner Mongolia Autonomous Region Education Science‘14th Five-Year Plan’2024 Annual Research Project(NGJGH2024635).
文摘Vacancy defects,as fundamental disruptions in metallic lattices,play an important role in shaping the mechanical and electronic properties of aluminum crystals.However,the influence of vacancy position under coupled thermomechanical fields remains insufficiently understood.In this study,transmission and scanning electron microscopy were employed to observe dislocation structures and grain boundary heterogeneities in processed aluminum alloys,suggesting stress concentrations and microstructural inhomogeneities associated with vacancy accumulation.To complement these observations,first-principles calculations and molecular dynamics simulations were conducted for seven single-vacancy configurations in face-centered cubic aluminum.The stress response,total energy,density of states(DOS),and differential charge density were examined under varying compressive strain(ε=0–0.1)and temperature(0–600 K).The results indicate that face-centered vacancies tend to reduce mechanical strength and perturb electronic states near the Fermi level,whereas corner and edge vacancies appear to have weaker effects.Elevated temperatures may partially restore electronic uniformity through thermal excitation.Overall,these findings suggest that vacancy position exerts a critical but position-dependent influence on coupled structure-property relationships,offering theoretical insights and preliminary experimental support for defect-engineered aluminum alloy design.
基金supported by the National Key Research and Development Program of China (Grant No.2024YFA1210400)the National Science Fund for Distinguished Young Scholars (Grant No.52525101)+3 种基金the National Natural Science Foundation of China (Grant Nos.52450001 and 22409014)the International Cooperation and Exchange of the National Natural Science Foundation of China (Grant No.52411540237)the Tencent Xplorer Prizethe support of the National High-Level Talent Special Support Programs—Young Talents。
文摘The interdependence of electrical parameters has long inhibited the progress of bismuth telluride(Bi_(2)Te3),limiting its widespread application in thermoelectric cooling and power generation.This work investigates the n-type Bi_(2)Te_(2.79)Se_(0.21)I_(0.004)(Bi_(2)(Te,Se)_(3),BTS)system with light Zn doping,revealing that Zn addition simultaneously enhances the Seebeck coefficient(S)and electrical conductivity(σ)through the modulation of defect composition and multi-level band regulation.The substitution of Zn atoms at Bi sites enhances S via bandgap(E_(g))widening,band flattening,and band splitting effects,contributing to a competitive power factor(PF)of∼60μW⋅cm^(−1)⋅K^(−2).Additionally,thermal conductivity is maintained at a low level,leading to an extraordinary figure-of-merit(ZT)value of∼1.3 at room temperature.Furthermore,the Bi_(2)Zn_(0.01)Te_(2.79)Se_(0.21)I_(0.004) system demonstrates impressive thermoelectric device performance,with a maximum cooling temperature difference(ΔT_(max))of∼70.0 K at 300 K,rising to∼78.0 K at 323 K and∼85.7 K at 343 K,as well as a maximum conversion efficiency(η_(max))of∼6.2%under aΔT of 200 K.This study clarifies the mechanism of Zn doping and presents a cost-effective strategy for enhancing the performance of n-type BTS thermoelectrics and their devices.
基金supported by the Major Project for the Integration of ScienceEducation and Industry (Grant No.2025ZDZX02)。
文摘Classical computation of electronic properties in large-scale materials remains challenging.Quantum computation has the potential to offer advantages in memory footprint and computational scaling.However,general and viable quantum algorithms for simulating large-scale materials are still limited.We propose and implement random-state quantum algorithms to calculate electronic-structure properties of real materials.Using a random state circuit on a small number of qubits,we employ real-time evolution with first-order Trotter decomposition and Hadamard test to obtain electronic density of states,and we develop a modified quantum phase estimation algorithm to calculate real-space local density of states via direct quantum measurements.Furthermore,we validate these algorithms by numerically computing the density of states and spatial distributions of electronic states in graphene,twisted bilayer graphene quasicrystals,and fractal lattices,covering system sizes from hundreds to thousands of atoms.Our results manifest that the random-state quantum algorithms provide a general and qubit-efficient route to scalable simulations of electronic properties in large-scale periodic and aperiodic materials.
基金supported by the Innovation and Technology Fund-Innovation and Technology Support Program(ITF-ITSP)(Project No.ITS/126/21)Research Talent Hub for ITF project(RTH-ITF)(Project No.K-45-35-ZWC6)from the Innovation and Technology Commission of Hong Kong SARResearch Institute for Advanced Manufacturing(RIAM)at The Hong Kong Polytechnic University(Project No.1-CD9C)。
文摘Sodium superionic conductor(NASICON)-type materials are promising cathodes for sodium-ion batteries due to their stable multi-channel frameworks and exceptional ionic conductivity.Among them,Na_(3)V_2(PO_4)_(2)F_(3)(NVPF)has attracted significant attention.However,the low electronic conductivity and phase impurities limit its sodium storage capability.Herein,we present a Fe and Mn dual-doped NVPF(FM-NVPF)cathode with improved phase purity,electronic conductivity,and electrochemical activities.Detailed ex-situ analyses and density functional theory calculations reveal that Fe and Mn dopants induce defect energy levels and modulate the electronic structure,resulting in a direct-to-indirect bandgap transition in NVPF,which in turn increases carrier concentration and lifetime,accelerates ionic/electronic transport,and improves structural stability.As a result,the FM-NVPF cathode delivers a high capacity of 126.6 mAh g^(-1)at 0.1 C(1 C=128 mAh g^(-1))and outstanding high-rate capability of 67.6 mAh g^(-1)at 50 C,corresponding to 1.2 min per charge.Furthermore,Na ion full cells assembled with the FM-NVPF cathodes and hard carbon anodes exhibit a high energy density of about 175 Wh kg^(-1)_(cathode+anode mass)and appealing cyclic stability.This work provides an efficient strategy for developing high-purity and high-performance NVPF cathode materials for advanced sodium-ion batteries.
基金supported by the National Natural Science Foundation of China(Grant Nos.22272105 and 22572118)Natural Science Foundation of Shanghai(Grant No.23ZR1423900)。
文摘Optimizing the oxygen reduction reaction(ORR)kinetics requires precise control of intermediate adsorption at active sites,which can be achieved through orbital engineering by regulating the electronic structure.This study addresses the challenge by exploring how modulation of the 3d-orbital electronic structure of FeN_(4) active sites influences ORR electrocatalysis.To realize this,a catalyst composed of Fe_(3)C nanoparticles and FeN_(4) single atoms anchored on carbon black(Fe_(3)C-FeN_(4)/CB)was synthesized via a synergistic strategy of spatial confinement and atmosphere control.This unique heterostructure creates interfaces between Fe_(3)C and FeN_(4) that modulate the electronic configuration of the FeN_(4) center,transforming its geometry from square-planar to quasi-octahedral.Spectroscopic characterizations and theoretical calculations reveal that this orbital modulation results in a downward shift of the Fe dband center,altering the reaction pathway and lowering the energy barrier for ORR.Consequently,the Fe_(3)C-FeN_(4)/CB catalyst exhibits outstanding ORR activity,four-electron selectivity,excellent methanol tolerance,and remarkable electrochemical stability.When applied in a zinc-air battery,it achieves a peak power density of 178.4 mW cm^(-2)and superior cycling stability compared to commercial Pt/C catalysts.This work provides valuable insights into heterointerface-induced orbital modulation as a promising design principle for high-performance ORR electrocatalysts.
基金supported by the National Natural Science Foundation of China(U21A20281)the Special Fund for Young Teachers from Zhengzhou University(JC23557030,JC23257011)+1 种基金the Key Research Projects of Higher Education Institutions of Henan Province(24A530009)the Project of Zhongyuan Critical Metals Laboratory(GJJSGFYQ202336).
文摘Point defect engineering endows catalysts with novel physical and chemical properties,elevating their electrocatalytic efficiency.The introduction of defects emerges as a promising strategy,effectively modifying the electronic structure of active sites.This optimization influences the adsorption energy of intermediates,thereby mitigating reaction energy barriers,altering paths,enhancing selectivity,and ultimately improving the catalytic efficiency of electrocatalysts.To elucidate the impact of defects on the electrocatalytic process,we comprehensively outline the roles of various point defects,their synthetic methodologies,and characterization techniques.Importantly,we consolidate insights into the relationship between point defects and catalytic activity for hydrogen/oxygen evolution and CO_(2)/O_(2)/N_(2) reduction reactions by integrating mechanisms from diverse reactions.This underscores the pivotal role of point defects in enhancing catalytic performance.At last,the principal challenges and prospects associated with point defects in current electrocatalysts are proposed,emphasizing their role in advancing the efficiency of electrochemical energy storage and conversion materials.
基金supported by National Natural Science Foundation of China(No.523B2070,No.52225606).
文摘Polymeric perylene diimide(PDI)has been evidenced as a good candidate for photocatalytic water oxidation,yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration.Herein,with crystal and atomic structures of the self-assembled PDI revealed from the X-ray diffraction pattern,the electronic structure is theoretically illustrated by the first-principles density functional theory calculations,suggesting the suitable band structure and the direct electronic transition for efficient photocatalytic oxygen evolution over PDI.It is confirmed that the carbonyl O atoms on the conjugation structure serve as the active sites for oxygen evolution reaction by the crystal orbital Hamiltonian group analysis.The calculations of reaction free energy changes indicate that the oxygen evolution reaction should follow the reaction pathway of H_(2)O→^(*)OH→^(*)O→^(*)OOH→^(*)O_(2)with an overpotential of 0.81 V.Through an in-depth theoretical computational analysis in the atomic and electronic structures,the origin of photocatalytic oxygen evolution activity for PDI is well illustrated,which would help the rational design and modification of polymeric photocatalysts for efficient oxygen evolution.
基金supported by the National Key R&D Program of China(Gran Nos.2022YFA1402304 and 2022YFA1402802)the National Natural Science Foundation of China(Grant Nos.12494591,12122405,12274169,and 92165204)+4 种基金Program for Science and Technology Innovation Team in Zhejiang(Grant No.2021R01004)Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)Guangdong Fundamental Research Center for Magnetoelectric Physics(2024B0303390001)Guangdong Provincial Quantum Science Strategic Initiative(Grant No.GDZX2401010)the Fundamental Research Funds for the Central Universities。
文摘The discovery of high-temperature superconductivity in bilayer nickelate La_(3)Ni_(2)O_(7)under high-pressure conditions has spurred extensive efforts to stabilize superconductivity at ambient pressure.Recently,the realization of superconductivity in compressively strained La_(3)Ni_(2)O_(7)thin films grown on the SrLaAlO_(4)substrates,with a T_(c)exceeding 40 K,represents a significant step toward this goal.Here,we investigate the influence of film thickness and carrier doping on the electronic structure of La_(3)Ni_(2)O_(7)thin films,ranging from 0.5 to 3 unit cells,using first-principles calculations.For a 2 unit-cell film with an optimal doping concentration of 0.3 hole per formula unit(0.15 hole/Ni),the Ni-d_(z^(2))interlayer bonding state crosses the Fermi level,resulting in the formation ofγpockets at the Fermi surface.These findings align with angle-resolved photoemission spectroscopy experimental data.Our results provide theoretical validation for the recent experimental discovery of ambient-pressure superconductivity in La_(3)Ni_(2)O_(7)thin films and underscore the significant impact of film thickness and carrier doping on electronic property modulation.
基金supported by the National Science Foundation (Grant No.CHE-2403841)。
文摘We report a study on the electronic structure and chemical bonding of the PB and AsB diatomic molecules using high-resolution photoelectron imaging of cryogenically-cooled PB^(−)and AsB^(−)anions.The electron affinities of PB and AsB are measured to be 2.751(1)and 2.600(1)eV,respectively.The ground states of the PB^(−)and AsB−anions are determined to be ^(2)Σ^(+) with a σ^(1)π^(4) valence electron configuration.The ground states of neutral PB and AsB are found to be ^(3)Π_(2) with a σ^(1)π^(3) electron configuration.The spin-orbit excited states(^(3)Π_(1) and ^(3)Π_(0)),as well as two low-lying singlet excited states(^(1)Σ^(+)and ^(1)Π),are observed.Unusual spectroscopic characteristics are observed in the ^(3)Π_(2) ground state of AsB,probably due to state mixing with a higher-lying ^(1)Δ_(2) state.The current work provides extensive electronic and spectroscopic information for the PB and AsB molecules.
文摘Thework presents the electronic structure computations and optical spectroscopy studies of half-Heusler ScNiBi and YNiBi compounds.Our first-principles computations of the electronic structures were based on density functional theory accounting for spin-orbit coupling.These compounds are computed to be semiconductors.The calculated gap values make ScNiBi and YNiBi valid for thermoelectric and optoelectronic applications and as selective filters.In ScNiBi and YNiBi,an intense peak at the energy of−2 eV is composed of theNi 3d states in the conduction band,and the valence band mostly contains these states with some contributions from the Bi 6p and Sc 3d or Y 4d electronic states.These states participate in the formation of the indirect gap of 0.16 eV(ScNiBi)and 0.18 eV(YNiBi).Within the spectral ellipsometry technique in the interval 0.22–15μm of wavelength,the optical functions of materials are studied,and their dispersion features are revealed.A good matching of the experimental and modeled optical conductivity spectra allowed us to analyze orbital contributions.The abnormally low optical absorption observed in the low-energy region of the spectrum is referred to as the results of band calculations indicating a small density of electronic states near the Fermi energy of these complex materials.
基金financially supported by the Institute for Basic Science of Korea(No.IBS-R011-D1)the National Research Foundation of Korea(NRF)(No.NRF-2022R1A2C2093415)+5 种基金the Korea Basic Science Institute(National Research Facilities and Equipment Center)grant funded by the Ministry of Education(No.2022R1A6C101A751)the National Natural Science Foundation of China(Nos.22209186 and 22479149)the Natural Science Foundation of Jiangxi Province(No.310306484080)the Key Research and Development Program of Jiangxi Province(Nos.20223BBG74004 and 20232BBG70003)the Youth Innovation Promotion Association,Chinese Academy of Sciences(No.2023343)the financial support from the National Research Foundation of Korea Grant funded by the Korean government(NRF-2021R1I1A1A01050068)
文摘Fabricating a durable electrocatalyst with performance comparable to noble metals for the alkaline hydrogen evolution reaction(HER)remains a significant challenge.In this work,we introduce a highly efficient and robust electrocatalyst by incorporating rhenium(Re)atoms into CoS nanoflakes(Re-CoS)for alkaline HER.The incorporation of Re atoms into the CoS lattice enhances the hybridization of Co 3d and S 2p orbitals,resulting in an optimized electronic structure that accelerates water dissociation on Co sites and optimizes hydrogen adsorptiondesorption on S sites,thereby boosting the HER rate.The optimal Re-CoS catalyst demonstrates a low overpotential of 72 mV at 10 mA cm^(-2)in 1 M KOH,along with excellent long-term stability,maintaining its catalytic activity over 200 h without significant degradation.These results suggest that the incorporation of Re atoms into CoS effectively couples the water dissociation and hydrogen addesorption steps of alkaline HER,offering a promising strategy for the development of noble metal-like electrocatalysts.
