It is found from textbooks and literature that there are three different statements for the third law of thermodynamics,i.e., the Nernst theorem, the unattainability statement of absolute zero temperature, and the hea...It is found from textbooks and literature that there are three different statements for the third law of thermodynamics,i.e., the Nernst theorem, the unattainability statement of absolute zero temperature, and the heat capacity statement. It is pointed out that such three statements correspond to three thermodynamic parameters, which are, respectively, the entropy,temperature, and heat capacity, and can be obtained by extrapolating the experimental results of different parameters at ultralow temperatures to absolute zero. It is expounded that because there is no need for additional assumptions in the derivation of the Nernst equation, the Nernst theorem should be renamed as the Nernst statement. Moreover, it is proved that both the Nernst statement and the heat capacity statement are mutually deducible and equivalent, while the unattainability of absolute zero temperature is only a corollary of the Nernst statement or the heat capacity statement so that it is unsuitably referred to as one statement of the third law of thermodynamics. The conclusion is that the Nernst statement and the heat capacity statement are two equivalent statements of the third law of thermodynamics.展开更多
The interplay between lattice geometry,band topology and electronic correlations in the newly discovered kagome compounds AV3Sb5(A=K,Rb,Cs) makes this family a novel playground to investigate emergent quantum phenomen...The interplay between lattice geometry,band topology and electronic correlations in the newly discovered kagome compounds AV3Sb5(A=K,Rb,Cs) makes this family a novel playground to investigate emergent quantum phenomena,such as unconventional superconductivity,chiral charge density wave and electronic nematicity.These exotic quantum phases naturally leave nontrivial fingerprints in transport properties of AV3Sb5,both in electrical and thermal channels,which are prominent probes to uncover the underlying mechanisms.In this brief review,we highlight the unusual electrical and thermal transport properties observed in the unconventional charge ordered state of A V3Sb5,including giant anomalous Hall,anomalous Nernst,ambipolar Nernst and anomalous thermal Hall effects.Connections of these anomalous transport properties to time-reversal symmetry breaking,topological and multiband fermiology,as well as electronic nematicity,are also discussed.Finally,a perspective together with challenges of this rapid growing field are given.展开更多
Valley Nernst effect is a newly proposed and experimentally confirmed effect,which could be used to design novel thermoelectric devices.We study the valley Nernst effect in(M+N)-layer twisted multilayer graphene syste...Valley Nernst effect is a newly proposed and experimentally confirmed effect,which could be used to design novel thermoelectric devices.We study the valley Nernst effect in(M+N)-layer twisted multilayer graphene systems by a simple low-energy effective model.It is found that the total valley Nernst coefficient(VNC)is three orders of magnitude larger than that in monolayer group-Ⅵdichalcogenides.The total VNC increases with the increase of layer numbers.It is shown that the total VNC exhibits a structure with three peaks as a function of the Fermi energy.We identify that the central peak is always negative stemming from the flat band.Two shoulder peaks are positively induced by the conduction and valence bands,respectively.These predicted features can be tested experimentally.The present work would shed more light on valley caloritronics.展开更多
Condensed matters with high ionic conductivities are crucial in various solid devices such as solid-state batteries. The conduction ischaracterized by the cooperative ionic motion associated with the high carrier dens...Condensed matters with high ionic conductivities are crucial in various solid devices such as solid-state batteries. The conduction ischaracterized by the cooperative ionic motion associated with the high carrier density. However, the high cost of computingcorrelated ionic conductivities has forced almost all ab initio molecular dynamics (MD) to rely on the Nernst–Einstein dilute-solutionapproximation, which ignores the cross-correlation effect. Here we develop a chemical color-diffusion nonequilibrium MD (CCD-NEMD) method, which enables to calculate the correlated conductivities with fewer sampling steps than the conventional MD. ThisCCD-NEMD is demonstrated to well evaluate the conductivities in the representative solid electrolyte bulk Li10GeP2S12 andLi_(7)La_(3)Zr_(2)O_(12). We also applied CCD-NEMD to the grain boundary of Li_(7)La_(3)Zr_(2)O_(12) and demonstrated its applicability for calculatinginterfacial local conductivities, which is essential for investigating grain boundaries and composite electrolytes. CCD-NEMD canprovide further accurate understanding of ionics with ionic correlations and promote developing solid devices.展开更多
Magnetism and spin-orbit coupling are two fundamental and interconnected properties of oxide materials,that can give rise to various topological transport phenomena,including anomalous Hall and anomalous Nernst effect...Magnetism and spin-orbit coupling are two fundamental and interconnected properties of oxide materials,that can give rise to various topological transport phenomena,including anomalous Hall and anomalous Nernst effects.These transport responses can be significantly enhanced by designing an electronic structure with a large Berry curvature.In this context,rocksalt-ordered double perovskites(DP),denoted as A2BB’O6,with two distinct transition metal sites are very powerful platforms for exploration and research.In this work,we present a comprehensive study based on the intrinsic anomalous transport in cubic and tetragonal stable DP compounds with 3d-4d/5d elements.Our findings reveal that certain DP compounds show a large anomalous Hall effect,displaying topological band crossings in the proximity of the Fermi energy.展开更多
Anomalous Nernst effect generates a transverse voltage perpendicular to the temperature gradient.It has several advantages compared with the longitudinal thermoelectricity for energy conversion,such as decoupling of e...Anomalous Nernst effect generates a transverse voltage perpendicular to the temperature gradient.It has several advantages compared with the longitudinal thermoelectricity for energy conversion,such as decoupling of electronic and thermal transports,higher flexibility,and simpler lateral structure.However,a design principle beyond specific materials systems for obtaining a large anomalous Nernst conductivity(ANC)is still absent.In this work,we theoretically demonstrate that a pair of Dirac nodes under a Zeeman field manifests an odd-distributed,double-peak anomalous Hall conductivity curve with respect to the chemical potential and a compensated carrier feature,leading to an enhanced ANC compared with that of a simple Weyl semimetal with two Weyl nodes.Based on first-principles calculations,we then provide two Dirac semimetal candidates,i.e.,Na3Bi and NaTeAu,and show that under a Zeeman field,they exhibit a sizable ANC value of 0.4 Am^(-1)K^(-1) and 1.3 Am^(-1)K^(-1),respectively,near the Fermi level.Such an approach is also applicable to ferromagnetic materials with intrinsic Zeeman splitting,as exemplified by a hypothetical alloy NaFeTe2Au2,exhibiting an ANC as high as 3.7 Am^(-1)K^(-1) at the Fermi level.Our work provides a design principle with a prototype band structure for enhanced ANC pinning at the Fermi level,shedding light on the inverse design of other specific functional materials based on electronic structure.展开更多
The unattainability of the absolute zero of temperature is proved by using Carnot’s theorem. Hence this unattainability is distinct from the Planck-Fer-mi statement of the Third Law of Thermodynamics that the entropy...The unattainability of the absolute zero of temperature is proved by using Carnot’s theorem. Hence this unattainability is distinct from the Planck-Fer-mi statement of the Third Law of Thermodynamics that the entropy vanishes at ?T=0. It is shown that the isothermal compressibility KT is in general larger than the adiabatic compressibility Ks and the difference KT?−?Ks?vanishes in the low temperature limit.展开更多
The interplay of magnetism and topology opens up the possibility for exotic linear response effects,such as the anomalous Hall effect and the anomalous Nernst effect,which can be strongly enhanced by designing a large...The interplay of magnetism and topology opens up the possibility for exotic linear response effects,such as the anomalous Hall effect and the anomalous Nernst effect,which can be strongly enhanced by designing a large Berry curvature in the electronic structure.Magnetic Heusler compounds are a promising class of materials for this purpose because they are versatile,show magnetism,and their electronic structure hosts strong topological features.Here,we provide a comprehensive study of the intrinsic anomalous transport for magnetic cubic full Heusler compounds and we illustrate that several Heusler compounds outperform the best so far reported materials.The results reveal the importance of symmetries,especially mirror planes,in combination with magnetism for giant anomalous Hall and Nernst effects,which should be valid in general for linear responses(spin Hall effect,spin orbital torque,etc.)dominated by intrinsic contributions.展开更多
A simple rational model is proposed for discharge of batteries with aqueous electrolytes, based on Nernst equation. Details of electrode kinetics are not taken into account. Only a few overall parameters of the batter...A simple rational model is proposed for discharge of batteries with aqueous electrolytes, based on Nernst equation. Details of electrode kinetics are not taken into account. Only a few overall parameters of the battery are considered. A simple algorithm, with variable time step-length <span style="font-family:Verdana;">Δ</span><i><span style="font-family:Verdana;">t</span></i><span style="font-family:Verdana;">, is presented, for proposed model. The model is first applied to Daniel cell, in order to clar</span><span style="font-family:Verdana;">ify</span><span style="font-family:""><span style="font-family:Verdana;"> concepts and principles of battery operation. It is found that initial pinching, in time-history curve of voltage </span><i><span style="font-family:Verdana;">E-t</span></i><span style="font-family:Verdana;">, is due to initial under-concentration of product ion. Then, model is applied </span></span><span style="font-family:Verdana;">to</span><span> a lead-acid battery. In absence of an ion product, and in order to construct nominator of Nernst ratio, such an ion, with coefficient tending to zero, is assumed, thus yielding unity in nominator. Time-history curves of voltage, for various values of internal resistance, are compared with corresponding published experimental curves. Temperature effect on voltage-time curve is examined. Proposed model can be extended to other types of batteries, which can be considered as having aqueous electrolytes, too.</span>展开更多
The maximum electrical efficiency of fuel cell system,ηemax, is important for the understanding and development of the fuel cell technology. Attempt is made to build a theory for ηemaxby considering the energy requi...The maximum electrical efficiency of fuel cell system,ηemax, is important for the understanding and development of the fuel cell technology. Attempt is made to build a theory for ηemaxby considering the energy requirement of heating the fuel and air streams to the fuel cell operating temperature T. A general thermodynamic analysis is performed and the energy balances for the overall operating processes of a fuel cell system are established. Explicit expressions for the determination of ηemax are deduced. Unlike the Carnot efficiency,ηemaxis found to be fuel specific. Except for hydrogen fuel, chemical equilibrium calculations are necessary to compute ηemax.Analytical solutions for the chemical equilibrium of alkane fuels are presented. The theoretical model is used to analyze the effects of T and the steam contents of CH4, C3 H8,and H2 on ηemax for systems with various degrees of waste heat recovery.Contrary to the common perception concerning methane and propane fuels, ηemax decreases substantially with the increase of T. Moreover, ηemax of hydrogen fuel can be higher than that of methane and propane fuels for a system with a medium level of waste heat recovery and operated at 700 ℃≤T≤900 ℃.展开更多
Using an engineering perspective which is looking at the hair cells cilia as a total entity interacting with its neighboring cilia along their entire length, a theory of capacitive transduction is developed. This larg...Using an engineering perspective which is looking at the hair cells cilia as a total entity interacting with its neighboring cilia along their entire length, a theory of capacitive transduction is developed. This larger scaled view of cilia interaction suggests that transduction may be achieved through a mechanically controlled variable capacitor in the cilia bundle. A brief review of some seldom considered facts about electrical capacitors supports the hypothesis presented. Experimental measurements of hair cell reversal potential and ionic conditions surrounding the cilia during transduction, long reported in the biophysical literature, also support a capacitive hypothesis of transduction.展开更多
The redox reaction of gold III chloride in acid solutions has been electro-chemically investigated using a cyclic voltammetry technique. This paper emphasizes the current and potential sites at which gold III chloride...The redox reaction of gold III chloride in acid solutions has been electro-chemically investigated using a cyclic voltammetry technique. This paper emphasizes the current and potential sites at which gold III chloride is reduced in hydrochloric acid that is vital to electrochemical evaluation of gold recovery. The solutions were prepared by reacting HCl with AuCl3 in various concentrations thus 30 and 60 mg/L AuCl3 in 0.1 and 0.5 M HCl, respectively. Solutions of 0.1 and 0.5 M HCl containing 0, 30 and 60 mg/L AuCl3, respectively were tested for possible reduction and oxidation reactions by cyclic voltammogram experiment using a glassy carbon, a saturated calomel and a platinum wire mesh as working, reference and counter electrodes, respectively. The results showed no peak in the case of the absence of AuCl3 in the solutions, but appreciable cathodic and anodic peaks for the reduction and oxidation of various concentrations of AuCl3 in acid solutions. The reaction between AuCl3 and HCl was found to be reversible because the ratio of oxidation peak current and reduction peak current was 1. The concentration of AuCl-4 on the surface of the working electrode at the reduction site for each AuCl3 concentration using Nernst equation was 1.22 × 109 ppm and 2.44 × 109 ppm. The reduction potentials were independent of concentration, while the current was highly dependent of concentration.展开更多
Loschmidt’s paradox is extended by replacing its assumption of time reversibility with full CPT symmetry. Mobility is identified as a means for expressing collisions or dissipation, and the cross product of its gradi...Loschmidt’s paradox is extended by replacing its assumption of time reversibility with full CPT symmetry. Mobility is identified as a means for expressing collisions or dissipation, and the cross product of its gradient with the magnetic field, for expressing parity. Three phenomena incorporating such cross products are identified. The first is the cross product of the mobility gradient with the magnetic field. The second combines this cross product with the E cross B drift. The third is the reciprocal of the Nernst effect expressed as a cross product of the temperature gradient and the magnetic field. Simulations are conducted for testing Loschmidt’s extended paradox. Onsager’s exclusion of magnetic fields and rotation from reciprocals violates CPT symmetry and is unjustified. All three cross-product phenomena skew statistics in a fashion unanticipated by Boltzmann’s assumptions in his H-Theorem. CPT symmetric systems fall outside the assumptions of the theorem which is not rendered invalid but simply limited to its domain of applicability. Therefore, these systems do not violate the second law as Boltzmann defines it. They bypass it.展开更多
The Seebeck effect encounters a few fundamental constraints hindering its thermoelectric(TE)conversion efficiency.Most notably,there are the charge compensation of electrons and holes that diminishes this effect,and t...The Seebeck effect encounters a few fundamental constraints hindering its thermoelectric(TE)conversion efficiency.Most notably,there are the charge compensation of electrons and holes that diminishes this effect,and the Wiedemann-Franz(WF)law that makes independent optimization of the corresponding electrical and thermal conductivities impossible.Here,we demonstrate that in the topological Dirac semimetal Cd3As2 the Nernst effect,i.e.,the transverse counterpart of the Seebeck effect,can generate a large TE figure of merit zNT.At room temperature,zNT≈0.5 in a small field of 2 T and it significantly surmounts its longitudinal counterpart for any field.A large Nernst effect is generically expected in topological semimetals,benefiting from both the bipolar transport of compensated electrons and holes and their high mobilities.In this case,heat and charge transport are orthogonal,i.e.,not intertwined by the WF law anymore.More importantly,further optimization of zNT by tuning the Fermi level to the Dirac node can be anticipated due to not only the enhanced bipolar transport,but also the anomalous Nernst effect arising from a pronounced Berry curvature.A combination of the topologically trivial and nontrivial advantages promises to open a new avenue towards high-efficient transverse thermoelectricity.展开更多
The influence of magnetic field on the redox potentials of the Nernst equation. The author offered the new formula Nernst equation in a magnetic field. Our proposed formula takes into account the influence of the magn...The influence of magnetic field on the redox potentials of the Nernst equation. The author offered the new formula Nernst equation in a magnetic field. Our proposed formula takes into account the influence of the magnetic field on the redox processes.展开更多
Considering the relationship between the black hole horizon and the cosmological horizon, the thermodynamic property of the charged de Sitter spacetime is discussed. The effective temperature and energy are obtained. ...Considering the relationship between the black hole horizon and the cosmological horizon, the thermodynamic property of the charged de Sitter spacetime is discussed. The effective temperature and energy are obtained. The result shows that the upper limit of the energy in the charged de Sitter spacetime is just the energy in the pure de Sitter spacetime. The thermal capacity of the charged de Sitter spacetime is positive, thus satisfying the thermal stability condition.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 12075197)the Fundamental Research Fund for the Central Universities of China (Grant No. 20720210020)。
文摘It is found from textbooks and literature that there are three different statements for the third law of thermodynamics,i.e., the Nernst theorem, the unattainability statement of absolute zero temperature, and the heat capacity statement. It is pointed out that such three statements correspond to three thermodynamic parameters, which are, respectively, the entropy,temperature, and heat capacity, and can be obtained by extrapolating the experimental results of different parameters at ultralow temperatures to absolute zero. It is expounded that because there is no need for additional assumptions in the derivation of the Nernst equation, the Nernst theorem should be renamed as the Nernst statement. Moreover, it is proved that both the Nernst statement and the heat capacity statement are mutually deducible and equivalent, while the unattainability of absolute zero temperature is only a corollary of the Nernst statement or the heat capacity statement so that it is unsuitably referred to as one statement of the third law of thermodynamics. The conclusion is that the Nernst statement and the heat capacity statement are two equivalent statements of the third law of thermodynamics.
基金support by National Natural Science Foundation of China (Grant No. 11904040)Chongqing Research Program of Basic Research and Frontier Technology,China (Grant No. cstc2020jcyj-msxm X0263)Chinesisch-Deutsche Mobilit?tsprogamm of Chinesisch-Deutsche Zentrum für Wissenschaftsf?rderung (Grant No. M-0496)。
文摘The interplay between lattice geometry,band topology and electronic correlations in the newly discovered kagome compounds AV3Sb5(A=K,Rb,Cs) makes this family a novel playground to investigate emergent quantum phenomena,such as unconventional superconductivity,chiral charge density wave and electronic nematicity.These exotic quantum phases naturally leave nontrivial fingerprints in transport properties of AV3Sb5,both in electrical and thermal channels,which are prominent probes to uncover the underlying mechanisms.In this brief review,we highlight the unusual electrical and thermal transport properties observed in the unconventional charge ordered state of A V3Sb5,including giant anomalous Hall,anomalous Nernst,ambipolar Nernst and anomalous thermal Hall effects.Connections of these anomalous transport properties to time-reversal symmetry breaking,topological and multiband fermiology,as well as electronic nematicity,are also discussed.Finally,a perspective together with challenges of this rapid growing field are given.
基金Project supported in part by the National Key R&D Program of China(Grant No.2018YFA0305800)the National Natural Science Foundation of China(Grant Nos.11974348 and 11834014)+2 种基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB28000000 and XDB33000000)supported in part by the Training Program of Major Research plan of the National Natural Science Foundation of China(Grant No.92165105)CAS Project for Young Scientists in Basic Research(Grant No.YSBR-057)。
文摘Valley Nernst effect is a newly proposed and experimentally confirmed effect,which could be used to design novel thermoelectric devices.We study the valley Nernst effect in(M+N)-layer twisted multilayer graphene systems by a simple low-energy effective model.It is found that the total valley Nernst coefficient(VNC)is three orders of magnitude larger than that in monolayer group-Ⅵdichalcogenides.The total VNC increases with the increase of layer numbers.It is shown that the total VNC exhibits a structure with three peaks as a function of the Fermi energy.We identify that the central peak is always negative stemming from the flat band.Two shoulder peaks are positively induced by the conduction and valence bands,respectively.These predicted features can be tested experimentally.The present work would shed more light on valley caloritronics.
基金This work was supported by JSPS KAKENHI(JP19H05815 and JP21J12566),JST-CREST(Grant No.JPMJCR2204)MEXT as part of the“Program for Promoting Research on the Supercomputer Fugaku(Fugaku Battery&Fuel Cell Project),grant number JPMXP1020200301”+1 种基金The calculations were carried out on the supercomputers at the National Institute for Materials Science(NIMS),the TSUBAME 3.0 at the Tokyo Institute of Technology(MEXT Project of the TAC-MI)the supercomputer Fugaku at the RIKEN through the HPCI Systems(HPCI System Research Projects(hp200131 and hp210173)).
文摘Condensed matters with high ionic conductivities are crucial in various solid devices such as solid-state batteries. The conduction ischaracterized by the cooperative ionic motion associated with the high carrier density. However, the high cost of computingcorrelated ionic conductivities has forced almost all ab initio molecular dynamics (MD) to rely on the Nernst–Einstein dilute-solutionapproximation, which ignores the cross-correlation effect. Here we develop a chemical color-diffusion nonequilibrium MD (CCD-NEMD) method, which enables to calculate the correlated conductivities with fewer sampling steps than the conventional MD. ThisCCD-NEMD is demonstrated to well evaluate the conductivities in the representative solid electrolyte bulk Li10GeP2S12 andLi_(7)La_(3)Zr_(2)O_(12). We also applied CCD-NEMD to the grain boundary of Li_(7)La_(3)Zr_(2)O_(12) and demonstrated its applicability for calculatinginterfacial local conductivities, which is essential for investigating grain boundaries and composite electrolytes. CCD-NEMD canprovide further accurate understanding of ionics with ionic correlations and promote developing solid devices.
基金This work is financially supported by the European Research Council(ERC Advanced Grant no.742068‘TOPMAT’)We also acknowledge funding by the DFG through SFB 1143(project ID.247310070)+3 种基金the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter ct.qmat(EXC2147,project ID.39085490)M.G.V.and I.R.thanks support from the Spanish Ministerio de Ciencia e Innovacion(grant PID2019-109905GB-C21)European Research Council(ERC)grant agreement no.101020833M.G.V.and C.F.acknowledge support by the Deutsche Forschungsge-meinschaft(DFG,German Research Foundation)-FOR 5249(QUAST).
文摘Magnetism and spin-orbit coupling are two fundamental and interconnected properties of oxide materials,that can give rise to various topological transport phenomena,including anomalous Hall and anomalous Nernst effects.These transport responses can be significantly enhanced by designing an electronic structure with a large Berry curvature.In this context,rocksalt-ordered double perovskites(DP),denoted as A2BB’O6,with two distinct transition metal sites are very powerful platforms for exploration and research.In this work,we present a comprehensive study based on the intrinsic anomalous transport in cubic and tetragonal stable DP compounds with 3d-4d/5d elements.Our findings reveal that certain DP compounds show a large anomalous Hall effect,displaying topological band crossings in the proximity of the Fermi energy.
基金This work was supported by the National Key R&D Program of China under Grant No.2019YFA0704900Guangdong Provincial Key Laboratory for Computational Science and Material Design under Grant No.2019B030301001+2 种基金the Science,Technology and Innovation Commission of Shenzhen Municipality(No.ZDSYS20190902092905285)Center for Computational Science and Engineering of Southern University of Science and TechnologyX.S.W.acknowledges financial support from the National Key R&D Program of China under Grant No.2022YFA1403700 and NSFC under Grant No.12074009.
文摘Anomalous Nernst effect generates a transverse voltage perpendicular to the temperature gradient.It has several advantages compared with the longitudinal thermoelectricity for energy conversion,such as decoupling of electronic and thermal transports,higher flexibility,and simpler lateral structure.However,a design principle beyond specific materials systems for obtaining a large anomalous Nernst conductivity(ANC)is still absent.In this work,we theoretically demonstrate that a pair of Dirac nodes under a Zeeman field manifests an odd-distributed,double-peak anomalous Hall conductivity curve with respect to the chemical potential and a compensated carrier feature,leading to an enhanced ANC compared with that of a simple Weyl semimetal with two Weyl nodes.Based on first-principles calculations,we then provide two Dirac semimetal candidates,i.e.,Na3Bi and NaTeAu,and show that under a Zeeman field,they exhibit a sizable ANC value of 0.4 Am^(-1)K^(-1) and 1.3 Am^(-1)K^(-1),respectively,near the Fermi level.Such an approach is also applicable to ferromagnetic materials with intrinsic Zeeman splitting,as exemplified by a hypothetical alloy NaFeTe2Au2,exhibiting an ANC as high as 3.7 Am^(-1)K^(-1) at the Fermi level.Our work provides a design principle with a prototype band structure for enhanced ANC pinning at the Fermi level,shedding light on the inverse design of other specific functional materials based on electronic structure.
文摘The unattainability of the absolute zero of temperature is proved by using Carnot’s theorem. Hence this unattainability is distinct from the Planck-Fer-mi statement of the Third Law of Thermodynamics that the entropy vanishes at ?T=0. It is shown that the isothermal compressibility KT is in general larger than the adiabatic compressibility Ks and the difference KT?−?Ks?vanishes in the low temperature limit.
基金This work was financially supported by the ERC Advanced Grant No.291472‘Idea Heusler’ERC Advanced Grant No.742068‘TOPMAT’EC project FET-OPEN No.829044‘SCHINES’.
文摘The interplay of magnetism and topology opens up the possibility for exotic linear response effects,such as the anomalous Hall effect and the anomalous Nernst effect,which can be strongly enhanced by designing a large Berry curvature in the electronic structure.Magnetic Heusler compounds are a promising class of materials for this purpose because they are versatile,show magnetism,and their electronic structure hosts strong topological features.Here,we provide a comprehensive study of the intrinsic anomalous transport for magnetic cubic full Heusler compounds and we illustrate that several Heusler compounds outperform the best so far reported materials.The results reveal the importance of symmetries,especially mirror planes,in combination with magnetism for giant anomalous Hall and Nernst effects,which should be valid in general for linear responses(spin Hall effect,spin orbital torque,etc.)dominated by intrinsic contributions.
文摘A simple rational model is proposed for discharge of batteries with aqueous electrolytes, based on Nernst equation. Details of electrode kinetics are not taken into account. Only a few overall parameters of the battery are considered. A simple algorithm, with variable time step-length <span style="font-family:Verdana;">Δ</span><i><span style="font-family:Verdana;">t</span></i><span style="font-family:Verdana;">, is presented, for proposed model. The model is first applied to Daniel cell, in order to clar</span><span style="font-family:Verdana;">ify</span><span style="font-family:""><span style="font-family:Verdana;"> concepts and principles of battery operation. It is found that initial pinching, in time-history curve of voltage </span><i><span style="font-family:Verdana;">E-t</span></i><span style="font-family:Verdana;">, is due to initial under-concentration of product ion. Then, model is applied </span></span><span style="font-family:Verdana;">to</span><span> a lead-acid battery. In absence of an ion product, and in order to construct nominator of Nernst ratio, such an ion, with coefficient tending to zero, is assumed, thus yielding unity in nominator. Time-history curves of voltage, for various values of internal resistance, are compared with corresponding published experimental curves. Temperature effect on voltage-time curve is examined. Proposed model can be extended to other types of batteries, which can be considered as having aqueous electrolytes, too.</span>
基金This work was supported by the National Natural Science Foundation of China(No.11574284 and No.11774324),the National Basic Research Program of China(No.2012CB215405)and Collaborative Innovation Center of Suzhou Nano Science and Technology.
文摘The maximum electrical efficiency of fuel cell system,ηemax, is important for the understanding and development of the fuel cell technology. Attempt is made to build a theory for ηemaxby considering the energy requirement of heating the fuel and air streams to the fuel cell operating temperature T. A general thermodynamic analysis is performed and the energy balances for the overall operating processes of a fuel cell system are established. Explicit expressions for the determination of ηemax are deduced. Unlike the Carnot efficiency,ηemaxis found to be fuel specific. Except for hydrogen fuel, chemical equilibrium calculations are necessary to compute ηemax.Analytical solutions for the chemical equilibrium of alkane fuels are presented. The theoretical model is used to analyze the effects of T and the steam contents of CH4, C3 H8,and H2 on ηemax for systems with various degrees of waste heat recovery.Contrary to the common perception concerning methane and propane fuels, ηemax decreases substantially with the increase of T. Moreover, ηemax of hydrogen fuel can be higher than that of methane and propane fuels for a system with a medium level of waste heat recovery and operated at 700 ℃≤T≤900 ℃.
文摘Using an engineering perspective which is looking at the hair cells cilia as a total entity interacting with its neighboring cilia along their entire length, a theory of capacitive transduction is developed. This larger scaled view of cilia interaction suggests that transduction may be achieved through a mechanically controlled variable capacitor in the cilia bundle. A brief review of some seldom considered facts about electrical capacitors supports the hypothesis presented. Experimental measurements of hair cell reversal potential and ionic conditions surrounding the cilia during transduction, long reported in the biophysical literature, also support a capacitive hypothesis of transduction.
文摘The redox reaction of gold III chloride in acid solutions has been electro-chemically investigated using a cyclic voltammetry technique. This paper emphasizes the current and potential sites at which gold III chloride is reduced in hydrochloric acid that is vital to electrochemical evaluation of gold recovery. The solutions were prepared by reacting HCl with AuCl3 in various concentrations thus 30 and 60 mg/L AuCl3 in 0.1 and 0.5 M HCl, respectively. Solutions of 0.1 and 0.5 M HCl containing 0, 30 and 60 mg/L AuCl3, respectively were tested for possible reduction and oxidation reactions by cyclic voltammogram experiment using a glassy carbon, a saturated calomel and a platinum wire mesh as working, reference and counter electrodes, respectively. The results showed no peak in the case of the absence of AuCl3 in the solutions, but appreciable cathodic and anodic peaks for the reduction and oxidation of various concentrations of AuCl3 in acid solutions. The reaction between AuCl3 and HCl was found to be reversible because the ratio of oxidation peak current and reduction peak current was 1. The concentration of AuCl-4 on the surface of the working electrode at the reduction site for each AuCl3 concentration using Nernst equation was 1.22 × 109 ppm and 2.44 × 109 ppm. The reduction potentials were independent of concentration, while the current was highly dependent of concentration.
文摘Loschmidt’s paradox is extended by replacing its assumption of time reversibility with full CPT symmetry. Mobility is identified as a means for expressing collisions or dissipation, and the cross product of its gradient with the magnetic field, for expressing parity. Three phenomena incorporating such cross products are identified. The first is the cross product of the mobility gradient with the magnetic field. The second combines this cross product with the E cross B drift. The third is the reciprocal of the Nernst effect expressed as a cross product of the temperature gradient and the magnetic field. Simulations are conducted for testing Loschmidt’s extended paradox. Onsager’s exclusion of magnetic fields and rotation from reciprocals violates CPT symmetry and is unjustified. All three cross-product phenomena skew statistics in a fashion unanticipated by Boltzmann’s assumptions in his H-Theorem. CPT symmetric systems fall outside the assumptions of the theorem which is not rendered invalid but simply limited to its domain of applicability. Therefore, these systems do not violate the second law as Boltzmann defines it. They bypass it.
基金the Ministry of Science and Technology of China(Grant Nos.2017YFA0303100,and 2015CB921303)the National Natural Science Foundation of China(Grant Nos.11774404,and11474332)the Chinese Academy of Sciences through the Strategic Priority Research Program(Grant No.XDB07020200)。
文摘The Seebeck effect encounters a few fundamental constraints hindering its thermoelectric(TE)conversion efficiency.Most notably,there are the charge compensation of electrons and holes that diminishes this effect,and the Wiedemann-Franz(WF)law that makes independent optimization of the corresponding electrical and thermal conductivities impossible.Here,we demonstrate that in the topological Dirac semimetal Cd3As2 the Nernst effect,i.e.,the transverse counterpart of the Seebeck effect,can generate a large TE figure of merit zNT.At room temperature,zNT≈0.5 in a small field of 2 T and it significantly surmounts its longitudinal counterpart for any field.A large Nernst effect is generically expected in topological semimetals,benefiting from both the bipolar transport of compensated electrons and holes and their high mobilities.In this case,heat and charge transport are orthogonal,i.e.,not intertwined by the WF law anymore.More importantly,further optimization of zNT by tuning the Fermi level to the Dirac node can be anticipated due to not only the enhanced bipolar transport,but also the anomalous Nernst effect arising from a pronounced Berry curvature.A combination of the topologically trivial and nontrivial advantages promises to open a new avenue towards high-efficient transverse thermoelectricity.
文摘The influence of magnetic field on the redox potentials of the Nernst equation. The author offered the new formula Nernst equation in a magnetic field. Our proposed formula takes into account the influence of the magnetic field on the redox processes.
基金supported by the National Natural Science Foundation of China (Grant No. 11075098)the Doctoral Sustentation Fund of Shanxi Datong University of China
文摘Considering the relationship between the black hole horizon and the cosmological horizon, the thermodynamic property of the charged de Sitter spacetime is discussed. The effective temperature and energy are obtained. The result shows that the upper limit of the energy in the charged de Sitter spacetime is just the energy in the pure de Sitter spacetime. The thermal capacity of the charged de Sitter spacetime is positive, thus satisfying the thermal stability condition.
