This paper develops a generalized scalar auxiliary variable(SAV)method for the time-dependent Ginzburg-Landau equations.The backward Euler method is used for discretizing the temporal derivative of the time-dependent ...This paper develops a generalized scalar auxiliary variable(SAV)method for the time-dependent Ginzburg-Landau equations.The backward Euler method is used for discretizing the temporal derivative of the time-dependent Ginzburg-Landau equations.In this method,the system is decoupled and linearized to avoid solving the non-linear equation at each step.The theoretical analysis proves that the generalized SAV method can preserve the maximum bound principle and energy stability,and this is confirmed by the numerical result,and also shows that the numerical algorithm is stable.展开更多
We consider a five-dimensional Minkowski space with two time dimensions characterized by distinct speeds of causality and three space dimensions. Formulas for relativistic coordinate and velocity transformations are d...We consider a five-dimensional Minkowski space with two time dimensions characterized by distinct speeds of causality and three space dimensions. Formulas for relativistic coordinate and velocity transformations are derived, leading to a new expression for the speed limit. Extending the ideas of Einstein’s Theory of Special Relativity, concepts of five-velocity and five-momenta are introduced. We get a new formula for the rest energy of a massive object. Based on a non-relativistic limit, a two-time dependent Schrödinger-like equation for infinite square-well potential is developed and solved. The extra time dimension is compactified on a closed loop topology with a period matching the Planck time. It generates interference of additional quantum states with an ultra-small period of oscillation. Some cosmological implications of the concept of four-dimensional versus five-dimensional masses are briefly discussed, too.展开更多
We report theoretical studies on the plasmon resonances in linear Au atomic chains by using ab initio time- dependent density functional theory. The dipole responses are investigated each as a function of chain length...We report theoretical studies on the plasmon resonances in linear Au atomic chains by using ab initio time- dependent density functional theory. The dipole responses are investigated each as a function of chain length. They converge into a single resonance in the longitudinal mode but split into two transverse modes. As the chain length increases, the longitudinal plasmon mode is redshifted in energy while the transverse modes shift in the opposite direction (blueshifts). In addition, the energy gap between the two transverse modes reduces with chain length increasing. We find that there are unique characteristics, different from those of other metallic chains. These characteristics are crucial to atomic-scale engineering of single-molecule sensing, optical spectroscopy, and so on.展开更多
This paper presents a three-dimensional time-dependent nonlinear theory of helix traveling wave tubes for beam- wave interaction. The radio frequency electromagnetic fields are represented as the superposition of azim...This paper presents a three-dimensional time-dependent nonlinear theory of helix traveling wave tubes for beam- wave interaction. The radio frequency electromagnetic fields are represented as the superposition of azimuthally sym- metric waves in a vacuum sheath helix. Coupling impedance is introduced to the electromagnetic field equations' stimulating sources, which makes the theory easier and more flexible to realize. The space charge fields are calculated by electron beam space-charge waves expressed as the superposition solutions of Helmholtz equations. The focusing forces due to either a solenoidal field or a periodic permanent magnetic field is also included. The dynamical equations of electrons are Lorentz equations associating with electromagnetic fields, focusing fields and space-charge fields. The numerically simulated results of a tube are presented.展开更多
Time-dependent density functional theory(TDDFT) method is used to investigate the details of the excited state intramolecular proton transfer(ESIPT) process and the mechanism for temperature effect on the Enol*/K...Time-dependent density functional theory(TDDFT) method is used to investigate the details of the excited state intramolecular proton transfer(ESIPT) process and the mechanism for temperature effect on the Enol*/Keto*emission ratio for the Me2N-substited flavonoid(MNF) compound. The geometric structures of the S0 and S1 states are denoted as the Enol, Enol*, and Keto*. In addition, the absorption and fluorescence peaks are also calculated. It is noted that the calculated large Stokes shift is in good agreement with the experimental result. Furthermore, our results confirm that the ESIPT process happens upon photoexcitation, which is distinctly monitored by the formation and disappearance of the characteristic peaks of infrared(IR) spectra involved in the proton transfer and in the potential energy curves. Besides, the calculations of highest occupied molecular orbital(HOMO) and lowest unoccupied molecular orbital(LUMO) reveal that the electronegativity change of proton acceptor due to the intramolecular charge redistribution in the S1 state induces the ESIPT. Moreover, the thermodynamic calculation for the MNF shows that the Enol*/Keto*emission ratio decreasing with temperature increasing arises from the barrier lowering of ESIPT.展开更多
Electronic properties, such as HOMO and LUMO energies, band gaps, ionization potential (IP) and electron affinity (EA) of 2,7- and 3,6-1inked carbazole trimers, two conjugated oligomcrs with different linkages of ...Electronic properties, such as HOMO and LUMO energies, band gaps, ionization potential (IP) and electron affinity (EA) of 2,7- and 3,6-1inked carbazole trimers, two conjugated oligomcrs with different linkages of carbazole, were studicd by the density functional theory with Becke-Lee-Young-Parr composite exchange correlation functional (B3LYP). The absorption spectra of these compounds were also investigated by time-dependent density functional theory (TD-DFT) with 6-3 IG* basis set. The calculated results indicated that the HOMO and LUMO of the 2,7- and 3,6-1inked carbazole trimers are both slightly destabilized on going from methyl substitution to sec-butyl substitution. Both IP and EA exhibit their good hole-transporting but poor electronaccepting ability. The presence of alkyl groups on the nitrogen atoms does not affect the intra-chain electronic delocalization along the molecular frame. Thus no significant effect on the band gap and absorption spectra of compounds has been found.展开更多
The macroscopic electromagnetic properties of type-II superconductors are mainly influenced by the behavior of micro-scopic superconducting flux quantum units.Time-dependent Ginzburg-Landau(TDGL)theory is a well-known...The macroscopic electromagnetic properties of type-II superconductors are mainly influenced by the behavior of micro-scopic superconducting flux quantum units.Time-dependent Ginzburg-Landau(TDGL)theory is a well-known tool for describing and examining both the statics and dynamics of these superconducting entities.It have been instrumental in replicating and elucidat-ing numerous experimental results over the past decades.This paper provides a comprehensive overview of the progress in TDGL simulations,focusing on three key aspects of superconductor applications.We delve first into vortex rectification in supercon-ductors described within the TDGL framework,specifically highlighting the achievement of superconducting diode effect through asymmetric pinning landscapes and the reversible manipulation of vortex ratchets with dynamic pinning landscapes.In terms of the achievements of TDGL simulations concerning the critical current density of superconductors,we emphasize particularly on the optimization of pinning sites,including vortex pinning and dynamics in polycrystalline Nb3Sn with grain boundaries.In the third aspect,we concentrate on numerical modeling of vortex penetration and dynamics in superconducting radio-frequency cavities,including a discussion on superconductor-insulator-superconductor multilayer structures.Finally,we present key findings,insights,and perspectives derived from the discussed simulations.展开更多
Wellbore stability is a key to have a successful drilling operation.Induced stresses are the main factors affecting wellbore instability and associated problems in drilling operations.These stresses are significantly ...Wellbore stability is a key to have a successful drilling operation.Induced stresses are the main factors affecting wellbore instability and associated problems in drilling operations.These stresses are significantly impacted by pore pressure variation and thermal stresses in the field.In order to address wellbore instability problems,it is important to investigate the mechanisms of rockefluid interaction with respect to thermal and mechanical aspects.In order to understand the induced stresses,different mathematical models have been developed.In this study,the field equations governing the problem have been derived based on the thermo-poroelastic theory and solved analytically in Laplace domain.The results are transferred to time domain using Fourier inverse method.Finite difference method is also utilized to validate the results.Pore pressure and temperature distributions around the wellbore have been focused and simulated.Next,induced radial and tangential stresses for different cases of cooling and heating of formation are compared.In addition,the differences between thermo-poroelastic and poroelastic models in situation of permeable and impermeable wellbores are described.It is observed that cooling and pore pressure distribution reinforce the induced radial stress.Whereas cooling can be a tool to control and reduce tangential stress induced due to invasion of drilling fluid.In the next step,safe mud window is obtained using Mohr-Coulomb,Mogi-Coulomb,and modified Lade failure criteria for different inclinations.Temperature and pore pressure distributions do not change the minimum allowable wellbore pressure significantly.However,upper limit of mud window is sensitive to induced stresses and it seems vital to consider changes in temperature and pore pressure to avoid any failures.The widest and narrowest mud windows are proposed by modified Lade and Mohr-Coulomb failure criteria,respectively.展开更多
The relationship between quantum mechanics and classical mechanics is investigated by taking a Gaussian-type wave packet as a solution of the Schr o¨dinger equation for the Caldirola–Kanai oscillator driven by a...The relationship between quantum mechanics and classical mechanics is investigated by taking a Gaussian-type wave packet as a solution of the Schr o¨dinger equation for the Caldirola–Kanai oscillator driven by a sinusoidal force. For this time-dependent system, quantum properties are studied by using the invariant theory of Lewis and Riesenfeld. In particular,we analyze time behaviors of quantum expectation values of position and momentum variables and compare them to those of the counterpart classical ones. Based on this, we check whether the Ehrenfest theorem which was originally developed in static quantum systems can be extended to such time-varying systems without problems.展开更多
The photodetachment dynamics of H^- ion in a harmonic potential plus an oscillating electric field is studied using the time-dependent closed orbit theory. An analytical formula for calculating the photodetachment cro...The photodetachment dynamics of H^- ion in a harmonic potential plus an oscillating electric field is studied using the time-dependent closed orbit theory. An analytical formula for calculating the photodetachment cross section of this system is put forward. It is found that the photodetachment cross section of this system is nearly unaffected for the weak oscillating electric field strength, but oscillates complicatedly when the oscillating electric field strength turns strong. In addition, the frequency of the harmonic potential and the oscillating electric field (the frequency of the harmonic potential and the frequency of the oscillating electric field are the same in the paper, unless otherwise stated.) can also affect the photodetachment dynamics of this system. With the increase of the frequency in the harmonic potential and the oscillating electric field, the number of the closed orbits for the detached electrons increased, which makes the oscillatory structure in the photodetachment cross section much more complex. Our study presents an intuitive understanding of the photodetachment dynamics driven by a harmonic potential plus an oscillating electric field from a space and time dependent viewpoint. This study is very useful in guiding the future experimental research for the photodetachment dynamics in the electric field both changing with space and time.展开更多
By using first-principles simulations based on time-dependent density functional theory, the chemical reaction of an HCl molecule encapsulated in C60 induced by femtosecond laser pulses is observed. The H atom starts ...By using first-principles simulations based on time-dependent density functional theory, the chemical reaction of an HCl molecule encapsulated in C60 induced by femtosecond laser pulses is observed. The H atom starts to leave the Cl atom and is reflected by the C60 wall. The coherent nuclear dynamic behaviors of bond breakage and recombination of the HCl molecule occurring in both polarized parallel and perpendicular to the H-Cl bond axis are investigated. The radial oscillation is also found in the two polarization directions of the laser pulse. The relaxation time of the H-Cl bond lengths in transverse polarization is slow in comparison with that in longitudinal polarization. Those results are important for studying the dynamics of the chemical bond at an atomic level.展开更多
Alloy nanostructures supporting localized surface plasmon resonances has been widely used as efficient photocatalysts,but the microscopic mechanism of alloy compositions enhancing the catalytic efficiency is still unc...Alloy nanostructures supporting localized surface plasmon resonances has been widely used as efficient photocatalysts,but the microscopic mechanism of alloy compositions enhancing the catalytic efficiency is still unclear.By using time-dependent density functional theory(TDDFT),we analyze the real-time reaction processes of plasmon-mediated H_(2) splitting on linear Ag-Au alloy chains when exposed to femtosecond laser pulses.It is found that H_(2) splitting rate depends on the position and proportion of Au atoms in alloy chains,which indicates that specially designed Ag-Au alloy is more likely to induce the reaction than pure Ag chain.Especially,more electrons directly transfer from the alloy chain to the anti-bonding state of H_(2),thereby accelerating the H_(2) splitting reaction.These results establish a theoretical foundation for comprehending the microscopic mechanism of plasmon-induced chemical reaction on the alloy nanostructures.展开更多
The plasmon-induced nonlinear response has attracted great attention in micro-nano optics and optoelectronics applications,yet the underlying microscopic mechanism remains elusive.In this study,the nonlinear response ...The plasmon-induced nonlinear response has attracted great attention in micro-nano optics and optoelectronics applications,yet the underlying microscopic mechanism remains elusive.In this study,the nonlinear response of gold nanoclusters when exposed to a femtosecond laser pulse was investigated using time-dependent density functional theory.It was observed that the third-order tunneling current was augmented in plasmonic dimers,owing to a greater number of electrons in the dimer being excited from occupied to unoccupied states.These findings provide profound theoretical insights and enable the realization of accurate regulation and control of nonlinear effects induced by plasmons at the atomic level.展开更多
In this paper, we prove the existence of global classical solutions to time-dependent Ginzburg-Landau(TDGL) equations. By the properties of Besov and Sobolev spaces, together with the energy method, we establish the...In this paper, we prove the existence of global classical solutions to time-dependent Ginzburg-Landau(TDGL) equations. By the properties of Besov and Sobolev spaces, together with the energy method, we establish the global existence and uniqueness of classical solutions to the initial boundary value problem for time-dependent Ginzburg-Landau equations.展开更多
To investigate the collision processes of proton with the water dimer(H_(2)O)_(2)at 50 e V,the time-dependent density functional theory coupled with molecular dynamics nonadiabatically is applied.Six specific collisio...To investigate the collision processes of proton with the water dimer(H_(2)O)_(2)at 50 e V,the time-dependent density functional theory coupled with molecular dynamics nonadiabatically is applied.Six specific collision orientations with various impact parameters are considered.The reaction channels,the mass distribution and the fragmentation mass spectrum are explored.Among all launched samples,the probability of the channel of non-charge transfer scattering and charge transfer scattering is about 80%,hinting that the probability of fragmentation is about 20%.The reaction channel of proton exchange process 2 is taken as an example to exhibit the detailed microscopic dynamics of the collision process by inspecting the positions,the respective distance,the number of loss of electrons and the evolution of the electron density.The study of the mass distribution and the fragmentation mass spectrum shows that among all possible fragments,the fragment with mass 36 has the highest relative abundance of 65%.The relative abundances of fragments with masses 1,35,and 34are 20%,13%,and 1.5%,respectively.For the total electron capture cross section,the present calculations agree with the available measurements and calculations over the energy range from 50 e V to 12 ke V.展开更多
The origins of superconductivity and pairing symmetry of order parameters are still controversial problems for FeSe thin films up to date.Under the Neumann boundary conditions,the electromagnetic properties of this sy...The origins of superconductivity and pairing symmetry of order parameters are still controversial problems for FeSe thin films up to date.Under the Neumann boundary conditions,the electromagnetic properties of this system are investigated using the two-band Ginzburg-Landau theory.We calculate the temperature dependence of upper critical field in arbitrary direction and critical supercurrent density through the FeSe film.It is revealed that the normalized upper critical field is independent of the film thickness and all of our theoretical results are in accordance with the experimental data.These thus strongly indicate the existence of two-gap s-wave superconductivity in this material.展开更多
Relationship of plasmonic properties of multiple clusters to molecular interactions and properties of a single cluster or molecule have become increasingly important due to the continuous emergence of molecular and cl...Relationship of plasmonic properties of multiple clusters to molecular interactions and properties of a single cluster or molecule have become increasingly important due to the continuous emergence of molecular and cluster devices or systems.A hybrid phenomenon similar to plasmonic nanoparticle hybridization exists between two molecules with plasmon excitation modes.We use linear-response time-dependent density functional theory,real-time propagation time-dependent density functional theory,the plasmonicity index,and transition contribution maps(TCMs)to identify the plasmon excitation modes for the linear polyenes octatetraene with–OH and–NH_(2)groups and analyze the hybridization characteristics using charge transitions.The results show that molecular plasmon hybridization exists when the two molecules are coupled.The TCM analysis shows that the plasmon modes and hybridization result from collective and single-particle excitation.The plasmon mode is stronger,and the individual properties of the molecules are maintained after coupling when there is extra charge depose in the molecules because the electrons are moving in the molecules.This study provides new insights into the molecular plasmon hybridization of coupled molecules.展开更多
High-order harmonic generation of the cyclo[18]carbon(C_(18) ) molecule under few-cycle circularly polarized laser pulse is studied by time-dependent density functional theory. Compared with the harmonic emission of t...High-order harmonic generation of the cyclo[18]carbon(C_(18) ) molecule under few-cycle circularly polarized laser pulse is studied by time-dependent density functional theory. Compared with the harmonic emission of the ring molecule C_(6)H_(6) having similar ionization potential, the C_(18) molecule has higher efficiency and cutoff energy than C_(6)H_(6) with the same laser field parameters. Further researches indicate that the harmonic efficiency and cutoff energy of the C_(18) molecule increase gradually with the increase of the laser intensity of the driving laser or decrease of the wavelength, both are larger than those of the C_(6)H_(6) molecule. Through the analysis of the time-dependent evolution of the electronic wave packets, it is also found that the higher efficiency of harmonic generation can be attributed to the larger spatial scale of the C_(18) molecule,which leads to a greater chance for the ionized electrons from one atom to recombine with others of the parent molecule.Selecting the suitable driving laser pulse, it is demonstrated that high-order harmonic generation in the C_(18) molecule has a wide range of applications in producing circularly polarized isolated attosecond pulse.展开更多
Excited-state intramolecular proton transfer(ESIPT) molecules are broadly applied to UV absorbers, fluorescence sensing, and lighting materials. In previous work, the fluorescence colors of oxazoline-substituted hydro...Excited-state intramolecular proton transfer(ESIPT) molecules are broadly applied to UV absorbers, fluorescence sensing, and lighting materials. In previous work, the fluorescence colors of oxazoline-substituted hydroxyfluorenes and hydroxylated benzoxazole were diversified by adding the π-conjugation. There is intriguing that the mechanism of diversified fluorescence colors induced by ESIPT. Here, the density functional theory(DFT) and time-dependent DFT(TDDFT)are advised to identify the effects of π-conjugation on ESIPT and photophysical properties. The stabilized geometrical configurations, frontier molecular orbitals(FMOs) isosurfaces, and O–H stretching vibration frequency analysis demonstrate that PT processes are more active in S1state. Constructing the minimum energy pathways of ESIPT processes, we find that the calculated peak of enol and keto fluorescence of naphthoxazole(NO–OH) is distinctly bathochromic-shift relative to the oxazoline-substituted hydroxyfluorenes(Oxa–OH) configuration when adding π-conjugation-substitution, and it means that π-conjugation-substitution can diversify the fluorescence color. We hope our studies can establish new channels to devise the ESIPT-based molecules.展开更多
Time-dependent density-functional theory(TDDFT)has been successfully applied to predict excited-state properties of isolated and periodic systems.However,it cannot address a system coupled to an environment or whose n...Time-dependent density-functional theory(TDDFT)has been successfully applied to predict excited-state properties of isolated and periodic systems.However,it cannot address a system coupled to an environment or whose number of electrons is not conserved.To tackle these problems,TDDFT needs to be extended to accommodate open systems.This paper provides a comprehensive account of the recent developments of TDDFT for open systems(TDDFT-OS),including both theoretical and practical aspects.The practicality and accuracy of a latest TDDFT-OS method is demonstrated with two numerical examples:the time-dependent electron transport through a series of quasi-one-dimensional atomic chains,and the real-time electronic dynamics on a two-dimensional graphene surface.The advancement of TDDFT-OS may lead to promising applications in various fields of chemistry,including energy conversion and heterogeneous catalysis.展开更多
基金supported by the National Natural Science Foundation of China(12126318,12126302).
文摘This paper develops a generalized scalar auxiliary variable(SAV)method for the time-dependent Ginzburg-Landau equations.The backward Euler method is used for discretizing the temporal derivative of the time-dependent Ginzburg-Landau equations.In this method,the system is decoupled and linearized to avoid solving the non-linear equation at each step.The theoretical analysis proves that the generalized SAV method can preserve the maximum bound principle and energy stability,and this is confirmed by the numerical result,and also shows that the numerical algorithm is stable.
文摘We consider a five-dimensional Minkowski space with two time dimensions characterized by distinct speeds of causality and three space dimensions. Formulas for relativistic coordinate and velocity transformations are derived, leading to a new expression for the speed limit. Extending the ideas of Einstein’s Theory of Special Relativity, concepts of five-velocity and five-momenta are introduced. We get a new formula for the rest energy of a massive object. Based on a non-relativistic limit, a two-time dependent Schrödinger-like equation for infinite square-well potential is developed and solved. The extra time dimension is compactified on a closed loop topology with a period matching the Planck time. It generates interference of additional quantum states with an ultra-small period of oscillation. Some cosmological implications of the concept of four-dimensional versus five-dimensional masses are briefly discussed, too.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11074176 and 10976019)the Research Fund for the Doctoral Program of Higher Education of China (Grant No.20100181110080)
文摘We report theoretical studies on the plasmon resonances in linear Au atomic chains by using ab initio time- dependent density functional theory. The dipole responses are investigated each as a function of chain length. They converge into a single resonance in the longitudinal mode but split into two transverse modes. As the chain length increases, the longitudinal plasmon mode is redshifted in energy while the transverse modes shift in the opposite direction (blueshifts). In addition, the energy gap between the two transverse modes reduces with chain length increasing. We find that there are unique characteristics, different from those of other metallic chains. These characteristics are crucial to atomic-scale engineering of single-molecule sensing, optical spectroscopy, and so on.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60601004,60801029,10876005,and60931001)
文摘This paper presents a three-dimensional time-dependent nonlinear theory of helix traveling wave tubes for beam- wave interaction. The radio frequency electromagnetic fields are represented as the superposition of azimuthally sym- metric waves in a vacuum sheath helix. Coupling impedance is introduced to the electromagnetic field equations' stimulating sources, which makes the theory easier and more flexible to realize. The space charge fields are calculated by electron beam space-charge waves expressed as the superposition solutions of Helmholtz equations. The focusing forces due to either a solenoidal field or a periodic permanent magnetic field is also included. The dynamical equations of electrons are Lorentz equations associating with electromagnetic fields, focusing fields and space-charge fields. The numerically simulated results of a tube are presented.
基金Project supported by the National Basic Research Program of China(Grant No.2013CB922204)the National Natural Science Foundation of China(Grant Nos.11574115 and 11704146)the Natural Science Foundation of Jilin Province,China(Grant No.20150101063JC)
文摘Time-dependent density functional theory(TDDFT) method is used to investigate the details of the excited state intramolecular proton transfer(ESIPT) process and the mechanism for temperature effect on the Enol*/Keto*emission ratio for the Me2N-substited flavonoid(MNF) compound. The geometric structures of the S0 and S1 states are denoted as the Enol, Enol*, and Keto*. In addition, the absorption and fluorescence peaks are also calculated. It is noted that the calculated large Stokes shift is in good agreement with the experimental result. Furthermore, our results confirm that the ESIPT process happens upon photoexcitation, which is distinctly monitored by the formation and disappearance of the characteristic peaks of infrared(IR) spectra involved in the proton transfer and in the potential energy curves. Besides, the calculations of highest occupied molecular orbital(HOMO) and lowest unoccupied molecular orbital(LUMO) reveal that the electronegativity change of proton acceptor due to the intramolecular charge redistribution in the S1 state induces the ESIPT. Moreover, the thermodynamic calculation for the MNF shows that the Enol*/Keto*emission ratio decreasing with temperature increasing arises from the barrier lowering of ESIPT.
基金The project was supported by the Scientific Research Fund of Hunan Provincial Education Department (No. 05A002)the Prominent Mid-youth Science and Technology Foundation of Hunan Province (No. 04JJ1010)
文摘Electronic properties, such as HOMO and LUMO energies, band gaps, ionization potential (IP) and electron affinity (EA) of 2,7- and 3,6-1inked carbazole trimers, two conjugated oligomcrs with different linkages of carbazole, were studicd by the density functional theory with Becke-Lee-Young-Parr composite exchange correlation functional (B3LYP). The absorption spectra of these compounds were also investigated by time-dependent density functional theory (TD-DFT) with 6-3 IG* basis set. The calculated results indicated that the HOMO and LUMO of the 2,7- and 3,6-1inked carbazole trimers are both slightly destabilized on going from methyl substitution to sec-butyl substitution. Both IP and EA exhibit their good hole-transporting but poor electronaccepting ability. The presence of alkyl groups on the nitrogen atoms does not affect the intra-chain electronic delocalization along the molecular frame. Thus no significant effect on the band gap and absorption spectra of compounds has been found.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.12372210 and 11972298).
文摘The macroscopic electromagnetic properties of type-II superconductors are mainly influenced by the behavior of micro-scopic superconducting flux quantum units.Time-dependent Ginzburg-Landau(TDGL)theory is a well-known tool for describing and examining both the statics and dynamics of these superconducting entities.It have been instrumental in replicating and elucidat-ing numerous experimental results over the past decades.This paper provides a comprehensive overview of the progress in TDGL simulations,focusing on three key aspects of superconductor applications.We delve first into vortex rectification in supercon-ductors described within the TDGL framework,specifically highlighting the achievement of superconducting diode effect through asymmetric pinning landscapes and the reversible manipulation of vortex ratchets with dynamic pinning landscapes.In terms of the achievements of TDGL simulations concerning the critical current density of superconductors,we emphasize particularly on the optimization of pinning sites,including vortex pinning and dynamics in polycrystalline Nb3Sn with grain boundaries.In the third aspect,we concentrate on numerical modeling of vortex penetration and dynamics in superconducting radio-frequency cavities,including a discussion on superconductor-insulator-superconductor multilayer structures.Finally,we present key findings,insights,and perspectives derived from the discussed simulations.
文摘Wellbore stability is a key to have a successful drilling operation.Induced stresses are the main factors affecting wellbore instability and associated problems in drilling operations.These stresses are significantly impacted by pore pressure variation and thermal stresses in the field.In order to address wellbore instability problems,it is important to investigate the mechanisms of rockefluid interaction with respect to thermal and mechanical aspects.In order to understand the induced stresses,different mathematical models have been developed.In this study,the field equations governing the problem have been derived based on the thermo-poroelastic theory and solved analytically in Laplace domain.The results are transferred to time domain using Fourier inverse method.Finite difference method is also utilized to validate the results.Pore pressure and temperature distributions around the wellbore have been focused and simulated.Next,induced radial and tangential stresses for different cases of cooling and heating of formation are compared.In addition,the differences between thermo-poroelastic and poroelastic models in situation of permeable and impermeable wellbores are described.It is observed that cooling and pore pressure distribution reinforce the induced radial stress.Whereas cooling can be a tool to control and reduce tangential stress induced due to invasion of drilling fluid.In the next step,safe mud window is obtained using Mohr-Coulomb,Mogi-Coulomb,and modified Lade failure criteria for different inclinations.Temperature and pore pressure distributions do not change the minimum allowable wellbore pressure significantly.However,upper limit of mud window is sensitive to induced stresses and it seems vital to consider changes in temperature and pore pressure to avoid any failures.The widest and narrowest mud windows are proposed by modified Lade and Mohr-Coulomb failure criteria,respectively.
基金supported by Fund from the Algerian Ministry of Higher Education and Scientific Research(Grant No.CNEPRU/D01220120010)the Basic Science Research Program of the year 2015 through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(Grant No.NRF-2013R1A1A2062907)
文摘The relationship between quantum mechanics and classical mechanics is investigated by taking a Gaussian-type wave packet as a solution of the Schr o¨dinger equation for the Caldirola–Kanai oscillator driven by a sinusoidal force. For this time-dependent system, quantum properties are studied by using the invariant theory of Lewis and Riesenfeld. In particular,we analyze time behaviors of quantum expectation values of position and momentum variables and compare them to those of the counterpart classical ones. Based on this, we check whether the Ehrenfest theorem which was originally developed in static quantum systems can be extended to such time-varying systems without problems.
基金supported by the National Natural Science Foundation of China(Grant No.11374133)the Taishan Scholars Project of Shandong Province,China(Grant No.ts2015110055)
文摘The photodetachment dynamics of H^- ion in a harmonic potential plus an oscillating electric field is studied using the time-dependent closed orbit theory. An analytical formula for calculating the photodetachment cross section of this system is put forward. It is found that the photodetachment cross section of this system is nearly unaffected for the weak oscillating electric field strength, but oscillates complicatedly when the oscillating electric field strength turns strong. In addition, the frequency of the harmonic potential and the oscillating electric field (the frequency of the harmonic potential and the frequency of the oscillating electric field are the same in the paper, unless otherwise stated.) can also affect the photodetachment dynamics of this system. With the increase of the frequency in the harmonic potential and the oscillating electric field, the number of the closed orbits for the detached electrons increased, which makes the oscillatory structure in the photodetachment cross section much more complex. Our study presents an intuitive understanding of the photodetachment dynamics driven by a harmonic potential plus an oscillating electric field from a space and time dependent viewpoint. This study is very useful in guiding the future experimental research for the photodetachment dynamics in the electric field both changing with space and time.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11074176 and 10976019) and the Doctoral Program of Higher Education of China (Grant No. 20100181110080).
文摘By using first-principles simulations based on time-dependent density functional theory, the chemical reaction of an HCl molecule encapsulated in C60 induced by femtosecond laser pulses is observed. The H atom starts to leave the Cl atom and is reflected by the C60 wall. The coherent nuclear dynamic behaviors of bond breakage and recombination of the HCl molecule occurring in both polarized parallel and perpendicular to the H-Cl bond axis are investigated. The radial oscillation is also found in the two polarization directions of the laser pulse. The relaxation time of the H-Cl bond lengths in transverse polarization is slow in comparison with that in longitudinal polarization. Those results are important for studying the dynamics of the chemical bond at an atomic level.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2020YFA0211300 and 2021YFA1201500)the National Natural Science Foundation of China(Grant Nos.U22A6005,92150110,12074237,and 12304426)+2 种基金the Natural Science Foundation of Shaanxi Province,China(Grant No.2024JC-JCQN-07)the Fundamental Science Foundation of Shaanxi Province,China(Grant No.22JSZ010)the Fundamental Research Funds for Central Universities(Grant Nos.GK202201012 and GK202308001).
文摘Alloy nanostructures supporting localized surface plasmon resonances has been widely used as efficient photocatalysts,but the microscopic mechanism of alloy compositions enhancing the catalytic efficiency is still unclear.By using time-dependent density functional theory(TDDFT),we analyze the real-time reaction processes of plasmon-mediated H_(2) splitting on linear Ag-Au alloy chains when exposed to femtosecond laser pulses.It is found that H_(2) splitting rate depends on the position and proportion of Au atoms in alloy chains,which indicates that specially designed Ag-Au alloy is more likely to induce the reaction than pure Ag chain.Especially,more electrons directly transfer from the alloy chain to the anti-bonding state of H_(2),thereby accelerating the H_(2) splitting reaction.These results establish a theoretical foundation for comprehending the microscopic mechanism of plasmon-induced chemical reaction on the alloy nanostructures.
基金Project supported by the National Key R&D Program of China (Grant Nos.2020YFA0211300 and 2021YFA1201500)the National Natural Science Foundation of China (Grant Nos.U22A6005,92150110,12074237,and 12304426)+2 种基金the Natural Science Foundation of Shaanxi Province (Grant No.2024JC-JCQN-07)the Fundamental Science Foundation of Shaanxi (Grant No.22JSZ010)the Fundamental Research Funds for Central Universities (Grant Nos.GK202201012 and GK202308001)。
文摘The plasmon-induced nonlinear response has attracted great attention in micro-nano optics and optoelectronics applications,yet the underlying microscopic mechanism remains elusive.In this study,the nonlinear response of gold nanoclusters when exposed to a femtosecond laser pulse was investigated using time-dependent density functional theory.It was observed that the third-order tunneling current was augmented in plasmonic dimers,owing to a greater number of electrons in the dimer being excited from occupied to unoccupied states.These findings provide profound theoretical insights and enable the realization of accurate regulation and control of nonlinear effects induced by plasmons at the atomic level.
基金Supported by National Natural Science Foundation of China(11201415,11571159)Program for New Century Excellent Talents in Fujian Province University(JA14191)
文摘In this paper, we prove the existence of global classical solutions to time-dependent Ginzburg-Landau(TDGL) equations. By the properties of Besov and Sobolev spaces, together with the energy method, we establish the global existence and uniqueness of classical solutions to the initial boundary value problem for time-dependent Ginzburg-Landau equations.
基金the National Natural Science Foundation of China(Grant Nos.11905160 and 11635003)the 333'project of Jiangsu Province(Grant No.BRA2020327)the Science Foundation of Wuxi Institute of Technology(Grant No.ZK201903).
文摘To investigate the collision processes of proton with the water dimer(H_(2)O)_(2)at 50 e V,the time-dependent density functional theory coupled with molecular dynamics nonadiabatically is applied.Six specific collision orientations with various impact parameters are considered.The reaction channels,the mass distribution and the fragmentation mass spectrum are explored.Among all launched samples,the probability of the channel of non-charge transfer scattering and charge transfer scattering is about 80%,hinting that the probability of fragmentation is about 20%.The reaction channel of proton exchange process 2 is taken as an example to exhibit the detailed microscopic dynamics of the collision process by inspecting the positions,the respective distance,the number of loss of electrons and the evolution of the electron density.The study of the mass distribution and the fragmentation mass spectrum shows that among all possible fragments,the fragment with mass 36 has the highest relative abundance of 65%.The relative abundances of fragments with masses 1,35,and 34are 20%,13%,and 1.5%,respectively.For the total electron capture cross section,the present calculations agree with the available measurements and calculations over the energy range from 50 e V to 12 ke V.
文摘The origins of superconductivity and pairing symmetry of order parameters are still controversial problems for FeSe thin films up to date.Under the Neumann boundary conditions,the electromagnetic properties of this system are investigated using the two-band Ginzburg-Landau theory.We calculate the temperature dependence of upper critical field in arbitrary direction and critical supercurrent density through the FeSe film.It is revealed that the normalized upper critical field is independent of the film thickness and all of our theoretical results are in accordance with the experimental data.These thus strongly indicate the existence of two-gap s-wave superconductivity in this material.
基金the National Natural Science Foundation of China(Grant Nos.12274054 and 12074054)the Fundamental Research Funds for the Central Universities(Grant No.DUT21LK06).
文摘Relationship of plasmonic properties of multiple clusters to molecular interactions and properties of a single cluster or molecule have become increasingly important due to the continuous emergence of molecular and cluster devices or systems.A hybrid phenomenon similar to plasmonic nanoparticle hybridization exists between two molecules with plasmon excitation modes.We use linear-response time-dependent density functional theory,real-time propagation time-dependent density functional theory,the plasmonicity index,and transition contribution maps(TCMs)to identify the plasmon excitation modes for the linear polyenes octatetraene with–OH and–NH_(2)groups and analyze the hybridization characteristics using charge transitions.The results show that molecular plasmon hybridization exists when the two molecules are coupled.The TCM analysis shows that the plasmon modes and hybridization result from collective and single-particle excitation.The plasmon mode is stronger,and the individual properties of the molecules are maintained after coupling when there is extra charge depose in the molecules because the electrons are moving in the molecules.This study provides new insights into the molecular plasmon hybridization of coupled molecules.
基金Project supported by the National Key Research and Development Program of China (Grant No.2019YFA0307700)the National Natural Science Foundation of China (Grant Nos.12204214,12074145,and 11627807)。
文摘High-order harmonic generation of the cyclo[18]carbon(C_(18) ) molecule under few-cycle circularly polarized laser pulse is studied by time-dependent density functional theory. Compared with the harmonic emission of the ring molecule C_(6)H_(6) having similar ionization potential, the C_(18) molecule has higher efficiency and cutoff energy than C_(6)H_(6) with the same laser field parameters. Further researches indicate that the harmonic efficiency and cutoff energy of the C_(18) molecule increase gradually with the increase of the laser intensity of the driving laser or decrease of the wavelength, both are larger than those of the C_(6)H_(6) molecule. Through the analysis of the time-dependent evolution of the electronic wave packets, it is also found that the higher efficiency of harmonic generation can be attributed to the larger spatial scale of the C_(18) molecule,which leads to a greater chance for the ionized electrons from one atom to recombine with others of the parent molecule.Selecting the suitable driving laser pulse, it is demonstrated that high-order harmonic generation in the C_(18) molecule has a wide range of applications in producing circularly polarized isolated attosecond pulse.
基金supported by the National Natural Science Foundation of China (Grant No. 11974152)the Shenyang High level Innovative Talents Program (Grant No. RC200565)+1 种基金the Science program of Liaoning Provincial Department of Education (Grant No. LJKZ0097)the Intercollegiate cooperation project of colleges and universities of Liaoning Provincial Department of Education。
文摘Excited-state intramolecular proton transfer(ESIPT) molecules are broadly applied to UV absorbers, fluorescence sensing, and lighting materials. In previous work, the fluorescence colors of oxazoline-substituted hydroxyfluorenes and hydroxylated benzoxazole were diversified by adding the π-conjugation. There is intriguing that the mechanism of diversified fluorescence colors induced by ESIPT. Here, the density functional theory(DFT) and time-dependent DFT(TDDFT)are advised to identify the effects of π-conjugation on ESIPT and photophysical properties. The stabilized geometrical configurations, frontier molecular orbitals(FMOs) isosurfaces, and O–H stretching vibration frequency analysis demonstrate that PT processes are more active in S1state. Constructing the minimum energy pathways of ESIPT processes, we find that the calculated peak of enol and keto fluorescence of naphthoxazole(NO–OH) is distinctly bathochromic-shift relative to the oxazoline-substituted hydroxyfluorenes(Oxa–OH) configuration when adding π-conjugation-substitution, and it means that π-conjugation-substitution can diversify the fluorescence color. We hope our studies can establish new channels to devise the ESIPT-based molecules.
基金supported by the National Natural Science Foundation of China(21103157,21233007,and 21322305)the Fundamental Research Funds for Central Universities(2340000034 and 2340000025)the Strategic Priority Research Program(B)of the CAS(XDB01020000)
文摘Time-dependent density-functional theory(TDDFT)has been successfully applied to predict excited-state properties of isolated and periodic systems.However,it cannot address a system coupled to an environment or whose number of electrons is not conserved.To tackle these problems,TDDFT needs to be extended to accommodate open systems.This paper provides a comprehensive account of the recent developments of TDDFT for open systems(TDDFT-OS),including both theoretical and practical aspects.The practicality and accuracy of a latest TDDFT-OS method is demonstrated with two numerical examples:the time-dependent electron transport through a series of quasi-one-dimensional atomic chains,and the real-time electronic dynamics on a two-dimensional graphene surface.The advancement of TDDFT-OS may lead to promising applications in various fields of chemistry,including energy conversion and heterogeneous catalysis.