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Application of Karpman-Maslov-Solov’ev soliton perturbation theory to systems with distributed gain or losses
摘要： We analyze the most important ideas of the Karpman-Maslov-Solov’ev soliton perturbation theory, and based on it, we solve analytically the long-standing problem of the Schr?dinger soliton interactions in the systems with distributed losses or gain. Our analytical results do give a quite good qualitative and quantitative check of the numerical results known so far. Unexpected and nontrivial result consists in the fact that the relative soliton separation depends on the accumulated (integrated) losses or gain.
关键词： Karpman-Maslov-Solov’ev soliton perturbation theory,Distributed losses or gain,Soliton interactions
更新于2025-09-23 15:23:52
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Photoelectron ejection by electromagnetic wave
摘要： Albert Einstein has explained photoelectric effect by corpuscle concept of light. Few phenomena are ambiguous in the explanation. The authors have explained photoelectric effect based on recent reported electromagnetic wave theory. The theoretical explanations of this works are covered all phenomena of the photoelectric effect such as the cause of electron ejection, kinetic energy of the photoelectron, the value of number of the photoelectron in the photocurrent, clear concept of ejection direction, initial ejection time, ejection as flog, frequency and intensity dependence, cutoff frequency and work function. The frequency and intensity dependence have been observed experimentally. The experimental observations show similar results of the theoretical explanation i.e. the kinetic energy of the photoelectron is proportional to both the intensity and frequency of light. The works may help to explain other photonic natures by wave theory of light.
关键词： Photoelectric Effect,Electromagnetic wave theory,Cutoff frequency
更新于2025-09-23 15:23:52
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Optimizing the conductance switching performance in photoswitchable dimethyldihydropyrene/cyclophanediene single-molecule junctions
摘要： Designing molecular switches with high stability and performance is still a great challenge in the field of molecular electronics. For this aim, key factors influencing the charge transport properties of molecular devices require to be carefully addressed. Here, by using the nonequilibrium Green’s function method in combination with the density functional theory, effect of bridging manner (i.e., linkage sites) for dimethyldihydropyrene (DHP)/cyclophanediene (CPD) photoswitchable molecule sandwiched between two Au(111) electrodes has been theoretically investigated. The computational results show that the fully conjugated DHP is more conductive than the less conjugated CPD, manifesting an evident switching effect. It is also found that the ON/OFF switching performance of DHP/CPD is dramatically modulated by the bridging manner. Further analysis attributes the switching feature to the different alignments of conducting HOMO with the Fermi energy for DHP and CPD. And it also reveals that local bond contributions to the electron transmission pathway are closely related to both the conjugation characteristics and bridging manner of the core molecule. This work suggests that the bridging manner of core molecule in single-molecule junction plays an essential role in determining the switching performance and should be carefully addressed in future design of molecular switches.
关键词： Single-molecule switch,Density functional theory,Nonequilibrium Green’s function method
更新于2025-09-23 15:23:52
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Anisotropic Circular Dichroism of Light-Harvesting Complex II in Oriented Lipid Bilayers: Theory Meets Experiment
摘要： Anisotropic circular dichroism (ACD) spectroscopy of macroscopically aligned molecules reveals additional information about their excited states that is lost in the CD of randomly-oriented solutions. ACD spectra of light-harvesting complex II (LHCII)—the main peripheral antenna of photosystem II in plants—in oriented lipid bilayers, were recorded from the far-UV to the visible wavelength region. The ACD spectra show a drastically enhanced magnitude and level of detail compared to the isotropic CD spectra, resolving a greater number of bands and weak optical transitions. Exciton calculations show that the spectral features in the chlorophyll Qy region are well reproduced by an existing Hamiltonian for LHCII, providing further evidence for the identity of energy sinks at chlorophylls a603 and a610 in the stromal layer and chlorophylls a604 and a613 in the luminal layer. We propose ACD spectroscopy to be a valuable tool linking the three-dimensional structure and the photophysical properties of pigment–protein complexes.
关键词： optical spectroscopy,photosynthetic complexes,model membranes,oriented CD,excitonic CD,exciton theory
更新于2025-09-23 15:23:52
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Theoretical Study on Adsorption Characteristics and Environmental Effects of Dimetridazole on TiO2 Surface
摘要： In this paper, the adsorption characteristics of dimetridazole on anatase TiO2(101) and (001) crystal surfaces has been studied by using density functional theory. Adsorption structures of dimetridazole on anatase TiO2(101) and (001) crystal surfaces have been optimized under vacuum, water, acidic and alkaline conditions, respectively. The optimum adsorption site, adsorption energy and the electronic structure of the stable adsorption model were calculated. By analyzing the optimal adsorption site, we found that the possibility of degradation of dimetridazole on the surface of TiO2 and reaction site of degradation were the opening ring of C-N bond on the imidazole ring. By comparing the adsorption characteristics of dimetridazole on two different crystal planes of TiO2 under acidic and alkaline conditions, we found that the adsorption wavelengths of electron transition between conduction bands and valence bands of dimetridazole on anatase TiO2(101) crystal plane are within the range of visible wavelength. The results show that TiO2(101) can effectively utilize visible light and catalyze the adsorption and degradation reaction of dimetridazole on TiO2(101) surface. Our results show that TiO2(101) crystal surface can effectively use visible light under acidic and alkaline conditions. Our conclusion can explain the experimental result that the use of visible light on TiO2(001) face is greatly affected by the environment.
关键词： Dimetridazole,Density functional theory,TiO2 Photocatalyst,Explanation
更新于2025-09-23 15:23:52
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Effect of acceptor moieties on static and dynamic first hyperpolarizability of azobenzene chromophores
摘要： The effect of acceptor on static and dynamic first hyperpolarizability, β, of trans- and cis-isomers of azochromophores AAB-DCV and AAB-TCV is studied. Calculations were performed by MP2 and DFT with three density functionals: M06-2X, CAM-B3LYP and ωB97X-D in gas phase and chloroform. Dynamic first hyperpolarizabilities were calculated by TD-DFT at 1.165 and 0.65 eV. The first hyperpolarizability values for trans-isomers are approximately three times greater than those for cis-isomer; solvent effect is essential comprising 2.7 and 3.2 times growth for static values for AAB-DCV and AAB-TCV, respectively, the corresponding dynamic estimations for βtot(2ω) being slightly smaller (2.2 and 2.6 times).
关键词： Dynamic characteristics,MP2,Azochromophore,Solvent effect,Acceptor effect,First hyperpolarizability,Density functional theory,TD-DFT
更新于2025-09-23 15:23:52
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Exploring approximate geometries of minimum energy conical intersections by TDDFT calculations
摘要： An approach is proposed to obtain approximate geometries for minimum energy conical intersections between the ground and first excited singlet electronic states (S0/S1-MECIs) using the time-dependent density functional theory (TDDFT). This approach uses the energy shift method to avoid discontinuities on TDDFT potential energy surfaces around conical intersections. It is shown numerically that the approximate S0/S1-MECIs of benzene and naphthalene obtained by this approach qualitatively reproduce the geometries and energies of the S0/S1-MECIs obtained by multireference theories. Moreover, the performance of the present approach when combined with an automated MECI searching method is examined through applications to benzene and naphthalene.
关键词： energy shift method,time dependent density functional theory,gradient projection,single component artificial force induced reaction,conical intersection,global reaction route mapping
更新于2025-09-23 15:23:52
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Acceptor levels of the carbon vacancy in 4 <i>H</i> -SiC: Combining Laplace deep level transient spectroscopy with density functional modeling
摘要： We provide direct evidence that the broad Z1/2 peak, commonly observed by conventional deep level transient spectroscopy in as-grown and at high concentrations in radiation damaged 4H-SiC, has two components, namely, Z1 and Z2, with activation energies for electron emissions of 0.59 and 0.67 eV, respectively. We assign these components to Z?1/2 + e? → Z?1/2 → Z?1/2 + 2e? transition sequences from negative-U ordered acceptor levels of carbon vacancy (V_C) defects at hexagonal/pseudo-cubic sites, respectively. By employing short filling pulses at lower temperatures, we were able to characterize the first acceptor level of V_C on both sub-lattice sites. Activation energies for electron emission of 0.48 and 0.41 eV were determined for Z1(?/0) and Z2(?/0) transitions, respectively. Based on trap filling kinetics and capture barrier calculations, we investigated the two-step transitions from neutral to doubly negatively charged Z1 and Z2. Positions of the first and second acceptor levels of V_C at both lattice sites, as well as (?/0) occupancy levels, were derived from the analysis of the emission and capture data.
关键词： density functional theory,acceptor levels,deep level transient spectroscopy,negative-U ordering,carbon vacancy,4H-SiC
更新于2025-09-23 15:23:52
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Scattering of electromagnetic waves by a perfect electromagnetic conductor half-screen
摘要： The diffraction of plane electromagnetic waves by a perfect electromagnetic conductor half-screen is investigated. The total geometrical optics fields are obtained by using the boundary conditions of a perfect electromagnetic conductor surface. A general relation is defined for the scattered fields in terms of waves by soft and hard surfaces. The total scattered field is derived by using this relation. Some numerical simulations are also given.
关键词： Perfect electromagnetic conductor,Geometric optics,Diffraction theory
更新于2025-09-23 15:23:52
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Cobalt doping-induced strong electromagnetic wave absorption in SiC nanowires
摘要： Understanding the electronic structure-property relationship in doped systems is a prerequisite to designing functional materials. We fabricated Co-doped SiC nanowires with different Co contents by a facile carbothermal reduction approach. The nanowires were characterized in terms of microstructure, electronic structure, and electromagnetic (EM) parameters to uncover the effect of Co dopants on enhancing the EM wave absorption ability. Microstructure analysis and density functional theory calculations verified that the doped Co species inhibited the formation of stacking faults and point defects and increased the conductivity of Co-doped SiC nanowires, which indicated the dominant role of conductivity in enhancing dielectric loss. The Co dopants also imparted the Co-doped SiC nanowires with distinct room-temperature ferromagnetic property, which led to enhanced magnetic loss and impedance matching. The induced synergism among SiC nanowires and Co dopants endowed Co-doped SiC nanowires with strong EM wave absorption ability. The minimum reflection loss of Co-doped SiC nanowires reaches (cid:1)50 dB, and the effective absorption bandwidth is 4.0 GHz with only 1.5 mm sample thickness. Thus, Co-doped SiC nanowires can be used as effective EM wave absorption materials. This study also provided a guideline for designing high-performance EM wave absorbers.
关键词： Dielectric loss,Doping,Density functional theory calculations,Electromagnetic wave absorption,Magnetic property
更新于2025-09-23 15:23:52