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Theoretical study on nonlinear optical properties of N-(6-hydroxyhexyl)-5-nitroazophenyl carbazole
摘要： The first-, second- and third-order nonlinear optical properties of N-(6-hydroxyhexyl)-5-nitroazophenyl carbazole in gas phase employing sum-over-states (SOS) method have been calculated for the first time. The ground state molecular structure of N-(6-hydroxyhexyl)-5-nitroazophenyl carbazole was obtained by the geometrical optimizations based on the B3LYP/6-31+G(d) level. The energy of excited states and transition dipole moments between different excited states were obtained by using the time-dependent density functional theory (TDDFT) based on the CAM-B3LYP/Sadlej POL level. Charge transfer during electron excitation was analyzed based on hole and electron distributions. Our calculations showed that the N-(6-hydroxyhexyl)-5-nitroazophenyl carbazole has good nonlinear optical properties and its nonlinear optical properties arise from charge-transfer excitation and local excitation but charge transfer plays the leading role.
关键词： N-(6-hydroxyhexyl)-5-nitroazophenyl carbazole,the time-dependent density functional theory (TDDFT),charge transfer,sum-over-states (SOS) method,nonlinear optical properties
更新于2025-09-19 17:15:36
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Many-body States Description of Single-molecule Electroluminescence Driven by Scanning Tunneling Microscope
摘要： Electron transport and optical properties of a single molecule in contact with conductive materials have attracted considerable attention owing to their scientific importance and potential applications. With recent progresses of experimental techniques, especially by the virtue of scanning tunneling microscope (STM)-induced light emission, where the tunneling current of the STM is used as an atomic-scale source for induction of light emission from a single molecule, it becomes possible to investigate single-molecule properties at sub-nanometer spacial resolution. Despite extensive experimental studies, the microscopic mechanism of electronic excitation of a single molecule in STM-induced light emission is yet to be clarified. Here we present a formulation of single-molecule electroluminescence driven by electron transfer between a molecule and metal electrodes based on a many-body state representation of the molecule. The effects of intra-molecular Coulomb interaction on conductance and luminescence spectra are investigated using the nonequilibrium Hubbard Green's function technique combined with first-principles calculations. We compare simulation results with experimental data and find that the intra-molecular Coulomb interaction is crucial for reproducing recent experiments for a single phthalocyanine molecule. The developed theory provides a unified description of both electron-transport and optical properties of a single molecule in contact with metal electrodes driven out of equilibrium, and thereby it contributes to a microscopic understanding of optoelectronic conversion in single molecules on solid surfaces and in nanometer-scale junctions.
关键词： Single molecule luminescence,exciton formation,nonequilibrium Hubbard Green's function technique,time-dependent density functional theory (TDDFT),scanning tunneling microscope-induced light emission,Vibronic interaction
更新于2025-09-19 17:15:36
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Valence and core excitons in solids from velocity-gauge real-time TDDFT with range-separated hybrid functionals: An LCAO approach
摘要： An atomic-orbital basis set framework is presented for carrying out velocity-gauge real-time time-dependent density functional theory (TDDFT) simulations in periodic systems employing range-separated hybrid functionals. Linear optical response obtained from real-time propagation of the time-dependent Kohn-Sham equations including nonlocal exchange is considered in prototypical solid-state materials such as bulk Si, LiF and monolayer hexagonal-BN. Additionally core excitations in monolayer hexagonal-BN at the B and N K-edges are investigated and the role of long-range and short-range nonlocal exchange in capturing valence and core excitonic effects is discussed. Results obtained using this time-domain atomic orbital basis set framework are shown to be consistent with equivalent frequency-domain planewave results in the literature. The developments discussed lead to a time-domain generalized Kohn-Sham TDDFT implementation for the treatment of core and valence electron dynamics and light-matter interaction in periodic solid-state systems.
关键词： Core-level spectroscopy,TDDFT,Solid-state,Real-time,Excitons,Range-separated hybrid
更新于2025-09-19 17:15:36
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Reduced-scaling approach for CIS and time-dependent DFT calculations using hybrid functionals
摘要： An approximation is presented which can efficiently decrease the computational expenses of configuration interaction singles (CIS) and time-dependent density functional theory (TDDFT) methods employing hybrid functionals. The approach is the adaptation of the local density fitting scheme developed for Hartree–Fock (HF) calculations for excited states and reduces the quartic scaling of the methods to cubic. It can also be applied to related methods, such as the time-dependent HF and Tamm–Dancoff approximation TDDFT approaches. Our benchmark calculations show that, for molecules of 50 to 100 atoms, average speedups of 2 to 4 can be achieved for CIS and TDDFT calculations at the expense of negligible errors in the calculated excitation energies and oscillator strengths, but for bigger systems or molecules of localized electronic structure significantly larger speedups can be gained. We also demonstrate that the approximation enables excited-state calculations on a single processor even for molecules of 1000 atoms using basis sets augmented with diffuse functions including more than 17000 atomic orbitals.
关键词： hybrid functionals,local density fitting,excitation energies,TDDFT,reduced scaling,CIS
更新于2025-09-19 17:15:36
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Influence of the polarization of a multielectron atom in a strong laser field on high-order harmonic generation
摘要： We study the ionization and high-order harmonic generation (HHG) in argon by short linearly polarized laser pulses. We compare the populations of atomic orbitals and HHG spectra in a wide range of laser-pulse parameters, taking into account the dynamics of all orbitals based on the time-dependent density-functional theory (TDDFT) and only the most active orbital within the single-active electron (SAE) approximation. At high intensities of laser pulses, the atom polarization leads to suppression in the bound-state depletion due to the screening of the external field. The significant increase in the HHG yield is observed for the TDDFT calculations in comparison with the SAE calculations. The contribution of different orbitals in the TDDFT calculations of HHG spectra is discussed.
关键词： ionization,high-order harmonic generation,atom polarization,argon,TDDFT,laser pulses,SAE approximation
更新于2025-09-19 17:13:59
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Theoretical Study on the Use Cyano Acid Derivation as Electron Acceptors in Pelargonidin as Dye Compounds of Sensitized Solar Cells (DSSC)
摘要： The theoretical study of the use of cyano acid derivatives as electron acceptor groups in pelargonidin as a dye compound in sensitized solar cells (DSSC) was successfully carried out. Theoretical study was carried out with the purpose to determine the effect the addition of cyanoacrylic benzothiadiazole, cyanoacrylate, modification of cyanovinyl, and cyanocynamic as electron acceptors to the characteristics of pelargonidin as dye DSSC. The effect of modification is based on the parameters of bond length, spectra, molecular electron density, light harvesting efficiency (LHE), (VRP), and HOMO-LUMO energy. The molecular structure created using the Avogadro program, then optimized by DFT/TDDFT method using a base set 6.311G *. Based on the results of research on pelargonidin-benzothiadiazole cyanoacrylate is a better modification when compared with pelargonidin without modification or pelargonidin modified with other cyano acids. This modification is better modification based on parameters molecular electron density, HOMO-LUMO energy, (VRP), bond lengths, and spectra. Pelargonidin-benzothiadiazole cyanoacrylic electron density in LUMO conditions centred in benzothiadiazole cyanoacrylic, HOMO and LUMO energy of dye is -4.97856 eV & -2,56731 eV, VRP value 0.439, bond lengths 1.936 A, and spectra at wavelength 393-14 nm & 377-09 nm. Based on the light harvesting efficiency (LHE), pelargonidin without modification is the best modification with an LHE value 0.820.
关键词： Spectra,DFT,Pelargonidin,TDDFT,DSSC,VRP,Bond Length,Electron Acceptor,HOMO-LUMO,LHE
更新于2025-09-16 10:30:52
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Dye Aggregation, Photostructural Reorganization and Multiple Concurrent Dye···TiO <sub/>2</sub> Binding Modes in Dye-Sensitized Solar Cell Working Electrodes Containing Benzothiadiazole-Based Dye <b>RK-1</b>
摘要： Dye-sensitized solar cells (DSSCs) are widely considered as a promising contender for the next generation of photovoltaic devices. The light-harvesting component in the DSSCs, i.e., the sensitizers, are adsorbed onto the semiconductor layer to form the photoelectrode that absorbs solar energy and converts it into electrical power. The choice of dye has a profound impact on the DSSC performance. Thus, substantial research efforts have been devoted to the development and testing of a large variety of sensitizers during the past decades. We herein focus our attention on the metal-free benzothiadiazole-based dye 2-cyano-3-(4-(7-(5-(4-(diphenylamino)phenyl)-4-octylthiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)phenyl) acrylic acid (RK-1), which exhibits excellent power conversion efficiency and high stability. Simulations and experiments were combined to conduct a systematic study of its optical and structural properties. RK-1 shows a broad absorption band over the visible region and the formation of H aggregates in solution. Deprotonation of the cyanoacrylic acid group in RK-1 occurs upon dye adsorption onto TiO2. This induces a hypsochromic shift of the absorption band. The emission spectrum of RK-1 shows a broad band and a large Stokes shift (6949 cm-1), indicating the presence of several different structural reorganization processes during excitation. Time-dependent density functional theory (TD-DFT) calculations reveal that intramolecular charge transfer in RK-1 molecules should be predominantly attributed to the HOMO-LUMO transition. DFT modeling also reveals the involvement of cyano group in anchoring to TiO2 which makes the dye…TiO2 binding structure more stable. Fourier transform infra-red spectroscopy data prove that bridging bidentate (BB) and COO/CN (A2) binding modes co-exist in the RK-1···TiO2 interfacial structure.
关键词： DSSC dyes,RK-1,FTIR,DFT,TDDFT,binding mode
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing RECENT TRENDS IN PURE AND APPLIED MATHEMATICS - Vellore, India (13–15 December 2018)] RECENT TRENDS IN PURE AND APPLIED MATHEMATICS - Non-linear optical properties of carbazole based dyes modified with diverse spacer units for dye-sensitized solar cells: A first principle study
摘要： Density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations were performed for evaluating the photophysical and photochemical properties of a sequence of carbazole based metal-free organic dyes modified using different π-conjugation spacer units, such as thiopine, pyrrole, furan, thiazole and isoxazole. Moreover, the modified dyes were subjected to investigation towards their non-linear optical (NLO) features. The results revealed that dipole moment (μ), static polarizability (α), anisotropic polarizability (?α) and hyperpolarizability (first order (β) and second order (γ)) of modified dyes are considerably enhanced as a consequence of changing the spacer unit. Likewise, light harvesting efficiency and oscillator strength of the modified dyes are enhanced upon wavelength of absorption is red-shifted by influence of spacer moieties. We believe that our calculations provide a more profound physical perception on structural property relationship for carbazole based dyes and give a hint to create potential sensitizers for opto-electronic and dye-sensitized solar cell applications.
关键词： dyes,DFT,carbazole,TDDFT,non-linear optical properties,dye-sensitized solar cells
更新于2025-09-12 10:27:22
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Multi C–C/ C–N Coupled Light‐Emitting Aliphatic Terpolymers: N–H Functionalized Fluorophore‐Monomers and High‐Performance Applications
摘要： For circumventing the costly fluorescent labelling, nonconventional multifunctional intrinsically fluorescent aliphatic-terpolymers, i.e., 1, 2, 3, 4, and 5, were synthesized via C–C/ C–N coupled in situ protrusions of fluorophore-monomers in solution polymerization of two non-emissive monomers. These scalable terpolymers were suitable for sensing and high-performance exclusion of Cu(II), logic-function, and bioimaging. The structures of terpolymers, fluorescent monomers, aggregation-induced enhanced emissions, bioimaging abilities, and the superadsorption were understood using 1H/ 13C NMR, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, atomic absorption spectroscopy, thermogravimetric analysis, high-resolution transmission electron microscopy, dynamic light scattering, electron paramagnetic resonance spectroscopy, solid-state fluorescence, fluorescence imaging, and fluorescence lifetime, along with isotherms, kinetics, and thermodynamic studies. The geometries and electronic structures of fluorophores and absorption-emission properties of terpolymers were examined using density functional theory, time-dependent DFT, and natural transition orbital analyses. For 1, 2, and 5, the limit of detection values were 1.03 × 10?7, 1.65 × 10?7, and 1.77 × 10?7 M, respectively. The maximum adsorption capacities were 1575.21, 1433.70, and 1472.21 mg g?1 for 1, 2, and 5, respectively.
关键词： aliphatic,aggregation-induced enhanced emissions,light-emitting,logic-gates,superadsorption,Nonconventional,bioimaging,Cu(II)-sensors,DFT-TDDFT-NTO,terpolymers
更新于2025-09-11 14:15:04
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Rational design of visible light panchromatic absorption laser dye molecules: The first principle study
摘要： Laser dye molecules play an important role in tunable lasers due to enhancing the laser radiation intensity and increasing the laser adjustable range. The broad spectral bandwidth and visible light absorption allows for the evaluation of multiple fluorescence quenching mechanisms such as excition formation, photoinduced electron transfer, and excited-state proton transfer. A series of organic dye molecules (LD1-4、LA2-5、LU1-5、LV1-4、LI1-4) consisting of simple electron donor (D), conjugated bridge (π) and electron acceptor (A) units were designed using first-principles calculations in order to evaluate their potential for applications in tunable lasers. Furthermore, the optical and electronic properties of the dye molecules are analyzed in detail using density functional theory (DFT) and time-dependent density functional theory (TDDFT), including spectral parameters, energy levels and orbital contributions of organic dye molecules. The results indicate that LI1-3 show high molar extinction coefficient, visible light full color absorption and obvious red-shifted compared to the experimentally synthesized dye LA3. In particular, the newly designed LI3 exhibits not only a 190 nm red-shifted and a higher molar extinction coefficient with an increment of 19%, but also has an extremely broad absorption spectrum covering entire visible absorption spectrum from 380 to 750 nm compared to LD1. We also find that the dyes with dithiophene groups and naphthalene group as the electron donors are better absorption spectrum than dyes with double bond group and benzene group. These calculated results will hopefully contribute to the further development of novel laser dye molecules and further provide scientific support and theoretical guidance for subsequent related research.
关键词： Absorption spectra,Laser dye,DFT/TDDFT,Panchromatic absorption
更新于2025-09-11 14:15:04