- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Assessment of functionals for TDDFT calculations of one- and two-photon absorption properties of neutral and anionic fluorescent proteins chromophores
摘要： Performance of DFT functionals with different percentage of exact Hartree-Fock exchange energy (EX) is assessed for recovery of the CC2 reference one- (OPA) and two-photon absorption (TPA) spectra of fluorescent proteins chromophores in vacuo. The investigated DFT functionals, together with their EX contributions are: BLYP (0%), B3LYP (20%), B1LYP (25%), BHandHLYP (50%) and CAM-B3LYP (19% at short range and 65% at long range). Our test set consists of anionic and neutral chromophores as naturally occuring in the fluorescent proteins. For the first time, we compare TDDFT and CC2 methods for higher excited states, than the S1 state, exhibiting relatively large TPA intensity. Our TDDFT results for neutral chromophores reveal an increase of excitation energies as well as TPA and OPA intensities errors, compared to CC2-derived results, as the DFT functional contains less exact exchange. The long-range-corrected CAM-B3LYP functional performs the best, closely followed by BHandHLYP, while BLYP usually significantly underestimates all investigated spectral properties, hence being the worst in reproducing the reference CC2 results. The hybrid B3LYP and B1LYP functionals can be roughly placed in between. We propose that TDDFT may underestimate the TPA intensities for neutral chromophores of fluorescent proteins due to underestimated oscillator strengths between some excited states. In case of anionic chromophores, we find that B3LYP and B1LYP functionals overcome others in terms of reproducing CC2 excitation energies. On the other hand, however, TPA intensity is usually significantly underestimated and in this respect CAM-B3LYP functional seems to be again superior. In contrast to the case of neutral chromophores, it seems that large magnitude of excited-state dipole moment or change in dipole moment upon excitation may be the driving force behind high TPA transition moments.
关键词： fluorescent proteins chromophores,one-photon absorption,DFT functionals,two-photon absorption,TDDFT,CC2
更新于2025-09-23 15:21:21
-
<i>l</i> -Stercobilin-HCl and <i>d</i> -Urobilin-HCl. Analysis of Their Chiroptical and Conformational Properties by VCD, ECD, CPL Experiments and MD, DFT Calculations
摘要： Vibrational circular dichroism (VCD) and IR spectra of dichloromethane solutions of l-stercobilin and d-urobilin hydrochlorides have been recorded in the mid-IR region. The spectra are best interpreted by combining molecular dynamics (MD) calculations and DFT calculations within the QM/MM ONIOM-type framework, and the combined predicted results are better and more informative than the more standard analysis provided by DFT calculations. The same approach also sheds light on the Cotton effect sign inversion of room temperature versus low temperature electronic CD (ECD) spectra of the same compounds in methanol-glycerol solution. Finally, circularly polarized luminescence (CPL) spectra for l-stercobilin in chloroform solution provide information on the excited state geometry of this molecule.
关键词： Vibrational circular dichroism,electronic CD,molecular dynamics,IR spectra,QM/MM ONIOM-type framework,Cotton effect,circularly polarized luminescence,DFT calculations
更新于2025-09-23 15:21:21
-
[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - Expanding the Unambiguous Velocity Limitation of the Stepped-Carrier OFDM Radar Scheme
摘要： The main limitation for the practical implementation of OFDM radars is the required high sampling rate of AD/DA converters. It can be solved by using a stepped-carrier OFDM scheme. Thereby, the same range and Doppler resolution is obtained as for a standard OFDM scheme at the cost of a reduced unambiguously measurable velocity. This paper presents a method to determine the actual velocity even for targets that violate the unambiguous velocity limitation. It is based on characteristics of the DFT and it is suitable for scenes with few targets or if all targets have a similar velocity.
关键词： OFDM,radar,DFT,stepped carrier,frequency-agility,automotive
更新于2025-09-23 15:21:21
-
Synthesis, ellipsometry and non-linear optical features of substituted 1,3,5-triphenylpyrazolines
摘要： Ellipsometric and nonlinear optical properties of new, differently substituted, 1,3,5-triphenylpyrazolines dyes, were studied. Results of theoretical calculation within a framework of density functional theory (DFT) technique were verified by spectroscopic ellipsometry and optical second harmonic generation (SHG) experiment at fundamental laser wavelength 1064 nm. Absorption bands and complex refractive indices were determined. Principal role of 2-thienyl substituent for first order nonlinear optical properties was demonstrated.
关键词： pyrazolines,DFT method,Nonlinear optics,spectroscopic ellipsometry
更新于2025-09-23 15:21:21
-
Thermodynamic stability, half-metallic and optical nature of graphene-like Mn <sub/>2</sub> Zr <i>Z</i> ( <i>Z</i> = Ge, Si): <i>Ab initio</i> study
摘要： Half-metallic, optical and thermodynamic phase diagrams of two-dimensional Mn2ZrZ (Z = Ge, Si) have been calculated by density functional theory (DFT) framework with full-potential linear augmented plane-wave (FP-LAPW) method. The spin-polarized electronic computations show that these layers have metallic behavior with a spin polarization less than 100%. It is observed that with increasing thickness of the layers, both the thermodynamic and energy stabilities increased, and the graphene-like layers of Mn2ZrGe with a thickness of 7.6955 ?A and Mn2ZrSi with a thickness of 7.551 ?A are completely stable thermodynamically. The optical responses of Mn2ZrZ (Z = Ge, Si) have anisotropy at infrared region versus the optical direction and have high metallic nature in this optical range. The plasmonic frequencies have occurred after the visible edge and the refraction index becomes lower than one after the ultra-violet edge.
关键词： optical property,half-metal,thermodynamic phase diagram,DFT,Graphene-like Mn2ZrZ (Z = Ge, Si)
更新于2025-09-23 15:21:21
-
<i>(Invited)</i> Large-Scale DFT Study of Ge/Si 3D Nanoislands and Core-Shell Nanowires
摘要： Density functional theory (DFT) calculations have been playing important roles to clarify the structures of semiconductor surfaces at atomic scale. However, DFT studies of complex nanostructures are usually impossible because conventional DFT methods cannot treat large systems containing many thousands of atoms. In this paper, we survey our large scale DFT study on (i) the growth of Ge 3D nanostructure on Si(001) substrate and (ii) the atomic and electronic structures of Si/Ge or Ge/Si core-shell nanowires, using our linear-scaling DFT code CONQUEST. The code uses large-scale DFT techniques and has high efficiency on massively parallel computers. We demonstrate that CONQUEST can calculate the atomic positions of the realistic models of nanostructures observed in experiments and can clarify the unique electronic properties of these nano-structured materials.
关键词： nanoislands,CONQUEST,Ge/Si,DFT,core-shell nanowires
更新于2025-09-23 15:21:21
-
Photocatalytic removal of diclofenac by Ti doped BiOI microspheres under visible light irradiation: Kinetics, mechanism, and pathways
摘要： BiOI microspheres doped with different amounts of Ti were fabricated and used to remove diclofenac (DCF) from water under visible light irradiation. The fabricated photocatalysts were well characterized. Ti doped BiOI microspheres were found to exhibit higher photocatalytic activity towards DCF under visible light compared with BiOI. Ti doping broadened the band gap of BiOI, which leads to a more negative conduction band edge and a higher reducing activity of photo-generated electrons, thus facilitates ·O2? production during photocatalysis. Among all the fabricated Ti doped BiOI microspheres, TB450 exhibited the highest DCF photocatalytic removal efficiency. Specifically, 99.2% of DCF (C0 = 10 mg L?1) was removed by TB450 (250 mg L?1) at pH 5 within 90 min under visible light irradiation. Scavenger experiments indicated that active species including h+, ·O2? and H2O2 played important roles in the photocatalytic process. The degradation pathway of DCF was elucidated by theoretical density functional theory (DFT) and by-products identification through liquid chromatograph mass spectrometer (LC-MS) analysis. DCF degradation pathway mainly included hydroxylation and the cleavage of C\N bond. DFT calculation can well interpret the degradation mechanism and the sites of DCF molecule with high radical-attack Fukui index (f0) exhibit high reactivity. Acidic condition was found to facilitate the DCF photocatalytic removal. Due to strong photo-stability, Ti doped BiOI microspheres contained good visible-light-driven (VLD) photocatalytic removal efficiency for DCF in the fourth consecutive reused cycle. Ti doped BiOI microspheres can be employed as a cost-effective and high-efficient material to efficiently degrade emerging contaminants (e.g., pharmaceutical) from wastewaters under visible light conditions.
关键词： Ti doped BiOI microspheres,Photocatalysis,Diclofenac,Reuse,Degradation pathway,DFT calculation
更新于2025-09-23 15:21:21
-
Synthesis of Pyridazine Derivatives by Suzuki-Miyaura Cross-Coupling Reaction and Evaluation of Their Optical and Electronic Properties through Experimental and Theoretical Studies
摘要： A series of π-conjugated molecules, based on pyridazine and thiophene heterocycles 3a–e, were synthesized using commercially, or readily available, coupling components, through a palladium catalyzed Suzuki-Miyaura cross-coupling reaction. The electron-deficient pyridazine heterocycle was functionalized by a thiophene electron-rich heterocycle at position six, and different (hetero)aromatic moieties (phenyl, thienyl, furanyl) were functionalized with electron acceptor groups at position three. Density Functional Theory (DFT) calculations were carried out to obtain information on the conformation, electronic structure, electron distribution, dipolar moment, and molecular nonlinear response of the synthesized push-pull pyridazine derivatives. Hyper-Rayleigh scattering in 1,4-dioxane solutions, using a fundamental wavelength of 1064 nm, was used to evaluate their second-order nonlinear optical properties. The thienylpyridazine functionalized with the cyano-phenyl moiety exhibited the largest first hyperpolarizability (β = 175 × 10?30 esu, using the T convention) indicating its potential as a second harmonic generation (SHG) chromophore.
关键词： pyridazine,Density Functional Theory (DFT),Nonlinear optics (NLO),Second Harmonic Generators (SHG),Suzuki-Miyaura coupling
更新于2025-09-23 15:21:21
-
CH<sub>2</sub>O Adsorption on M (M = Li, Mg and Al) Atom Deposited ZnO Nano-Cage: DFT Study
摘要： The structural and electronic properties of Li, Mg and Al deposited ZnO nano-cages and their effects on the adsorption of formaldehyde molecule have been investigated using the density functional theory (DFT) computations. To understand the behavior of the adsorbed CH2O molecule on the ZnO nano-cage, results of DFT calculations of the M-deposited nano-cages (M=Li, Mg and Al), as well as complex systems consisting of the adsorbed CH2O molecule on M-deposited ZnO nano-cage were reported. The results presented include adsorption energies, bond lengths, electronic configurations, density of states and molecular orbitals. It was found that, the most energetically stable adsorption configurations of CH2O molecule on the bare ZnO leads to 12% dilation in C=O bond length of CH2O and 14% decrease in HOMO-LUMO gap of ZnO cluster. The most energetically stable adsorption configurations of CH2O molecule on Li, Mg and Al-deposited ZnO lead to 4%, 4% and 11% dilation in C=O bond length of CH2O and -0.66, -45 and , +66% change in HOMO-LUMO gap of ZnO nano cages, respectively. The interaction between CH2O with bare ZnO and M-deposited ZnO nano-cages is attributed to charge transfer mechanism. These results may be meaningful for CH2O degradation and detection.
关键词： ZnO,Adsorption,nanomaterials,Formaldehyde,DFT
更新于2025-09-23 15:21:21
-
Multimodal Approach for Rationalization and Quantification of Structural Disorder in Transition Al 2 O 3
摘要： Transition aluminas form a basis of important catalytic and catalytic support materials due to their unique surface acidity, high temperature structural stability, and their viability for synthesis as high surface area materials. The origin of transition aluminas attractive properties has been extensively studied in the past 50+ years, but despite this effort, there are number of structural, electronic and surface properties that remain poorly understood. The poor understanding stems mostly from the inadequate crystallographic description of transition alumina polymorphs of γ-Al2O3, δ-Al2O3, θ-Al2O3 that evolve as a continuum of metastable structures. This work focuses on rationalization and quantification of structural disorder in Boehmite derived transition aluminas by using a suite of complementary imaging, spectroscopy and quantum calculation techniques. Based on aberration corrected STEM HAADF imaging, it will be shown that the individual polymorphs of δ?Al2O3 and θ-Al2O3 accommodate a significant degree of structural disorder, which leads to loss of crystallographic periodicity. The complexity of this disorder can be rationalized as an atomic scale intergrowth of closely related crystallographic variants. As a part of this work, we present a crystallographic approach based on real space interpretation of projected atomic potential that enabled us to unambiguously derive Al3+ coordination in δ-Al2O3 and θ-Al2O3 from a series of low-index STEM HAADF images. This work lead to a full crystallographic description of the crystallographic variants belonging to δ-Al2O3 and θ-Al2O3 family. To quantify the heterogeneous microstructure of transition aluminas on statistically relevant bases, we employed novel approaches for characterization of structural disorder using XRD and NMR techniques. XRD is one of the most employed methods for crystallographic bulk characterization, but historically it has not been successfully used on transition alumina. It will be shown that the crystallographic polymorphs and their structural disorder can be quantified with the use of recursive algorithms as implemented in DIFFAX and TOPAS XRD simulation packages. To further validate the quantification of structural disordered in transition Al2O3, we also employed complementary NMR spectroscopy, combined with DFT NMR simulation methods. As a part of this talk, we also discuss results from DFT energetic calculations explaining how energetic degeneracy between the number of crystallographic variants leads to structural disorder in transition aluminas.
关键词： DFT,transition aluminas,structural disorder,NMR,XRD,STEM HAADF imaging
更新于2025-09-23 15:21:21