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Internal Energy Distribution of Secondary Ions Under Argon and Bismuth Cluster Bombardments: “Soft” Versus “Hard” Desorption–Ionization Process
摘要： The emission/ionization process under massive argon cluster bombardment was investigated by measuring the internal energy distributions of a series of benzylpyridinium ions. Argon clusters with kinetic energies between 10 and 20 keV and cluster sizes ranging from 500 to 10,000 were used to establish the influence of their size, energy, and velocity on the internal energy distribution of the secondary ions. It is shown that the internal energy distribution of secondary ions principally depends on the energy per atom or the velocity of the cluster ion beam (E/n ∝ v2). Under low energy per atom (E/n ? 10 eV), the mean internal energy and fragmentation yield increase rapidly with the incident energy of individual constituents. Beyond 10 eV/atom impact (up to 40 eV/atom), the internal energy reaches a plateau and remains constant. Results were compared with those generated from bismuth cluster impacts for which the mean internal energies correspond well to the plateau values for argon clusters. However, a significant difference was found between argon and bismuth clusters concerning the damage or disappearance + impact cross section. A 20 times smaller disappearance cross section was measured under 20 keV Ar2000 + bombardment, thus quantitatively showing the low damage effect of large argon clusters compared to 25 keV Bi5 for almost the same molecular ion yield.
关键词： Bismuth cluster,Argon cluster,Internal energy,TOF-SIMS,Benzylpyridinium ion
更新于2025-09-04 15:30:14
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Performance of DFT for C <sub/>60</sub> Isomerization Energies: A Noticeable Exception to Jacob’s Ladder
摘要： The ability to accurately calculate relative energies of fullerenes is important in many areas of computational nanotechnology. Due to the large size of fullerenes, their relative energies cannot normally be calculated by means of high-level ab initio procedures, and therefore density functional theory (DFT) represents a cost-effective alternative. In an extensive benchmark study, we calculate the electronic energies of eight C60 isomers by means of the high-level G4(MP2) composite procedure. G4(MP2) isomerization energies span a wide range between 307.5–1074.0 kJ mol–1. We use this benchmark data to assess the performance of DFT, double-hybrid DFT (DHDFT), and MP2-based ab initio methods. Surprisingly, functionals from the second and third rungs of Jacob’s Ladder (i.e., GGA and meta-GGA functionals) significantly and systematically outperform hybrid and hybrid-meta-GGA functionals, which occupy higher rungs of Jacob’s Ladder. In addition, DHDFT functionals do not offer a substantial improvement over meta-GGA functionals, with respect to isomerization energies. Overall, the best performing functionals with mean absolute deviations (MADs) below 15.0 kJ mol–1 are (MADs given in parenthesis) the GGA N12 (14.7); meta-GGAs M06-L (10.6), M11-L (10.8), MN15-L (11.9), and TPSS-D3BJ (12.8); and the DHDFT functionals B2T-PLYP (9.3), mPW2-PLYP (9.8), B2K-PLYP (12.1), and B2GP-PLYP (12.3 kJ mol–1). In light of these results, we recommend the use of meta-GGA functionals for the calculation of fullerene isomerization energies. Finally, we show that inclusion of very small percentages of exact Hartree–Fock exchange (3–5%) slightly improves the performance of the GGA and meta-GGA functionals. However, their performance rapidly deteriorates with the inclusion of larger percentages of exact Hartree–Fock exchange.
关键词： Buckminsterfullerene,coupled cluster theory,G4(MP2) theory,density functional theory
更新于2025-09-04 15:30:14
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Thermodynamic conditions for cluster formation in supersaturated boundary layer during plasma spray-physical vapor deposition
摘要： Plasma spray-physical vapor deposition (PS-PVD) is used to produce columnar microstructure coatings for vapor materials under particular operating parameters. However, due to the particular conditions of PS-PVD, the state of vapor material transported in plasma jet is di?cult to predict by experimental method. Moreover, the properties of plasma jet changes sharply when the hot plasma jet approaches a relatively low temperature substrate. It is more di?cult to examine the behavior variation of vapor material by experiment. In this work, the thermodynamic condition for state variation of the vapor material along with methods to change this condition were studied. The distribution of plasma temperature near the substrate surface was obtained through simulation and the vapor pressure of vapor materials was calculated by the obtained temperature distribution. The supersaturated boundary layer was obtained from the distribution of the vapor pressure and partial pressure of the vapor atoms. The environment of this supersaturated boundary layer agreed with the thermodynamic conditions of the state variation of vapor materials. Further, this layer could be varied by changing the spraying distance and powder feed rate, thus allowing further control of the state variation of vapor materials. For PS-PVD process, especially for the deposition of columnar coating, it is very important to understand the properties of boundary layer and condensation conditions of vapor materials; this study provides the basis for future research on the transport of materials in the boundary layer.
关键词： Thermodynamic condition,Cluster,PS-PVD,Supersaturated boundary layer
更新于2025-09-04 15:30:14
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Atomic structure of a fluorescent Ag <sub/>8</sub> cluster templated by a multi-stranded DNA scaffold
摘要： Multinuclear silver clusters encapsulated by DNA exhibit size-tunable emission spectra and rich photophysics, but their atomic organization is poorly understood. Herein, we describe the structure of one such hybrid chromophore, a green-emitting Ag8 cluster arranged in a Big Dipper shape bound to the oligonucleotide A2C4. Three 3’ cytosine metallo-base pairs stabilize a parallel A-form-like duplex with a 5’ adenine-rich pocket, which binds a metallic, trapezoidal-shaped Ag5 moiety via Ag-N bonds to endo- and exo-cyclic nitrogens of cytosine and adenine. The unique DNA configuration, constrained coordination environment, and templated Ag8 cluster arrangement highlight the reciprocity between the silvers and DNA in adopting this structure. These first atomic details of a DNA-encapsulated Ag cluster fluorophore illuminate many aspects of biological assembly, nanoscience, and medical imaging.
关键词： crystallography,photophysics,silver,crystals,DNA,materials,nanocluster,nanomaterials,emissive cluster
更新于2025-09-04 15:30:14
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[IEEE 2018 25th IEEE International Conference on Image Processing (ICIP) - Athens, Greece (2018.10.7-2018.10.10)] 2018 25th IEEE International Conference on Image Processing (ICIP) - Hierarchical Palette Extraction Based on Local Distinctiveness and Cluster Validation for Image Recoloring
摘要： Palette-based image recoloring is one of the popular color manipulation methods by transforming dominant scene colors into corresponding user-specific colors intuitively. Because conventional palette extraction methods are based only on global color distribution, they cannot deal with local distinctive colors, which can cause not only the degraded result of image recoloring, but also the limitation of user selection. In this paper, we propose a new palette extraction method by iterative palette partitioning based on cluster validation. To find candidate colors for palette partitioning, we compute patch uniformity for local patches. For image recoloring with extracted palette, we use a statistics-based color transfer method by considering the pixel-wise weight from palette colors. In the experiments, our automatic or user-specific palette extraction shows more plausible palette representation than previous methods. Furthermore, image recoloring results show the effectiveness of the proposed method in terms of quality of color transfer and user experience.
关键词： Cluster validation,Local distinctiveness,Palette extraction,Color transfer,Image recoloring
更新于2025-09-04 15:30:14
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Optical Simulations of Self-assembly Relevant Gold Aggregates: A Comparative Study
摘要： In this study, visible light extinction spectra of different gold nanoparticle assemblies were simulated using boundary element method (BEM) in order to investigate the optical properties of structures which determine the experimentally measured spectra during the self-assembly of the particles. Numerous different optically dominant particle arrangements can evolve depending on the underlying physicochemical mechanism of the clustering process itself: one-dimensional chains, two-dimensional arrays or three-dimensional clusters can be formed in the solutions or at interfaces. Experimentally the aggregation or clustering of gold nanoparticles can be conveniently followed by spectroscopic techniques due to the plasmon coupling related profound effect of particle aggregation on the visible extinction spectrum. However, the measured spectra usually contain the optical response of various aggregate structures. Additionally, small changes of the interparticle distance can have a significant impact on the frequency of the coupled mode. In order to assess the contribution of the different structures to the experimentally measurable extinction spectra during particle clustering, different model structures (chains, array and 3D-cluster) have been simulated, where the distance between the particles was varied as well.
关键词： 3D cluster,boundary element method,2D heptamer,self-assembly,optical simulations,nanoparticle chains,gold nanoparticles
更新于2025-09-04 15:30:14
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Progress in metal organic cluster EUV photoresists
摘要： Most advanced microelectronic devices are made by using 193 nm immersion lithography systems, but it is difficult to follow the rapid development of semiconductors due to their approaching physical limits. Extreme ultraviolet (EUV) lithography which uses a shorter wavelength (i.e., 13.5 nm) light source can offer a way to print features under a 20 nm HP. EUV lithography requires photoresists that utilize EUV photons because photons generated by EUV exposure are fewer than photons generated by 193 nm light exposure. In this paper, our recent progress in metal oxide photoresist research will be discussed.
关键词： nanotechnology,lithography,semiconductor,EUV photoresists,metal organic cluster
更新于2025-09-04 15:30:14