Search results for "clusters"
showing 10 items of 1274 documents
Stability, electronic structure, and optical properties of protected gold-doped silver Ag29−xAux (x = 0–5) nanoclusters
2017
In this work, we used density functional theory (DFT) and linear response time-dependent DFT (LR-TDDFT) to investigate the stability, electronic structure, and optical properties of Au-doped [Ag29-xAux(BDT)12(TPP)4]3- nanoclusters (BDT: 1,3-benzenedithiol; TPP triphenylphosphine) with x = 0-5. The aim of this work is to shed light on the most favorable doped structures by comparing our results with previously published experimental data. The calculated relative energies, ranging between 0.8 and 10 meV per atom, indicate that several doped Ag29-xAux nanoclusters are likely to co-exist at room temperature. However, only the Au-doped [Ag29-xAux(BDT)12(TPP)4]3- nanoclusters that have direct bon…
Unravelling the Intertwined Atomic and Bulk Nature of Localised Excitons by Attosecond Spectroscopy
2021
The electro-optical properties of most semiconductors and insulators of technological interest are dominated by the presence of electron-hole quasi-particles, called excitons. The manipulation of excitons in dielectrics has recently received great attention, with possible applications in different fields including optoelectronics and photonics. Here, we apply attosecond transient reflection spectroscopy in a sequential two-foci geometry and observe sub-femtosecond dynamics of a core-level exciton in bulk MgF2 single crystals. Furthermore, we access absolute phase delays, which allow for an unambiguous comparison with theoretical calculations. Our results show that excitons surprisingly exhi…
4,4'-[Thiophene-2,5-diylbis(ethyne-2,1-diyl)]dibenzonitrile
2008
In the solid state, the title compound, C(22)H(10)N(2)S, forms centrosymmetric dimers by pairs of non-classical C-H⋯S hydrogen bonds linking approximately coplanar mol-ecules. The benzene ring involved in this inter-action makes a dihedral angle of only 7.21 (16)° with the thio-phene ring, while the other benzene ring is twisted somewhat out of the plane, with a dihedral angle of 39.58 (9)°. The hydrogen-bonded dimers stack on top of each other with an inter-planar spacing of 3.44 Å. C-H⋯N hydrogen bonds link together stacks that run in approximately perpendicular directions. Each mol-ecule thus inter-acts with 12 adjacent mol-ecules, five of them approaching closer than the sum of the van …
Reaction of LiArMe6 (ArMe6ArMe6 = C6H3-2,6-(C6H2-2,4,6-Me3)2) with indium(I)chloride yields three m-terphenyl stabilized mixed-valent organoindium su…
2016
Indium(I)chloride reacts with LiArMe6 (ArMe6 = C6H3-2,6-(C6H2-2,4,6-Me3)2) in THF to give three new mixed-valent organoindium subhalides. While the 1:1 reaction of InCl with LiArMe6 yields the known metal-rich cluster In8(ArMe6)4 (1), the use of freshly prepared LiArMe6 led to incorporation of iodide, derived from the synthesis of LiArMe6, into the structures, to afford In4(ArMe6)4I2 (2) along with minor amounts of In3(ArMe6)3I2 (3). When the same reaction was performed in 4:3 stoichiometry, the mixed-halide compound In3(ArMe6)3ClI (4) was obtained. Further increasing the chloride:aryl ligand ratio resulted in the formation of the known mixed-halide species In4(ArMe6)4Cl2I2 that can also be…
C1,α-regularity for variational problems in the Heisenberg group
2017
We study the regularity of minima of scalar variational integrals of $p$-growth, $1<p<\infty$, in the Heisenberg group and prove the H\"older continuity of horizontal gradient of minima.
TRAIL acts synergistically with iron oxide nanocluster-mediated magneto- and photothermia
2019
International audience; Targeting TRAIL (Tumor necrosis factor (TNF)-Related Apoptosis-Inducing Ligand) receptors for cancer therapy remains challenging due to tumor cell resistance and poor preparations of TRAIL or its derivatives. Herein, to optimize its therapeutic use, TRAIL was grafted onto iron oxide nanoclusters (NCs) with the aim of increasing its pro-apoptotic potential through nanoparticle-mediated magnetic hyperthermia (MHT) or photothermia (PT). Methods: The nanovector, NC@TRAIL, was characterized in terms of size, grafting efficiency, and potential for MHT and PT. The therapeutic function was assessed on a TRAIL-resistant breast cancer cell line, MDA-MB-231, wild type (WT) or T…
Photoelectron emission experiments with ECR-driven multi-dipolar negative ion plasma source
2017
Photoelectron emission measurements have been performed using a 2.45 GHz ECR-driven multi-dipolar plasma source in a low pressure hydrogen discharge. Photoelectron currents induced by light emitted from ECR zone and H− production region are measured from Al, Cu, Mo, Ta, and stainless steel (SAE 304) surfaces as a function of microwave power and neutral hydrogen pressure. The total photoelectron current from the plasma chamber wall is estimated to reach values up to 1 A for 900 W of injected microwave power. It is concluded that the volumetric photon emission rate in wavelength range relevant for photoelectron emission is a few times higher in arc discharge. peerReviewed
VUV emission spectroscopy combined with H- density measurements in the ion source Prometheus I
2016
“Prometheus I” is a volume H− negative ion source, driven by a network of dipolar electron cyclotron resonance (ECR; 2.45 GHz) modules. The vacuum-ultraviolet (VUV) emission spectrum of low-temperature hydrogen plasmas may be related to molecular and atomic processes involved directly or indirectly in the production of negative ions. In this work, VUV spectroscopy has been performed in the above source, Prometheus I, both in the ECR zones and the bulk (far from ECR zones and surfaces) plasma. The acquired VUV spectra are correlated with the negative ion densities, as measured by means of laser photodetachment, and the possible mechanisms of negative ion production are considered. The well-e…
Kohn-Sham Decomposition in Real-Time Time-Dependent Density-Functional Theory An Efficient Tool for Analyzing Plasmonic Excitations
2017
The real-time-propagation formulation of time-dependent density-functional theory (RT-TDDFT) is an efficient method for modeling the optical response of molecules and nanoparticles. Compared to the widely adopted linear-response TDDFT approaches based on, e.g., the Casida equations, RT-TDDFT appears, however, lacking efficient analysis methods. This applies in particular to a decomposition of the response in the basis of the underlying single-electron states. In this work, we overcome this limitation by developing an analysis method for obtaining the Kohn-Sham electron-hole decomposition in RT-TDDFT. We demonstrate the equivalence between the developed method and the Casida approach by a be…
Self-Consistent Charge Density-Functional Tight-Binding Parametrization for Pt–Ru Alloys
2017
We present a self-consistent charge density-functional tight-binding (SCC-DFTB) parametrization for PtRu alloys, which is developed by employing a training set of alloy cluster energies and forces obtained from Kohn-Sham density-functional theory (DFT) calculations. Extensive simulations of a testing set of PtRu alloy nanoclusters show that this SCC-DFTB scheme is capable of capturing cluster formation energies with high accuracy relative to DFT calculations. The new SCC-DFTB parametrization is employed within a genetic algorithm to search for global minima of PtRu clusters in the range of 13-81 atoms and the emergence of Ru-core/Pt-shell structures at intermediate alloy compositions, consi…