排序方式: 共有105条查询结果,搜索用时 15 毫秒
41.
Fock J Sørensen JK Lörtscher E Vosch T Martin CA Riel H Kilså K Bjørnholm T van der Zant H 《Physical chemistry chemical physics : PCCP》2011,13(32):14325-14332
We report on the vibrational fingerprint of single C(60) terminated molecules in a mechanically controlled break junction (MCBJ) setup using a novel statistical approach manipulating the junction mechanically to address different molecular configurations and to monitor the corresponding vibrational modes. In the IETS spectra, the vibrations of the anchoring C(60) dominate the spectra; thus information on the unit anchored with C(60) to the electrodes is masked by the modes arising from the anchoring groups. However, we have identified the additional modes from the fluorene backbone optically. 相似文献
42.
Peter Hammershøj Paul H. H. Bomans Dr. Rajamani Lakshminarayanan Jeppe Fock Stig Helmer Jensen Thomas Sand Jespersen Theis Brock‐Nannestad Tue Hassenkam Prof. Jesper Nygård Prof. Nico A. J. M. Sommerdijk Prof. Kristine Kilså Prof. Thomas Bjørnholm Dr. Jørn Bolstad Christensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(28):8716-8723
We describe herein the synthesis of a triptycene‐based surfactant designed with the ability to solubilise single‐walled carbon nanotubes (SWNTs) and C60 in water through non‐covalent interactions. Furthermore, an amphiphilic naphthalene‐based surfactant with the same ability to solubilise SWNTs and C60 has also been prepared. The compounds synthesised were designed with either two ionic or non‐ionic tails to ensure a large number of supramolecular interactions with the solvent, thereby promoting strong solubilisation. The surfactants produced stable suspensions in which the SWNTs are dispersed and the surfactant/SWNT complexes formed are stable for more than one year. UV/Vis/NIR absorption spectroscopy, TEM and AFM were employed to probe the solubilisation properties of the dispersion of surfactants and SWNTs in water. 相似文献
43.
Helena Gavilán Anja Kowalski David Heinke Abhilash Sugunan Jens Sommertune Miriam Varón Lara K. Bogart Oliver Posth Lunjie Zeng David González‐Alonso Christoph Balceris Jeppe Fock Erik Wetterskog Cathrine Frandsen Nicole Gehrke Cordula Grüttner Andrea Fornara Frank Ludwig Sabino Veintemillas‐Verdaguer Christer Johansson M. Puerto Morales 《Particle & Particle Systems Characterization》2017,34(7)
The assembly of magnetic cores into regular structures may notably influence the properties displayed by a magnetic colloid. Here, key synthesis parameters driving the self‐assembly process capable of organizing colloidal magnetic cores into highly regular and reproducible multi‐core nanoparticles are determined. In addition, a self‐consistent picture that explains the collective magnetic properties exhibited by these complex assemblies is achieved through structural, colloidal, and magnetic means. For this purpose, different strategies to obtain flower‐shaped iron oxide assemblies in the size range 25–100 nm are examined. The routes are based on the partial oxidation of Fe(OH)2, polyol‐mediated synthesis or the reduction of iron acetylacetonate. The nanoparticles are functionalized either with dextran, citric acid, or alternatively embedded in polystyrene and their long‐term stability is assessed. The core size is measured, calculated, and modeled using both structural and magnetic means, while the Debye model and multi‐core extended model are used to study interparticle interactions. This is the first step toward standardized protocols of synthesis and characterization of flower‐shaped nanoparticles. 相似文献
44.
ABSTRACTA string-based coupled-cluster method of general excitation rank, with optimal scaling and easy collection of all possible intermediates, which accounts for special relativity within the four-component framework is presented. The easy identification and collection of intermediates is achieved by extending the excitation-class formalism and introducing a contraction order for the operator indices. Initially, all possible contractions between the Hamiltonian and the intermediates with the cluster operator are found, stored and used for driving the algorithm, thereby defining an algorithm which allows for very complex state-selective, multi-reference, coupled-cluster calculations. The algorithm for solving the coupled-cluster equations can be used in both relativistic as well as non-relativistic calculations by appropriate restrictions in the excitation-class formalism. The capabilities of the new method are demonstrated in the application to the electronic ground state of the SbH molecule. In these calculations simulated multi-reference expansions with double, triple and quadruple excitations into the external space as well as the regular coupled-cluster hierarchy up to full quadruples excitations are compared. 相似文献
45.
Viktor Bliksted Roug Pedersen Jeppe Granhøj Andreas Erbs Hillers-Bendtsen Prof. Dr. Anders Kadziola Prof. Dr. Kurt V. Mikkelsen Prof. Dr. Mogens Brøndsted Nielsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(32):8315-8324
Polycyclic aromatic hydrocarbons (PAHs) have found strong interest for their electronic properties and as model systems for graphene. While PAHs have been studied intensively as single units, here PAHs were constructed in ladder-type arrangements using cross-conjugated fulvalene and dithiafulvalene motifs as connecting units and moving forward a convenient synthetic approach for dimerizing (thio)ketones into olefins by the action of Lawesson's reagent. Some of the PAHs can also be regarded as “super-extended” tetrathiafulvalenes (TTFs) with some of the largest cores ever explored, being multi-redox systems that exhibit both reversible oxidations and reductions. Concomitant absorption redshifts were observed when expanding the ladder-type structures from one to two to three indenofluorene units, and optical and electrochemical HOMO-LUMO gaps were found to correlate linearly. Various conformations (and solid-state packing arrangements) were studied by X-ray crystallography and computations. 相似文献
46.
47.
Olsen J Jørgensen P Helgaker T Oddershede J 《The journal of physical chemistry. A》2005,109(50):11618-11628
The linear and quadratic response functions have been derived for an exact state, based on an exponential parametrization of the time evolution consisting of products of exponentials for orbital rotations and for higher-order excitations. Truncating the linear response function such that the response function itself and its pole structure is correct to second order in M?ller-Plesset perturbation theory, we arrive at the second-order polarization propagator approximation (SOPPA). Previous derivations of SOPPA have used the superoperator formalism, making the extension of SOPPA to quadratic and higher order response functions difficult. The derivation of the quadratic response function is described in detail, allowing molecular properties such as hyperpolarizabilities, two-photon cross sections, and excited-state properties to be calculated using the SOPPA model. 相似文献
48.
Keld L. Bak Aage E. Hansen Kenneth Ruud Trygve Helgaker Jeppe Olsen Poul Jørgensen 《Theoretical chemistry accounts》1995,90(5-6):441-458
Summary The second-quantization magnetic dipole operator that arises when London atomic orbitals are used as basis functions is derived. In atomic units, the magnetic dipole operator is defined as the negative of the first derivative of the electronic Hamiltonian containing the interaction with the external magnetic field. It is shown that for finite basis sets, the gauge origin dependence of the resulting magnetic dipole operator is analogous to that of the exact operator, and that the derived operator converges to the exact operator in the limit of a complete basis set. It is also demonstrated that the length expression for the rotatory strength in linear response calculations gives gauge-origin-independent results. Sample calculations ontrans-cyclooctene and its fragments are presented. Compared to conventional orbitals, the basis set convergence of the rotatory strengths calculated in the length form using London atomic orbitals is favourable. The rotatory strength calculated fortrans-cyclooctene agrees nicely with the corresponding experimental circular dichroism spectrum, but the spectra for the fragment molecules show little resemblance with that oftrans-cyclooctene.Dedicated to Prof. Jan Linderberg 相似文献
49.
The conjugate residual with optimal trial vectors (CROP) algorithm is developed. In this algorithm, the optimal trial vectors of the iterations are used as basis vectors in the iterative subspace. For linear equations and nonlinear equations with a small-to-medium nonlinearity, the iterative subspace may be truncated to a three-dimensional subspace with no or little loss of convergence rate, and the norm of the residual decreases in each iteration. The efficiency of the algorithm is demonstrated by solving the equations of coupled-cluster theory with single and double excitations in the atomic orbital basis. By performing calculations on H(2)O with various bond lengths, the algorithm is tested for varying degrees of nonlinearity. In general, the CROP algorithm with a three-dimensional subspace exhibits fast and stable convergence and outperforms the standard direct inversion in iterative subspace method. 相似文献
50.
Jeppe Byskov-Nielsen Allan H. Holm Rune H?jsholt Pedro Sá Peter Balling 《Applied Physics A: Materials Science & Processing》2011,104(3):975-979
Micro-mechanical interlocking (MMI) can be applied to create new and interesting composite materials. We have employed laser
structuring to achieve MMI between stainless steel and plastic with extremely high joint strength. However, the water permeability
and corrosion resistance of the joint must be examined. For many industrially relevant applications it is important to keep
water away from certain parts and to prevent the sample from corroding. A thorough study of the permeability of the interconnected
samples at different temperatures and after employing different laser-structuring techniques is conducted. The permeability
seems to be consistent with the Hagen–Poiseuille equation independent of the laser structuring technique and is orders of
magnitudes larger than the diffusion rate through the plastic. Two different types of corrosion tests have been undertaken,
and we show that care must be taken in order not to degrade the corrosion resistance of the sample to an unacceptable level. 相似文献