Search results for " molecule"
showing 10 items of 1523 documents
Time-dependent density-functional theory in the projector augmented-wave method
2008
We present the implementation of the time-dependent density-functional theory both in linear-response and in time-propagation formalisms using the projector augmented-wave method in real-space grids. The two technically very different methods are compared in the linear-response regime where we found perfect agreement in the calculated photoabsorption spectra. We discuss the strengths and weaknesses of the two methods as well as their convergence properties. We demonstrate different applications of the methods by calculating excitation energies and excited state Born–Oppenheimer potential surfaces for a set of atoms and molecules with the linear-response method and by calculating nonlinear e…
Two atropisomers of tricarbonyl[η6-7-chloro-3-(3-chloro-2-methylphenyl)-2,4,8-trimethyl-1,2,3,4-tetrahydro-2,4-dibora-1,3-diazanaphthalene]chromium(0)
2001
The structures of two atropisomers of the title compound, [Cr(C16H18B2Cl2N2)(CO)3], are reported. For both compounds, the Cr(CO)3 moiety is bound to the C6 aromatic ring of the molecule; the existence of atropisomers resulting from the non-equivalence of both faces of the C6 aromatic ring is a consequence of the 3-chloro-2-methylphenyl ring being nearly perpendicular to the mean plane of the 2,4-dibora-1,3-diazanaphthalene ring. The orientation of the Cr(CO)3 tripod relative to the C6 aromatic ring is such that it is nearly eclipsed in one isomer (2.4° rotation from being eclipsed with C—N, C—Cl and C—H) and slightly twisted (16.2°) from an eclipsed conformation in the other.
Dynamique induite par champ laser femtoseconde intense : alignement moléculaire en milieu gazeux dense et effet Kerr
2011
This thesis is devoted to the study of dynamics induced by intense femtoseconds lasers pulses. The first studied dynamics deals with molecular alignment of CO2-X mixtures (X=CO2, Ar, N2), in dense gases (up to 20 bar). Up to now, this regime has never been studied experimentally. In the field-free regime (after laser/matter interaction), molecular alignment exhibits two components : a permanent alignment and a transient one. The influence of collisions appears through population transfers between rotational states, which leads to a decrease of these two contributions. Permanent alignment relaxation time is only tied to inelastics collisions whereas transient alignment relaxation time is tie…
Thermal 1,6-Electrocyclization Reactions of Acceptor-Substituted 2,3-Divinyl-1H-indoles Yielding Functionalized Carbazoles
1990
Three new synthetic procedures for and thermal 1,6-electrocyclizations of acceptor-substituted 2,3-divinyl-1H-indoles leading to functionalizing carbazoles are described. The scope and limitations as well as some mechanistic aspects of the methodologies are discussed. The key strategies employed include Pd(II)-catalyzed coupling and Wittig procedures.
Rescattering and vibrations in homonuclear diatomic molecules in a strong electromagnetic field
2009
Abstract The electron of a H 2 + driven by a strong electromagnetic field induces molecular vibrations. Numerical and analytical results show that the molecule behaves as a parametric oscillator and can be treated as a kicked oscillator. The results are discussed from the point of view of the electron's periodic dressing and undressing processes.
Spectral Analysis of Nonrelativistic Quantum Electrodynamics
2001
I review the research results on spectral properties of atoms and molecules coupled to the quantized electromagnetic field or on simplified models of such systems obtained during the past decade. My main focus is on the results I have obtained in collaboration with Jurg Frohlich and Israel Michael Sigal [8, 9, 10, 11, 12, 13].
Inter- and intramolecular bonding in 1,3,5-triamino-2,4,6-trinitrobenzene: An experimental and theoretical quantum theory of atoms in molecules (QTAI…
2017
Chemical bonding in the triclinic phase of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) has been analyzed based on the experimental electron density derived from X-ray diffraction data obtained at 20 K. The results have been compared with those from solid state theoretical calculations. The total electron density has been analyzed in terms of the Quantum Theory of Atoms in Molecules (QTAIM). Features of the covalent bonds demonstrate the presence of multiple bonds of various order. Strong intramolecular hydrogen bonds and weaker intermolecular bonds within the layer structure are characterized by the properties of their (3, −1) critical points. Weaker interactions, predominantly O···O, betwe…
Partial Reduction and Selective Transfer of Hydrogen Chloride on Catalytic Gold Nanoparticles
2017
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim HCl in solution accepts electron density from Au NPs and partially reduces at room temperature, as occurs with other simple diatomic molecules, such as O2 and H2. The activation can be run catalytically in the presence of alkynes to give exclusively E-vinyl chlorides, after the regio- and stereoselective transfer of HCl. Based also on this method, vinyl chloride monomer (VCM) can be produced in a milder and greener way than current industrial processes.
Aromaticity in Pericyclic Transition State Structures? A Critical Rationalisation Based on the Topological Analysis of Electron Density
2016
The nature of the electron delocalisation pattern within a cyclic structure, i. e. the aromatic character, is examined for six-membered pseudocyclic transition state structures (TSs) involved in five representative examples of so-called pericyclic reactions. Results of the electron localisation function (ELF) and the quantum theory of atoms in molecules (QTAIM) analyses of the electron density evidence that in four of the cases, at least one pair of atoms are not bound at the TS configuration, thus precluding a possible cyclic conjugation. These findings make it possible to rule out the aromatic character of these TSs. High values of the synchronicity Sy index at the TSs contrast with the b…