293 research outputs found
Effets quantiques susceptibles d'intervenir dans les réactions unimoléculaires par Françoise Remacle. Rapports des Commissaires
No full textLiévin Jack, Reisse Jacques, Delmon Bernard. Effets quantiques susceptibles d'intervenir dans les réactions unimoléculaires par Françoise Remacle. Rapports des Commissaires. In: Bulletin de la Classe des sciences, tome 2, 1991. pp. 409-411
Tuning the Properties of Pd Nanoclusters by Ligand Coatings: Electronic Structure Computations on Phosphine, Thiol, and Mixed PhosphineThiol Ligand Shells
No full textpeer reviewedTuning the properties of Palladium nanoparticles using different protecting ligand shells is an important step toward the application-orientated design of nanoparticles for nano-electronics and catalysis. We present a density functional theoretical characterization of Pd13 and Pd55 metal cores protected by only-thiol, only-phosphine and mixed phosphine-thiol ligand shells. We analyze the ligand contributions to the frontier orbitals and the charge redistribution between the ligand shell and the metal core and show that these properties control the values of the charging energy and the catalytic activity. The charge transfer character of the metal-ligand interaction is influenced by the presence of other ligands in the capping system indicating a cooperative effect in the ligand induced charge redistribution. Because of the interplay between the stabilization of the frontier orbital due to the contribution of the sulfur and the charge donation by the phosphine, the charging energy of the mixed phosphine-thiol protected cluster is larger than that of the only-phosphine and the only-thiol systems. The complementary point of view is adopted for rationalizing the catalytic properties of the clusters by analyzing the effect of the interaction with the metallic core on the properties of the ligand. The impact of solvation on the electronic structure of the ligand capped Pd13 cluster is investigated by including explicitly a layer of water molecules in the model system
Atomistic account of structural and dynamical changes induced by small binders in the double helix of a short DNA
No full textpeer reviewe
An atomistic view of DNA dynamics and its interaction with small binders: insights from Molecular Dynamics and Principal Component Analysis
No full textpeer reviewedDNA oligomers are promising building blocks for the development of bottom-up nano-devices and molecular logic machines. To control and exploit their unique capabilities of self-assembling and molecular recognition a deep understanding of their dynamical properties is essential. We theoretically investigate the dynamics of a DNA dodecamer and its complexes with two common ligands, Hoechst33258 and the ethidium cation, by means of classical Molecular Dynamics (MD) simulations and Principal Component Analysis (PCA). We study the structural relation between the flexibility of the double helix and the binding process. The dynamics of a terminal base pair unbinding is also analysed as an example of process that involves multiple energy minima in the underlying free energy landscape
Implementation of probabilistic algorithms by multi-chromophoric molecular networks with application to multiple travelling pathways
No full textpeer reviewe
Ultrafast dynamics of LiH molecule induced by ultrashort optical pulses. Influence of photoionization on the electronic coherence
No full textUpon excitation by strong IR and UV few femtosecond pulses, LiH molecules can undergo both electronic excitation and photoionization. The simultaneous excitation into several electronic excited states leads to a coherent superposition of electronic states in the neutral and in the cation1 (Fig. 1). The evolution of the coherence after the end of the pulse is determined both by the energy difference between the states involved in the superposition and by the phase relation between each component of the superposition2. The phase and the amplitude of each component is itself built by the complex transient dynamics taking place during the initial excitation that involves interaction with the photoionization continuum. It is also influenced by the non- adiabatic coupling induced by nuclear motion3. To suitably represent the evolution of the coherence induced upon excitation by such pulses, methodologies that include both electronic excitation, nuclear motion and photoionization are needed to compute the dynamics.
We will report on the computation of coupled electronic-nuclear dynamics in the LiH molecule on several excited electronic states and including multiphoton ionization. We compute the dynamics by numerically integrating the nuclear time-dependent Schrödinger equation on a spatial grid and on several potential energy surfaces. We include the photoionization process using the partitioning method4. The wave function of the ionized states is represented as an antisymmetrized product of the electronic states of the cation and of the states of the photoelectron. A set of orthogonalized plane waves is used for the photoelectron. The coupling between the wave function of the neutral and the wave function of the cation is computed at each grid point in nuclear coordinates as the transition dipole between the photoelectron wave function and the Dyson orbital that is defined as the overlap between the electronic state of the neutral and the electronic state of the cation. This method allows us computing the dynamics of LiH upon excitation by strong IR and UV femtosecond pulses. Depending on the pulse parameters, the dissociation of the LiH molecule yields a lithium atom in different electronic states.
[1] B. Mignolet, R. D. Levine, and F. Remacle, Phys. Rev. A 89, 021403(R)
[2] S. van den Wildenberg, B. Mignolet, R. D. Levine, F. Remacle, Phys. Chem. Chem. Phys., 2017,19, 19837-19846
[3] Astrid Nikodem, R. D. Levine, and F. Remacle, Phys. Rev. A 95, 053404
[4] R. D. Levine, Quantum Mechanics of Molecular Rate Processes (Oxford University Press, 1969)
Steering chemical reactions with mechanical forces and attosecond optical pulses
No full textExternal mechanical forces and ultrashort optical pulses can be used to steer and control chemical
reactions. We demonstrate that an external mechanical force can not only enhance or inhibit the
[4+2] cycloreversion of furan/maleimide Diels-Alder adducts, but also shift its mechanism from
concerted to stepwise, mediated by diradical species. To better understand how attosecond light
pulses can control photochemical reactions, we derived an expression for the force exerted on the
nuclei by the electronic coherences created through interaction with the light and show that they
can be used to steer nuclear motion. We propose a computational scheme based on singular value
decomposition to simplify the simulation of an ensemble of molecules with random initial
orientations interacting with an attopulse. We show that a few principal orientations only suffice
to describe the ensemble dynamics and that electronic coherences are robust with respect to the
ensemble averaging. We also show that conical intersections control the relaxation of the excited
ethylene cation, shaping the yields of fragments after dissociation. Our findings contribute to a
better understanding of control mechanisms in the fields of mechanochemistry and attochemistry
Ultrafast coupled electronic-nuclear dynamics of small molecules induced by few femtosecond optical pulses
No full textMechanistic, redox and photochemistry quantum and classical/quantum studies of organic and bio-molecular complexes
No full textMagnetostructural effects in ligand stabilized Pd13 clusters: a density functional theory study
No full textpeer reviewe
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