Diagramme d'orbitales moléculaires

Un diagramme des niveaux d’énergie des orbitales moléculaires, ou diagramme d'orbitales moléculaires, est un outil qualitatif fondé sur la théorie des orbitales moléculaires et en particulier sur la méthode de combinaison linéaire des orbitales atomiques. D'après ces théories, lorsque des atomes se lient pour former une molécule, un certain nombre d'orbitales atomiques se combinent pour former le même nombre d'orbitales moléculaires. Un diagramme d'orbitales moléculaires représente les niveaux d'énergie de ces orbitales moléculaires. Cet outil est particulièrement approprié à la description des molécules diatomiques. Il peut permettre par exemple d'expliquer pourquoi des molécules existent dans la nature et d'autres non, la force relative de liaisons chimiques ainsi que l'origine de certaines propriétés physiques comme le moment dipolaire et le diamagnétisme ou le paramagnétisme de molécules. Dans cet article, OM est utilisé pour Orbitale Moléculaire et OA pour Orbitale Atomique.

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Liaison covalente

Une liaison covalente est une liaison chimique dans laquelle deux atomes se partagent deux électrons (un électron chacun ou deux électrons venant du même atome) d'une de leurs couches externes afin de

Ordre de liaison

L'ordre de liaison (ou indice de liaison) est le nombre de liaisons chimiques entre une paire d'atomes. Par exemple, dans le diazote N≡N, l'ordre de liaison entre les atomes d'azote est 3, de même p

Orbitale moléculaire

vignette|Orbitales moléculaires du 1,3-butadiène, montrant les deux orbitales occupées à l'état fondamental : π est liante entre tous les atomes, tandis que π n'est liante qu'entre les atomes C et C a

CH-223: Organometallic chemistry

Basic organometallic chemistry will be covered in this course.

Structure and bonding in organometallic compounds.
reactivity of organometallic compounds, stoichiometric reactions, catalyzed reactions and reaction mechanisms.

MSE-486: Organic electronic materials

This course will introduce students to the field of organic electronic materials. The goal of this course is to discuss the origin of electronic properties in organic materials, charge transport mechanisms, chemical synthesis, materials processing, and device fabrication.

MSE-304: Surfaces and interfaces

This lecture introduces the basic concepts used to describe the atomic or molecular structure of surfaces and interfaces and the underlying thermodynamic concepts. The influence of interfaces on the properties of materials is also discussed.

The influence of external electric fields on charge reorganization energy in organic semiconductors

Weicong Huang, Hongguang Liu

Charge reorganization energies (k) of inter-ring carbon-carbon (IRCC) bond connected conjugated polycyclics are shown to exhibit an electric-field-driven anisotropic character. An external electric field parallel to the IRCC linker(s) reduces k while the field vertical to the molecular plane does the opposite. This anisotropic character can be modulated by introducing inter-ring noncovalent locks into appropriate sites.

ROYAL SOC CHEMISTRY2019

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Interaction of carbon dioxide with Ni(110): A combined experimental and theoretical study

We present a combined experimental and theoretical study of the CO2 interaction with the Ni(110) surface. Photoelectron spectroscopy, temperature-programmed desorption, and high-resolution electron energy loss spectroscopy measurements are performed at different coverages and for increasing surface temperature after adsorption at 90 K with the aim to study the competing processes of CO2 dissociation and desorption. Simulations are performed within the framework of density functional theory using ab initio pseudopotentials, focusing on selected chemisorption geometries, determining the energetics and the structural and vibrational properties. Both experimental and theoretical vibrational frequencies yield consistent indications about two inequivalent adsorption sites that can be simultaneously populated at low temperature: short-bridge site with the molecular plane perpendicular to the surface and hollow site with the molecular plane inclined with respect to the surface. In both sites, the molecule has pure carbon or mixed oxygen-carbon coordination with the metal and is negatively charged and bent. Predicted energy barriers for adsorption and diffusion on the surface suggest a preferential adsorption path through the short-bridge site to the hollow site, which is compatible with the experimental findings. Theoretical results qualitatively support literature data concerning the increase of the work function upon chemisorption.

2007

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Emergent nonlinear phenomena in a driven dissipative photonic dimer

Mikhail Churaev, Hairun Guo, Tobias Kippenberg, Junqiu Liu, Alexey Tikan, Rui Ning Wang

Collective effects leading to spatial, temporal or spatiotemporal pattern formation in complex nonlinear systems driven out of equilibrium cannot be described at the single-particle level and are therefore often called emergent phenomena. They are characterized by length scales exceeding the characteristic interaction length and by spontaneous symmetry breaking. Recent advances in integrated photonics have indicated that the study of emergent phenomena is possible in complex coupled nonlinear optical systems. Here we demonstrate that the out-of-equilibrium driving of a strongly coupled pair of photonic integrated Kerr microresonators ('dimer')-which, at the 'single particle' (that is, individual resonator) level, generate well-understood dissipative Kerr solitons-exhibits emergent nonlinear phenomena. By exploring the dimer phase diagram, we find regimes of soliton hopping, spontaneous symmetry breaking and periodically emerging (in)commensurate dispersive waves. These phenomena are not included in the single-particle description and are related to the parametric frequency conversion between the hybridized supermodes. Moreover, by electrically controlling the supermode hybridization, we achieve wide tunability of spectral interference patterns between the dimer solitons and dispersive waves. Our findings represent a step towards the study of emergent nonlinear phenomena in soliton networks and multimodal lattices. A pair of strongly coupled photonic microresonators shows nonlinear emergent behaviour, which can be understood by incorporating interactions in the theoretical description of nonlinear optical systems.

NATURE RESEARCH2021

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