Configuration électronique | EPFL Graph Search

redresse=1.6|vignette|Planche synthétisant la règle de Klechkowski (en haut à gauche) de remplissage des sous-couches électroniques ; en haut la géométrie des quatre types d'orbitales atomiques ; au centre la géométrie de quelques orbitales moléculaires ; en bas le nombre maximum d'électrons pouvant occuper les atomiques connues à l'état fondamental. En physique des particules comme en chimie quantique, la configuration électronique, également appelée structure électronique ou formule électronique, décrit la distribution des électrons d'un atome, d'une molécule ou d'une espèce chimique dans un ensemble de fonctions d'onde correspondant à des orbitales atomiques ou à des orbitales moléculaires. Par exemple, la configuration électronique à l'état fondamental d'un atome d'oxygène est , tandis que celle d'une molécule de dioxygène est , d'où, en spectroscopie, les multiplets , et . Une configuration électronique est entièrement déterminée par la connaissance des spinorbitales de chaqu

Seismic vulnerability assessment at large scale city of Basel

Romain Savoy

The Basel region is one of the most seismically active regions in Switzerland. Already devastated by Nature in 1356, the city of Basel is now actively involved in assessing the seismic risk on its buildings in order to protect its patrimony and its population as effectively as possible. Through innovative assessment methods, researchers and scientists throughout Switzerland are working to effectively and accurately assess seismic risk through the three components that define it: hazard, exposure and vulnerability. It is this latter element that is addressed in this report. While the assessments carried out so far deal with the buildings one by one, an essential aspect of Basel's built environment is hidden in the row configurations of many buildings. Indeed, due to the desire to optimize space, many buildings are adjacent to each other, modifying thus their seismic behaviour. This document is therefore a first study of the vulnerability of building rows in order to reveal whether the effects of this particular configuration are beneficial or not. Thanks to epoch plans collected from the archives of the Canton of Basel-Stadt and dynamic simulations based on the Applied Element Method, the consequences on the vulnerability of two types of rows of masonry buildings are estimated. As a conclusion, the impact of introducing new fragility curves on the assessment of damage in the Iselin district makes it possible to highlight the effects of taking into account the row configuration of the buildings it contains.

2020

Characterization and prediction of peptide structures on inorganic surfaces

Dmitrii Maksimov

Interfaces between peptides and metallic surfaces are the subject of great interest for possible use in technological and medicinal applications, mainly since organic systems present an extensive range of functionalities, are abundant, cheap, and exhibit low toxicity. Exemplary applications are biosensors that may be sensitive to specific metabolites or harmful compounds. However, these hybrid interfaces pose a challenge to computational modelling, particularly regarding predicting the most relevant configurations at the surface, which determines the electronic properties of the system as a whole. From a theoretical point of view, predicting the most stable interface configuration requires searching through the enormous structure space of flexible biomolecules with respect to the surface for different configurations and performing computational calculations of their properties. However, it is impossible to investigate those parts separately due to complex interactions during adsorption. In order to capture these complex interactions, one has to employ accurate theoretical methods, which are very computationally expensive. In this thesis, we provide a comprehensive description of the complex nature of the interaction of selected amino acids with metallic surfaces using state-of-the-art dimensionality reduction techniques and accurate ab initio theoretical methods and creation of tools tailored for the high-throughput investigations of interface systems. The theoretical methods used in the thesis are described in the first part of the thesis. The second section looks into the conformational space changes of Arginine (Arg) and its protonated counterpart after adsorption on three noble metallic surfaces. Arg is an excellent testbed because it is tiny enough to be treated using density functional theory, which is considered the best compromise between accuracy and computational efficiency. At the same time, Arg is complex enough due to a highly flexible side-chain that allows for hundreds of different configurations in the gas phase alone. The examination of adsorption behavior requires creating a database by performing a large number of geometry optimizations of various conformations and orientations. The investigation of that database includes creating a low-dimensional representation of the conformational spaces using recent dimensionality reduction techniques, followed by examining various bonding and charge transfer patterns and how they affect the available conformational spaces.The third section of the thesis is concerned with developing tools for the automated structure search of interface systems and the modelling of self-assembly patterns formed after adsorption. Different geometry optimization algorithms and a flexible method of preconditioning the quasi-Newton optimization algorithms are implemented in the GenSec package that was developed. Together, these enable a more straightforward interface with a wide range of quantum chemistry packages for sampling the conformational spaces of flexible molecules in 1D (ions), 2D (surfaces), and 3D (cavities and molecules) systems. Structure search of the conformational space of a flexible molecule using GenSec provided satisfactory results for di-L-alanine adsorbed on Cu(110) surface.

EPFL2022

Phase Gradient Estimation Techniques in Fringe Analysis

Rajshekhar Gannavarpu

The thesis introduces novel techniques in the field of fringe analysis for direct estimation of phase gradients or derivatives. A pseudo Wigner-Ville distribution based method is proposed to reliably estimate the phase derivatives from a single fringe pattern. The method's ability for estimating rapidly varying phase derivatives is enhanced by developing an adaptive windowing technique. Further, the two-dimensional extension of the method is presented to handle fringe patterns with severe noise. In addition, a generalized approach is described to enable direct estimation of arbitrary order phase derivatives. Subsequently, methods based on digital holographic moiré and multi-component polynomial phase formulation are introduced to measure the in-plane and out-of-plane displacements and their derivatives for a deformed object in digital holographic interferometry. These methods permit the simultaneous estimation of multiple phases and their derivatives without the need of multiple fringe patterns and complex experimental configurations, which is hitherto not possible with the current state-of-the-art fringe analysis methods. The major advantages of the developed techniques are the ability to directly estimate phase derivatives without relying on complex unwrapping, filtering and numerical differentiation operations, high computational efficiency and strong robustness against noise. In addition, the requirement of a single fringe pattern makes these techniques less error-prone in the presence of vibrations and external disturbances and enhances their applicability for dynamic measurements. Further, the developed techniques offer a potential solution to the challenging problem of simultaneous multi-dimensional deformation analysis in digital holographic interferometry. The reliable performance of these techniques is validated by numerical simulation and their practical applicability is demonstrated in digital holographic interferometry and fringe projection for slope and curvature measurement, defect detection, surface slope evolution studies and measurement of in-plane and out-of-plane displacements and their derivatives. These techniques offer substantial advancements in fringe analysis and exhibit significant application potential in areas such as non-destructive testing, biomechanics, reliability analysis, material characterization and experimental mechanics.

EPFL2012