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Développement et application de méthodes corrélées pour la description de systèmes moléculaires

Abstract : In the last few years, a lot of energy has been put forward in the area of quantum chemistry to develop new methods, or to improve existing methods, that are able to describe very precisely the electronic structure of molecular systems. In this manuscript, a precise overview of such a method (namely the Density Matrix Renormalization Group, DMRG method) is given. A software able to carry out DMRG calculations has indeed been developed from scratch in the laboratory during this thesis. This method can be seen as a post-Hartree-Fock method, in which only the electronic states that are relevant for the correct description of the molecule are kept. In this way, the computational cost remains acceptable, and the results are in line with those given by "exact" methods such as full-CI. Density Functional Theory (DFT) has also been investigated in this work. DFT and TD-DFT calculations have indeed also been carried out. The performances of two middle-range-separated functionals, namely HISS-A and HISS-B, to describe electronic transitions in conjugated molecules have been probed in a theory vs. theory study. Those functionals, which had been first developed for the study of metals, show to be adequate for the correct description of electronic excitations of chromophores and of push-pull molecules. Optical properties of a dual emittor have also been studied using TD-DFT. The dual emission of this molecule has been shown to stem from the presence of two distinct emissive states, respectively of Intramolecular Charge Transfer (ICT) and locally excited (LE) nature. TD-DFT has allowed us to link those two emissive states to two different conformations of the molecule.
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Submitted on : Tuesday, November 18, 2014 - 12:37:07 PM
Last modification on : Friday, January 8, 2021 - 12:16:02 PM
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  • HAL Id : tel-01084000, version 1


Romain Paulino Neto. Développement et application de méthodes corrélées pour la description de systèmes moléculaires. Chimie théorique et/ou physique. Université Pierre et Marie Curie - Paris VI, 2014. Français. ⟨NNT : 2014PA066216⟩. ⟨tel-01084000⟩



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