http://hdl.handle.net/10256.1/1672 Electron Density, Density Matrices, and Density Functional Theory Thu, 12 Feb 2026 13:18:40 GMT 2026-02-12T13:18:40Z http://hdl.handle.net/10256.1/1738 Closing Solà i Puig, Miquel Closing of IX Girona Seminar: Electron Density, Density Matrices, and Density Functional Theory, dedicated to Prof. Ramon Carbó-Dorca on occasion of his 70th birthday Thu, 08 Jul 2010 00:00:00 GMT http://hdl.handle.net/10256.1/1738 2010-07-08T00:00:00Z http://hdl.handle.net/10256.1/1737 Aromaticity and the electron localization function, ELF Fuentealba, Patricio It will be shown that the Electron Localization Function, ELF, can also be used to study the delocalization and aromatic character of a diversity of molecules. Although the analysis of the total ELF does not provide clear information about aromaticity, the separation of the function on its σ and π parts yields indeed valuable information about it. Moreover, it is possible to construct a quantitative scale of aromaticity. It is also shown that the use of the ELF to understand aromaticity is complementary to other methodologies. Applications to organic and inorganic molecules and atomic clusters demonstrate the capability of the method and the possibility of distinguish between σ , π , δ… aromaticity Thu, 08 Jul 2010 00:00:00 GMT http://hdl.handle.net/10256.1/1737 2010-07-08T00:00:00Z http://hdl.handle.net/10256.1/1736 Spin-coupled descriptions of organic reactivity Cooper, David Valence bond theory has undergone something of a resurgence in chemistry over the last few decades, with a key role being played by so-called modern valence bond approaches such as spin-coupled theory. Given that spin-coupled theory uses the most general wavefunction based on a single orbital product, it arguably represents the highest level of theory at which one can obtain such models directly, thereby combining useful accuracy with highly visual descriptions of correlated electronic structure. We survey recent applications of spin-coupled theory to the electronic rearrangements associated with the bondbreaking and bond-formation processes along the minimum energy paths in organic chemical reactions Thu, 08 Jul 2010 00:00:00 GMT http://hdl.handle.net/10256.1/1736 2010-07-08T00:00:00Z http://hdl.handle.net/10256.1/1735 Spin component scaling in multiconfiguration perturbation theory Szabados, Agnes We investigate a term-by-term scaling of the second order energy correction obtained by perturbation theory (PT) based on a multiconfiguration wavefunction. The total second order correction is decomposed into several terms, based on the level and spin pattern of the excitations. In particular, same spin and different spin double excitations are grouped separately in the spirit of spin component scaling (SeS). Identification of the excitation level is facilitated by the pivot determinant underlying the multiconfiguration PT framework. Scaling factors of the individual terms are determined from the stationary condition of the total energy calculated up to order three. In the single reference framework this procedure has been shown to result scaling factors similar to those applied in Grimme's SeS-M011er-Plesset method. Several decomposition schemes are tested numerically on the example of bond dissociation profiles. We conclude, that the success of spin component scaling at around equilibrium geometries is not right away transferable to the entire potential surface, even if adopting a multireference based PT formulation Thu, 08 Jul 2010 00:00:00 GMT http://hdl.handle.net/10256.1/1735 2010-07-08T00:00:00Z