Différences entre les versions de « ELF abstracts page »
| Ligne 331 : | Ligne 331 : | ||
<big> '''The Electron Localization Function at the Correlated Level: A Natural Orbital Formulation.''' </big> | <big> '''The Electron Localization Function at the Correlated Level: A Natural Orbital Formulation.''' </big> | ||
| − | The | + | The ELF is nowadays used in a wide context, including aromaticity, chemical bonding or reaction mechanisms. |
| − | + | Some of these analyses involve the calculation of the second-order density matrix (DM2).<sup>1</sup> The DM2 | |
| − | the calculation of the ELF | + | is present in both the calculation of the ELF and the population analysis (variance, covariance) of the ELF |
| − | In particular, we use approximate expressions | + | basins. |
| + | However, it is possible to lower the numerical complexity of the calculation of the localization function as | ||
| + | well as that of the pair populations using approximated expressions for the calculation of DM2. | ||
| + | In particular, we use approximate expressions based on the formula for the monodeterminantal wavefunctions | ||
(X-HF in the graph below) and the formula of Müller in terms of natural orbitals.<sup>3</sup> | (X-HF in the graph below) and the formula of Müller in terms of natural orbitals.<sup>3</sup> | ||
The approximation has been tested in a set of molecules, | The approximation has been tested in a set of molecules, | ||
NH<sub>3</sub>, CO<sub>2</sub>, H<sub>2</sub>O, CO, CN<sup>-</sup>, NO<sup>+</sup>, N<sub>2</sub>, | NH<sub>3</sub>, CO<sub>2</sub>, H<sub>2</sub>O, CO, CN<sup>-</sup>, NO<sup>+</sup>, N<sub>2</sub>, | ||
H<sub>2</sub>O<sub>2</sub>, F<sub>2</sub> and FCl<sup>-</sup>, which have been calculated using a plethora of | H<sub>2</sub>O<sub>2</sub>, F<sub>2</sub> and FCl<sup>-</sup>, which have been calculated using a plethora of | ||
| − | methods: HF, B3LYP, MP2, CISD, CCSD and CASSCF. | + | methods: HF, B3LYP, MP2, CISD, CCSD and CASSCF. |
| − | + | The present approach aims at a correlated version of the ELF which can be used in medium size molecules. | |
[[File:profile_CO.jpg|700px|Profile for CO molecule along the molecular axis. Left (R=1.23A). Right (R=2.0A)|center]] | [[File:profile_CO.jpg|700px|Profile for CO molecule along the molecular axis. Left (R=1.23A). Right (R=2.0A)|center]] | ||
Version du 20 mai 2010 à 19:59
SPEAKERS : please add below, in your own section, your title talk and abstract :
- first : log in;
- click on your name in the "Contents" box below, this will lead you to your own section;
- your section starts with your name as the title line, click on [edit] (far right).
The order of abstract follow the program of the workshop.
E. Alikhani
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P. Hiberty
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C. Lepetit
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M-M. Rohmer
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B. De Courcy
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H. Jamet
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G. A. Cisneros
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X. Assfeld
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H. S. Rzepa
Department of Chemistry, Imperial College London
ELF and the Nature of Triple bonds
A recent report of the species HOS≡CH by Schreiner, Mloston and co-workers1 speculated upon the nature of the SC bond; did it have triple significant bond character? Of the various techniques these authors used for the analysis, neither QTAIM nor ELF was employed. I initially filled this gap by a post on my blog2, and followed this by a full article submitted for publication more conventionally3. The results of this investigation will be presented at the workshop, including a rather surprising conclusion regarding the nature of triple bonds themselves in relation to the degree of charge-shift character they display4. The hypothesis so generated was then extended to investigating the nature of metal-metal multiple bonds, particularly Cr-Cr whose compounds are purported to exhibit homonuclear quadruple or quintuple bonds5. These systems also appear to sustain remarkably high charge-shift character and most intriguing ELF behaviour. The issue for discussion in the workshop is therefore whether or not ELF (combined with QTAIM) is indeed revealing something new about the nature of the triple and higher order homonuclear (metal) bond.
The talk will appear @www.ch.ic.ac.uk/rzepa/talks/elf10 and will feature rotatable ELF isosurfaces and models.
References
[1] P. R. Schreiner, H. P. Reisenauer, J. Romanski, and G. Mloston, Angew. Chemie. 2009, 48, 8133-8136. DOI: 10.1002/anie.200903969
[2] H. S. Rzepa, Blog and follow up
[3] H. S. Rzepa, submitted for publication, 2010.
[4] S. Shaik, D. Danovich, W. Wu and P. C. Hiberty, Nature Chem., 2009, 1, 443-449. DOI: 10.1038/nchem.327
[5] For initial speculations, see blog.
M. Yanez
Departamento de Química, C-9. Universidad Autónoma de Madrid. Cantoblanco, 28049-Madrid. Spain
ELF as a useful tool to understand chemical bonding in challenging cases
Quite unexpectedly, substituent effects on the structure of iminoboranes are opposite to those observed for the acetylene derivatives in spite of the fact that both series of compounds are isoelectronic. [1] More importantly these dissimilarities cannot be easily explained in terms of the atoms in molecules (AIM) theory or in terms of the population of the πBN* or πCC* antibonding orbitals. In some molecules a decrease (increase) of the electron density is unexpectedly reflected in a shortening (lengthening) of the bond. Conversely, the ELF analysis offers a clear picture of the substituent effects on the CC and BN bonding. The dissimilarities between acetylene- and iminoborane derivatives are primarily a consequence of the strong electronegativity difference between the B and N atoms in the iminoboranes. This difference is the origin of the significant distortion of the BN bonding electron density in iminoboranes, which is not seen in the corresponding acetylene analogues.
References
[1] O. Mó; M. Yáñez; A. Martín Pendás; J.E. Del Bene; I. Alkorta and J. Elguero, Phys. Chem. Chem. Phys. 9, 3970 (2007)
P. J. MacDougall
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J. Angyan
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M. Causa
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J. Contreras-Garcia
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D. L. Cooper
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A. Lüchow
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E. P. Fowe
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S. Grabowski
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A. M. Pendas
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E. Matito
Institute of Physics, University of Szczecin, Poland
The Electron Localization Function at the Correlated Level: A Natural Orbital Formulation.
The ELF is nowadays used in a wide context, including aromaticity, chemical bonding or reaction mechanisms. Some of these analyses involve the calculation of the second-order density matrix (DM2).1 The DM2 is present in both the calculation of the ELF and the population analysis (variance, covariance) of the ELF basins. However, it is possible to lower the numerical complexity of the calculation of the localization function as well as that of the pair populations using approximated expressions for the calculation of DM2. In particular, we use approximate expressions based on the formula for the monodeterminantal wavefunctions (X-HF in the graph below) and the formula of Müller in terms of natural orbitals.3 The approximation has been tested in a set of molecules, NH3, CO2, H2O, CO, CN-, NO+, N2, H2O2, F2 and FCl-, which have been calculated using a plethora of methods: HF, B3LYP, MP2, CISD, CCSD and CASSCF. The present approach aims at a correlated version of the ELF which can be used in medium size molecules.
References
[1] Matito E., Silvi B., Duran M. and Solà M., J. Chem. Phys. 125, 024301 (2006)
[2] Feixas F., Matito E., Duran M., Solà M. and Silvi B., in preparation.
[3] Müller A.M.K., Phys. Lett. 105A, 446 (1984)
D. Borgis
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R. Vuillemier
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J. Cioslowski
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J. Pilmé
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R. Nesper
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Y. Grin
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J-F. Halet
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U. Wedig
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R. Weihrich
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P. Raybaud
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E. Dumont
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N. Chéron
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S. Berski
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L. Joubert
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H. Bolvin
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A. Delalande
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R. Nalewajski
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A. Scemama
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J. Tao
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I. Fourré
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H. Gérard
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N. Russo
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