Biomedical subjects

Fabienne Alary

Publications and source records attributed to Fabienne Alary.

3 recordsLinked to original sources

PubMed2004

A study of the correlation effects upon the modelization of the double exchange phenomenon.

A previous work by the authors has shown that the usual spin Hamiltonian used to model the magnetic spectra of mixed valence compounds was not sufficient to reproduce the magnetic spectrum of the molecule [Fe(2)(OH)(3)(NH(3))(6)](2+). In the present paper, the spin Hamiltonian is confronted to correlated ab initio calculations. The discrepancy between this Hamiltonian and the calculations is investigated and explained. It is pointed out that the multiconfigurational nature of the transition metal is responsible for this discrepancy. However, we show that this effect can easily be treated at the complete active space self-consistent field (CASSCF) level and that no further correlation treatment is needed. The spin Hamiltonian, which reproduces very well the minimal CASSCF results, could not be improved to recover the multireference effects.

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PubMed2004

Calculation of the ground and excited states of a mixed valence compound [Fe2(OH)3(NH3)6]2+: a class II or class III compound?

The effective group potentials (EGP) approach has been successfully used for the computation of the ground and excited states energies of the mixed valence compound [Fe2(OH)3(NH3)6]2+. It is the first time that for a system as big as the complex presented above the ground and excited states are computed with their own orbitals and studied in such a detailed way. First of all, the NH3 EGP was validated by comparing calculations where NH3 was treated explicitly at different levels of calculations. Once the validation was obtained, the complete spectrum of the compound under interest was calculated and compared with results obtained in a previous work by Barone et al. and the spin Hamiltonian of widespread use. Some deviations from these predictive approaches were observed. This allowed us to emphasize the importance of the dynamic correlation which is not included explicitly in the spin Hamiltonian. Then, the influence of vibration has been studied by computing the potential energy curves obtained when moving the (OH)3 plane. This study shows that our calculations lead to a delocalized compound (class III) as expected according to former experimental data.

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PubMed2003

Using effective group potential methodology for predicting organometallic complex properties.

Using the Effective Group Potentials (EGP) method, optimal geometries, harmonic vibrational frequencies, and relative energies of different sets of metal complexes are calculated. All of the systems under consideration contain the cyclopentadienyl (Cp) ligand. They are as follows: (i). Group V metal Atom complexes showing one Cp ligand, (ii). a tetrameric Al-Cp compound with four Cp ligands, (iii). homometallic lutetium hydrides containing six cyclopentadienyl rings. Various electron correlation treatments have been carried out. All of the results compare very satisfactorily with available experimental data and with all-electron ab initio calculations performed for this work or published in the literature. Furthermore, the performance of the EGP method was tested on a rather large complex for which experimental evidence exists, but no all-electron calculation has been reported so far.

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