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** Molecular modeling calculations **

** Molecular orbital calculations **

It is important to emphasize that this comparison of molecular orbital calculations and experimental spectra is qualitative, as the limitation to a single molecule and the intrinsic precision of the computational approach used do not allow a quantitative comparison. Nevertheless, the characteristics of the orbitals, such as the electron density distribution, are very similar for different density functional and semiempirical calculations, indicating that the calculations are useful for a qualitative interpretation of the spectra. Detailed electronic structure calculations have been recently applied to the understanding of intermolecular magnetic interaction pathways in nitroxide radicals [43], underlining the importance of comparisons between computational data and spectroscopic results which provide a quantitative test for the theoretical models. [Pg.108]

Valence band spectra provide information about the electronic and chemical structure of the system, since many of the valence electrons participate directly in chemical bonding. One way to evaluate experimental UPS spectra is by using a fingerprint method, i.e., a comparison with known standards. Another important approach is to utilize comparison with the results of appropriate model quantum-chemical calculations 4. The combination with quantum-chcmica) calculations allow for an assignment of the different features in the electronic structure in terms of atomic or molecular orbitals or in terms of band structure. The experimental valence band spectra in some of the examples included in this chapter arc inteqneted with the help of quantum-chemical calculations. A brief outline and some basic considerations on theoretical approaches are outlined in the next section. [Pg.388]

** Molecular modeling calculations **

** Molecular orbital calculations **

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