Examinando por Autor "Alvarez Thon, Luis Rolando"

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    Ítem
    High level relativistic calculations on transition metal complexes
    (Universidad Andrés Bello, 2009) Alvarez Thon, Luis Rolando; Arratia Pérez, Ramiro; Facultad de Ecología y Recursos Naturales
    For calculating properties on molecules that contain heavy elements of the periodic table, only a theory that salves the four-component Dirac equation is suitable. In effect, scalar relativistic effects can stabilize s and p orbitals and destabilize d and f orbitals. In this context bond lengths and other spectroscopic constants can change drastically going from the non-relativistic to the relativistic framework. On the other hand, the spin-orbit effect could change completely the assignment of the ground state of a molecule. This thesis is a study of the Jahn-Teller effect in six heavy transition-metal complexes (RhF6 , WF6 , ReF6 , OsF6 , IrF6 , PtF6). In these complexes, the relativistic effects and electron correlation are large, therefore in order to obtain reliable results, all calculations have been carried out by solving the four-component Dirac equation. Dirac-Hartree-Fock (DHF) and correlated Density Functional Theory (DFT) methods were applied. The use of a four-component code involves a very demanding computational effort and nowadays it is considered a state-of-the-art method. The main results consisted in assigning the ground state and the geometry of the six complexes. Experimentally, the complex PtF6 is essentially diamagnetic ("singlet") and strictly octahedral, but previous theoretical studies had determined that it should distort due the J ahn-Teller effect and that its ground state should be a "triplet". The explanation of this contradiction is that the previous studies did not included the spin-orbit interaction. In contrast, the results in this thesis show unequivocally that PtF 6 is octahedral and that the J ahn-Teller effect is quenched by the spin-orbit effect. The other interesting case is IrF6 , since a non-relativistic or scalar relativistic description would show that this complex is not J ahn-Teller-distorted and must be octahedral, like its isoelectronic counterpart RhF6 . However, the results of this thesis indicate that IrF6 must distort, which is in complete agreement with experimental results. The results conclude that the J ahn-Teller must be studied including the spin-orbit interaction when the systems considered have heavy-metal nuclei. The spin-orbit effect could change the assignment of the ground state of the complexes studied, therefore if the J ahn-Teller effect is applicable in the non-relativistic framework, it could be canceled out in the relativistic one. In general, the criterion usually used to predict the existen ce of the J ahn-Teller effect in molecules with light atomic nuclei, is not valid anymore when the atomic nuclei are heavy.