27. 11. 2012. Seminar: Ljiljana Stojanović

Tuesday, 27 November 2012 at 3PM
IPB Library

Ljiljana Stojanović
Faculty of Physical Chemistry

Theoretical Study of Hyperfine Interactions in Arsenic Radicals

Abstract:

The interaction between spin of unpaired electron and nuclear spins, known as hyperfine interaction, induces specific structure of EPR spectra that are useful for study of radicals. Distribution of the unpaired electron spin density is affected by numerous effects, which makes its calculation by means of quantum chemical methods quite complicated. Hence, hyperfine interactions have been studied only in radicals containing light elements. In this study, DFT and wave-function-based methods were employed to study arsenic's isotropic and anisotropic hyperfine parameters in AsH2, H2AsO, and AsO2. The applicability of the particular method depends on mechanism of hyperfine interactions in each concrete case.

The mechanisms of hyperfine interactions were studied by examining orbital contributions to spin density. The spin polarization mechanism in AsH2 was studied by evaluating one- and two-electron integrals in spin-restricted and unrestricted case. Studied mechanism differs substantially from the classical model based on exchange interactions between the unpaired electron and same-spin electrons from occupied orbitals. In this case, spin polarization of doubly occupied orbitals in core region is induced by their exchange interactions with other doubly occupied same-spin orbitals. Applying scalar-relativistic DKH2 DFT methods, it was found that relativistic effects induce shifting of the spin density toward arsenic, enhancing hyperfine interactions.