Calculations of the EPR g -tensor using unrestricted two- and four-component relativistic approaches within the HF and DFT frameworks.

Approaches and programs for calculations of the EPRg-tensor in the framework of the two- and four-component methods are still very rare. There are three main reasons for this: the wider community's unawareness of the importance of second- and higher order spin–orbit effects on theg-tensor, the methodological problems associated with performing such calculations and the lack of understanding of these problems. This paper reports on the implementation of a method for calculation of theg-tensor in the framework of the relativistic unrestricted two- and four-component Hartree–Fock and density functional theory approaches based on the Kramers pair formalism. This implementation allows us to analyse problems which arise when theg-tensor is calculated via Kramers pairs in the unrestricted framework. [ABSTRACT FROM AUTHOR]