Relativistic Quantum Chemistry with Pseudopotentials and Transformed Hamiltonians

Institute of Physical and Theoretical Chemistry, Rheinische Friedrich-WUhelms-Universitat Bonn 

Relativistic effects in atoms and molecules are commonly separated in kinematical effects, which do not cause a splitting of energy levels due to the spin degrees of freedom, and the effects of spin-orbit coupling. This separation is not unambiguously defined (Visscher and van Lenthe 1999), but is nevertheless extremely convenient when discussing effects on phenomenology. 

Kinematical relativistic effects are caused by the fact that in the vicinity of the nucleus the electrons acquire high velocities, at a substantial fraction of the velocity of light. The direct influence of the relativistic kinematics (the so-called direct relativistic effect) is thus largest in the vicinity of the nucleus. However, as far as their impact on chemistry is concerned, relativistic effects are most important in the valence shells, which despite the small velocities of outer electrons are still strongly affected by relativistic kinematics (Schwarz et al. 1989). In particular, valence s and p orbitals possess inner tails they are core-penetrating orbitals, which means that there is a nonvanishing probability of finding their electrons close to the nucleus and thus 

Relativistic Effects in Heavy-Element Chemistry and Physics. Edited by B. A. Hess 2003 John Wiley Sons Ltd 

This destabilization may lead, in turn, to an indirect stabilization of the next higher s and p shells with spatial extent similar to the d shell in question. This situation occurs in the case of the late transition metals and leads to the gold maximum of relativistic effects and the unusually large relativistic effects in the elements of groups 10-12. If the d shell is only weakly occupied, as is the case in the early transition metals, the direct effect on the s and p shells is partly balanced by the indirect effect on those shells, and the relativistic effects are generally much smaller. 

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Hess, B. A. Dolg, M. Relativistic Quantum Chemistry with Pseudopotentials and Transformed Hamiltonians, Relativistic Effects in Heavy-Element Chemistry and Physics -, Ed. Hess, B. A. Wiley Chichester, 2002, pp. 89-122. 

Relativistic Quantum Chemistry with Pseudopotentials and Transformed Hamiltonians... 

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