Relativistic Calculation of Magnetic Properties of Molecules
Lucas Visscher
Department of Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083,
NL-1081 HV Amsterdam, The Netherlands
In this talk I will consider the use of the 4-component Dirac equation in
electronic structure calculations. Substituting the Schrödinger equation by
the Dirac equation in quantum chemical methods provides an unique way of
incorporating both scalar relativistic and spin-orbit effects in the
calculation. It also gives rise to a number of interesting conceptual
differences with non-relativistic theory. Two examples that will be
discussed are the calculation and interpretation of spin-orbit effects and
the calculation of the diamagnetic contributions to NMR parameters.
We are now entering the stage where routine application of 4-components
methods to molecular systems is only limited by the large computational
resources required and the lack of efficient implementations for some of
the post-Hartree-Fock methods. I will first discuss the computational
scaling of the various 4-component methods in comparison with both
non-relativistic and more approximate relativistic methods. After that I
will give an overview of the strategies that can be followed to overcome
the remaining computational bottlenecks.
In the applications section I will focus mainly on the calculations of NMR
parameters as these parameters are determined by the shape of the wave
function near the nuclei and are hence heavily influenced by relativistic
effects.