Recent developments in multiconfigurational perturbation theory and applications in bioinorganic chemistry: An alternative to DFT?

PHYS 216

Kristine Pierloot, Kristin.Pierloot@chem.kuleuven.be, Department of Chemistry, University of Leuven, Celestijnenlaan 200F, box 2404, Leuven, 3001, Belgium
Within bio-inorganic chemistry, DFT (density functional theory) has today become the standard method for solving standard electronic structure problems and modelling processes involving transition metals (TM). However, when it comes to electronically more complicated situations, this method has been shown to be afflicted with quite severe errors. An alternative may be provided by the ab initio CASPT2 method (perturbation theory based on a multiconfigurational reference wave function). The latter method has recently been extended with some important new features (CD-CASPT2, RASPT2) making it more practical and suitable for calculations on extended systems involving more than a thousand basis functions.

In this lecture we will provide a short overview of the new developments in the CASPT2 method. The method will be illustrated and compared to DFT for a number of Fe(II) model systems as well as for important model systems for metallo-enzymes with iron (spin state energetics in ferrous porphyrins1,2; bonding of CO, NO and O2 in myoglobin) and copper (relative energy of the alternative bis-(μ-oxo) and μ-η22 peroxo isomers of supported [Cu2O2]2+ cores in e.g. hemocyanin3). We will also focus briefly on the first applications of our recently implemented method for obtaining EPR g values for TM systems based on multi state CASPT2 calculations4,5.

References:

(1) K. Pierloot, S. Vancoillie, J. Chem. Phys. 125, 124303 (2006); (2) K. Pierloot, S. Vancoillie, J. Chem. Phys. 128, 034104 (2008); (3) P.- Malmqvist, K. Pierloot, A. Rehaman Moughal, C. J. Cramer, L. Gagliardi, submitted; (4) S. Vancoillie, P.- Malmqvist, K. Pierloot, ChemPhysChem 8, 1803-1825 (2007); (5) S. Vancoillie, K. Pierloot. J. Phys.Chem. A (2008), in press.