Molecular complexes of the heaviest transition metals are interesting due to their applications in catalysis and nanostructured materials. For understanding details of the associated reaction mechanisms and analyzing spectroscopic observations it is therefore desirable to develop quantum chemical methods that can provide estimates of reaction barriers and excitation energies with quantitative accuracy. This demands a rigorous treatment of both relativistic and electron correlation effects. With the advent of eXact 2-Component (X2C) relativistic methods1, all-electron treatments that include both scalar relativistic effects and spin-orbit coupling effects from the outset have become much more practical, leaving the electron-correlation stage of the calculation as the rate determining step.By treating some recent applications of relativistic coupled-cluster theory I will discuss the current status of these techniques in comparison with other methods like multireference perturbation theory, multireference configuration interaction and density functional theory. I will focus on excitation energies but also discuss the application of relativistic electronic structure methods to molecular properties, in particular those properties that are strongly influenced by relativistic effects such as nuclear quadrupole coupling constants, NMR shieldings and M�ssbauer istope shifts.References 1 K. Dyall, J. Chem. Phys. 106  (1997) 9618. M. Ilia�, H. J. A. Jensen, V. Kell�, B. O. Roos, and M. Urban, Chem. Phys. Lett. 408  (2005) 210. W. Kutzelnigg and W. Liu, J. Chem. Phys. 123  (2005) 241102. M. Filatov, J. Chem. Phys. 125  (2006) 107101. W. Kutzelnigg and W. Liu, J. Chem. Phys. 125  (2006) 107102. M. Ilia� and T. Saue, J. Chem. Phys. 126  (2007) 064102. J. Sikkema, L. Visscher,T. Saue, M. Ilias?, J. Chem. Phys. 131 (2009) 124116.

Relativistic electron correlation methods: Applications to heavy element chemistry and spectroscopy

247th National Meeting (2014)

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