Determining core electron binding energies with four-component based EOM-CCSD approaches
Résumé
The localized nature of core orbitals makes spectroscopic approaches probing core electrons very selective and sensitive, so that they are capable of providing very accurate information about the chemical surroundings of atoms of interest. At the same time, the complexity of the physical processes taking place in experiment make it very difficult to interpret them without an underlying theoretical framework. In recent years we have witnessed an interest in accurate molecular electronic structure methods such as coupled cluster to provide such a framework. For the most part, these efforts have focused on elements of the first and second rows, for which relatively simple treatments of relativistic effects provides very good results. In this contribution I will present our efforts to enable accurate core spectra calculations for the whole of the periodic table, through our implementation of the core-valence separation approach to the 4-component relativistic Hamiltonian based equation-of-motion coupled-cluster with singles and doubles theory (CVS-EOM-CCSD). I will showcase an initial application to determine core ionization binding energies of halogenated and xenon-containing species, and discuss the relative accuracy of 2-component approaches with respect to a reference 4-component one.