Electronic structures of PtCu, PtAg, and PtAu molecules: a Dirac four-component relativistic study

Relativistic four-component calculations at several correlated levels have been performed for diatomic PtCu, PtAg, and PtAu molecules. The ground state spectroscopic constants of PtCu were calculated using the four-component MP2 method, and show good agreement with experiment. We also performed calculations on the experimentally unknown species, PtAg and PtAu, and the mono-cationic systems, PtCu+, PtAg+, and PtAu+. The low-lying excited states of these diatomic molecules were also investigated using the four-component multi-reference CI method