Ground and excited states of PtCH2+: assessment of the no-pair Douglas–Kroll ab initio model potential method

Abstract

Relativistic all-electron and ab initio model potential (AIMP) calculations have been performed on the PtCH₂⁺ ground and low-lying excited states employing a one-component Hamiltonian. Electron correlation is taken into account by means of a multireference configuration interaction treatment whereas spin–orbit coupling effects have been added as a perturbation. The no-pair Douglas–Kroll ab initio model potential method is found to reproduce all-electron results excellently. The one-center spin–orbit mean-field Douglas–Kroll ab initio model potential approach appears to be a competitive means for electronic structure calculations on compounds containing heavy elements. An analysis of the PtCH₂⁺ electronic ground state structure reveals that both the Pt⁺ configurations d⁹ and d⁸s¹ participate in the double bond. This finding differs to some extent from a model postulating that a d⁸s¹ structure is preferred.