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

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 d(9) and d(8)s(1) participate in the double bond. This finding differs to some extent from a model postulating that a d(8)s(1) structure is preferred.