Small-core multiconfiguration-Dirac–Hartree–Fock-adjusted pseudopotentials for post-<b> <i>d</i> </b> main group elements: Application to PbH and PbO

Relativistic pseudopotentials (PPs) of the energy-consistent variety have been generated for the post-d group 13–15 elements, by adjustment to multiconfiguration Dirac–Hartree–Fock data based on the Dirac–Coulomb–Breit Hamiltonian. The outer-core (n−1)spd shells are explicitly treated together with the nsp valence shell, with these PPs, and the implications of the small-core choice are discussed by comparison to a corresponding large-core PP, in the case of Pb. Results from valence ab initio one- and two-component calculations using both PPs are presented for the fine-structure splitting of the ns2np2 ground-state configuration of the Pb atom, and for spectroscopic constants of PbH (X 2Π1/2, 2Π3/2) and PbO (X 1Σ+). In addition, a combination of small-core and large-core PPs has been explored in spin-free-state shifted calculations for the above molecules.