On the performance of energy-consistent spin–orbit pseudopotentials: (111)H revisited

A new two-component relativistic pseudopotential (PP) of the energy-consistent (EC) variety, adjusted to multi-configuration Dirac–Hartree–Fock (MCDHF) data, is presented for the superheavy element 111 and is applied in correlated valence ab initio calculations, with and without inclusion of spin–orbit (SO) coupling, to the determination of spectroscopic constants of the element 111 monohydride. Good agreement with a recent study by Han and Hirao [Chem. Phys. Lett. 328 (2000) 453] is found, and it is concluded that a direct two-component PP fit is superior to a previously practiced two-step (scalar-relativistic/SO) adjustment procedure. We estimate the molecular constants of element 111 monohydride to be Re=1.529 Å, De=2.83 eV and ωe=2642 cm−1.