Quasirelativistic 5f-in-core pseudopotential study of the actinocenes An(C8H8)2, An = Th-Pu

Recently developed quasirelativistic energy-consistent 5f-in-core pseudopotentials as well as core-polarization potentials corresponding to tetravalent actinides have been used to study the molecular structures, ionic metal-ring binding energies, and Mulliken orbital populations of the actinocenes An(C8H8)2 (An = Th-Pu). The results of Hartree-Fock calculations show only small deviations from 5f-in-valence calculations, although the 5f orbitals contribute to the covalent actinide-ring bonding. For thorocene and uranocene, second-order Møller-Plesset perturbation theory, coupled-cluster theory with single and double excitation operators and a perturbative estimate of triple excitations, and density functional theory yield actinide-ring distances which are in good agreement with the experimental values.