Generalized relativistic small‐core pseudopotentials accounting for quantum electrodynamic effects: Construction and pilot applications

A simple procedure to incorporate one‐loop quantum electrodynamic (QED) corrections into the generalized (Gatchina) nonlocal shape‐consistent relativistic pseudopotential model is described. The pseudopotentials for Lu, Tl, and Ra replacing only inner core shells (with principal quantum numbers n ≤ 3 for the two former elements and n ≤ 4 for the latter one) are derived from the solutions of reference atomic SCF problems with the Dirac–Coulomb–Breit Hamiltonian to which the model Lamb shift operator added. QED contributions to atomic valence excitation energies evaluated at the SCF level are demonstrated to exceed the errors introduced by the pseudopotential approximation itself by an order of magnitude. Pilot applications of the new model to calculations of excitation energies of two‐valence‐electron atomic systems using the intermediate‐Hamiltonian relativistic Fock space coupled cluster method reformulated here for incomplete main model spaces are reported. Implications for high‐accuracy molecular excited state calculations are discussed. The incorporation of quantum electrodynamic corrections (self‐energy and vacuum polarization) into the generalized (nonlocal) shape‐consistent relativistic pseudopotentials of small atomic cores gives rise to a highly accurate electronic structure model of heavy element atoms and compounds. Combined with the electron correlation treatment using the new formulation of intermediate‐Hamiltonian relativistic Fock space coupled cluster method, this model offers the possibility of precision calculations on electronic excitations in atoms and molecules.