A relativistic structure model for heavy atoms

An ansatz for the calculation of the structure of heavy atoms using a relativistic model is described and developed. After using a series of Dirac-Fock calculations to define a suitable set of single-particle states, the set of orbitals is Schmidt orthogonalised and the one- and two-body Hamiltonian matrix elements calculated. This list of matrix elements is then processed and redefined to eliminate any reference to the inner electrons which are assumed to constitute a fixed core. These matrix elements are then utilised for large-dimension configuration-interaction calculations using Slater determinants as the basis functions. As an example, the ansatz is applied to the calculation of the low-lying states of Pb I and demonstrate the importance of configuration mixings within the ground-state manifold.