Scalar-relativistic/spin-free potential

The restriction to scalar terms and hence to a one-component Hamiltonian is sometimes referred to as a spin averaged formulation. However, the names spin-free or scalar relativistic formulation seem to be more appropriate. The matrix representations of all terms occurring after these manipulations are already available within every quantum chemical program package except for the PVP expressions. Their evaluation can, however, be reduced to the representation of the external potential via the relation... 

In 1974 Walecka [Wa 74] introduced the first relativistic quantum field theory for nuclear matter. The mesonic degrees of freedom included scalar and vector fields. This model, referred to as the quantum hadrodynamic (QHD) model, accounts for spin-orbit splitting in the shell model and the ground state properties of many nuclei [Se 85]. Noble [No 79] demonstrated the consistency between the strengths of the scalar and vector potentisds in Walecka s QHD theory and those obtained from relativistic one-meson exchange potentials for the free NN interaction. 

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