A general program for computing angular integrals of the Breit–Pauli Hamiltonian with non-orthogonal orbitals Original Research Article

The BREIT_NO program performs the angular integrations necessary for expressing the matrix elements of the Breit–Pauli Hamiltonian as a linear combination of radial integrals. Any amount of non-orthogonality between the orbitals may be present leading to overlap factors in the matrix elements. The calculations follow the method based on the representation of configuration wave functions through the Slater determinants. All matrix elements for a given list of configuration states may be evaluated or for a selected subset. The program effectively reuses data obtained previously through the creation of a data bank for angular coefficients.