Two-program package to calculate the ground and excited state wave functions in the Hartree—Fock—Dirac approximation Original Research Article

Algorithms and computer codes to calculate the ground and excited (discrete and continuum) state wave functions of many-electron atoms and ions, including those containing positive/negative muons, in the Hartree—Fock—Dirac (HFD) approximation are reported. In contrast to the usual technique, the system of 2S self-consistent first order integro-differential equations of the HFD is solved by reducing it first to a system of S second order ones. The latter is then treated numerically by means of successive iterative refinement of both the orbital wave functions and the one-electron energies. Some improvements are incorporated into the codes to speed up the convergence process in the cases of large exchange coefficients, as well as to take nuclear size effects into account. The program enables one to find the self-consistent solution of the problem in the form of a single determinant or a linear combination of such determinants constructed from the one-electron orbitals corresponding to the specific configuration and the term of the atom/ion. The code is written in Fortran and can be run on any platform for which the corresponding compiler is available.