Numerical Dirac-Fock Calculations for Atoms

Abstract

If judged from the number of papers dealing with the subject, the interest in relativistic corrections to the theoretical determination of electronic properties of atoms, molecules and solids has been growing up very rapidly during the last years. There is much to be said for explaining it: increase in the experimental accuracy especially when dealing with heavy atoms, access to more exotic systems like very stripped ions, theoretical developments which make pratical calculations manageable, availability of fast computers, etc… But despite (or because !) the fact that the importance of relativistic effects is now well established and that sophisticated models have been built up to handle them, it is necessary to question the validity and accuracy of these calculations. This question is not a simple one because of the complexity of the problem. To perform these calculations we have, as everyone knows, to use an approximate Hamiltonian and there is still questions concerning the most appropriate choice of it. Furthermore, as we try to improve our methods, we have to worry more and more about various contributions. Examples are: QED corrections, finite size of the nucleus or non additivity of relativistic and many-body effects.