51/ algebra atom-field interaction

One feature of relativistic self-consistent field calculations to which attention should be drawn is the fact that the Breit interaction can be easily included in the self-consistent field iterations once the algebraic approximation has been invoked. This should be contrasted with the situation in atomic calculations using numerical methods in which the Breit interaction is treated by first-order perturbation theory. 

It has not been possible within the space available to give a completely comprehensive account of all of the developments which have recently been made in the field of basis set construction, a field that forms the foundation upon which the vast majority of contemporary atomic and molecular electronic structure studies are based. This review has necessarily been selective but should provide the reader with an up-to-date account of the most important aspects of current thinking on the algebraic approximation. It has concentrated on the construction of basis sets for electron correlation energy calculations, for calculations of atomic and molecular properties (other than the energy), for the study of small interaction energies such as van der Waals interactions, for the determination of relativistic effects and for studies of extended molecular systems. 

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