Angular coefficients in large-scale atomic structure calculations

Recent calculations on atomic structure and properties have used sets of configurational states (CSFs) of dimension O(10(5)), much larger than was envisaged in the 1970s when programs such as MCHF and GRASP were designed. Current algorithms for reducing matrix elements between open shell CSFs to a sum of Slater integrals account for a substantial part of the computational cost of such calculations. This paper proposes a new approach which aims at major reductions in the resources required.