RELATIVISTIC MANY-BODY PERTURBATION-THEORY CALCULATIONS ON KR - ACCURATE REPRESENTATION OF 2ND-ORDER AND 3RD-ORDER ENERGIES WITH CONTRACTED GAUSSIAN-BASIS SET

Relativistic many-body perturbation-theory calculations on Kr have been performed with basis sets of contracted and uncontracted Gaussian-type functions. Second- and third-order Coulomb correlation corrections were computed by systematically enlarging the virtual space. The contracted Gaussian basis sets used in the many-body study are designed to retain flexibility for correlated calculations both in the core and the valence region. They reproduce second- and third-order energy corrections computed with uncontracted Gaussian basis sets to an accuracy of over 99.9%. This type of contraction has the advantage that it reduces integral storage requirements and the time needed for correlated calculations, while retaining high accuracy. Non-additive contributions, due to the interference between relativity and the Coulomb correlation in the second-order correlation energy correction in Kr, is almost-equal-to 0.013 au, an order of magnitude larger than in Ar.