Second-Order Rayleigh-Schrödinger Perturbation Theory for the GRASP2018 Package: Core Correlations

RESUMO

The paper presents a further development of the method G. Gaigalas, P. Rynkun, L. Kitovienė, Second-Order of Rayleigh-Schrödinger Perturbation Theory for the {\sc Grasp}2018 Package: Core-Valence Correlations, {\em Lithuanian Journal of Physics}, 64, No. 1, 20-39 (2024) ( this https URL ), based on a combination of the relativistic configuration interaction method and on the stationary second-order Rayleigh-Schrödinger many-body perturbation theory in an irreducible tensorial form. In this extension the perturbation theory accounts for both electron core-valence and core correlations when an atom or ion has any number of valence electrons meanwhile relativistic configuration interaction accounts for the rest of correlations. This allows a significant reduction of the space of the configuration state function for complex atoms and ions. We also demonstrate how this method works for energy structure calculation of Fe XV ion.