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arXiv · 2609.16761

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

G. Gaigalas·P. Rynkun·L. Kitovienė
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Abstract

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) (https://doi.org/10.3952/physics.2024.64.1.3), 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.

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G. Gaigalas, P. Rynkun, L. Kitovienė. 2026-09-15. Second-Order Rayleigh-Schrödinger Perturbation Theory for the GRASP2018 Package: Core Correlations. https://doi.org/10.3952/physics.2024.64.2.1

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