{
  "abstract": "The General Relativistic Atomic Structure package [{\\sc Grasp}2018, C. Froese Fischer, G. Gaigalas, P. Jönsson, J. Bieroń, Comput. Phys. Commun. (2019), DOI: 10.1016/j.cpc.2018.10.032], is based on multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction (RCI) methods for energy structure calculations. Atomic state function used in the program is built from the set of configuration state functions (CSFs). The valence-valence, core-valence and core-core correlations are explicitly included through expansions over CSFs in RCI. We present a combination of RCI and the stationary second-order Rayleigh-Schrödinger many-body perturbation theory in irreducible tensorial form to account for electron core-valence correlations when an atom or ion has any number of valence electrons. This newly developed method, which offers two ways of use, allows a significant reduction of the CSF space for complex atoms and ions. We also demonstrate how the method and program works for energy structure calculation of Cl III element.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: Lithuanian Journal of Physics, 64, No. 1, 20-39 (2024)",
  "arxiv": "2609.15430",
  "author_total": 3,
  "authors": [
    {
      "name": "G. Gaigalas"
    },
    {
      "name": "P. Rynkun"
    },
    {
      "name": "L. Kitovienė"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/bzwnvww7y6x3n.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.15430",
  "fulltext_url": null,
  "id": "bzwnvww7y6x3n",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.15430",
  "language": null,
  "licence": "CC-BY-NC-ND-4.0",
  "licence_label": "CC BY-NC-ND 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "physics.atom-ph"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.15430",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-14",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/bzwnvww7y6x3n.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:22:19Z",
      "native_id": "2609.15430",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.15430"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.atom-ph",
      "subfield": "amo"
    }
  ],
  "title": "Second-order Rayleigh-Schrödinger Perturbation Theory for the {\\sc Grasp}2018 Package: Core-valence Correlations",
  "title_text": "Second-order Rayleigh-Schrödinger Perturbation Theory for the {\\sc Grasp}2018 Package: Core-valence Correlations",
  "type": "preprint",
  "updated_at": "2026-10-30T12:22:19Z",
  "url": "https://research.draconitic.com/paper/bzwnvww7y6x3n",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.3952/physics.2024.64.1.3",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}