[PDF]    https://doi.org/10.3952/physics.2024.64.1.3

Open access article / Atviros prieigos straipsnis
Lith. J. Phys. 64, 20–39 (2024)

SECOND-ORDER RAYLEIGH–SCHRÖDINGER PERTURBATION THEORY FOR THE GRASP2018 PACKAGE: CORE–VALENCE CORRELATIONS*
Gediminas Gaigalas, Pavel Rynkun, and Laima Kitovienė
Institute of Theoretical Physics and Astronomy, Vilnius University, Saulėtekio 3, 10257 Vilnius, Lithuania
Email: gediminas.gaigalas@tfai.vu.lt; pavel.rynkun@tfai.vu.lt; laima.radziute@tfai.vu.lt

Received 31 July 2023; accepted 4 August 2023

The General Relativistic Atomic Structure package [GRASP2018, C. Froese Fischer, G. Gaigalas, P. Jönsson, and 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. The 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 an 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 the energy structure calculation of Cl III ion.
Keywords: configuration interaction, configuration state function generators, spin-angular integration, perturbation theory, tensorial algebra, core–valence correlations
PACS: 31.15.-p, 31.15.Ne, 31.30.Jv, 03.65.Pm

* Dedicated to the memory of professor Adolfas Jucys (1904–1974), pioneer of contemporary theoretical physics in Lithuania, initiator of the ‘Lithuanian Physics Collection’, on the occasion of his birth and death anniversaries.

ANTROSIOS EILĖS RELĖJAUS IR ŠRĖDINGERIO TRIKDYMŲ TEORIJA GRASP2018 PROGRAMINIAM PAKETUI: KAMIENO IR VALENTINĖS KORELIACIJOS*
Gediminas Gaigalas, Pavel Rynkun, Laima Kitovienė

Vilniaus universiteto Teorinės fizikos ir astronomijos institutas, Vilnius, Lietuva
GRASP programinis paketas [GRASP2018, C. Froese Fischer, G. Gaigalas, P. Jönsson, J. Bieroń, Comput. Phys. Commun. (2019), DOI: 10.1016/j.cpc.2018.10.032] grindžiamas daugiakonfigūraciniu Dirako, Hartrio ir Foko bei reliatyvistiniu konfigūracijų superpozicijos (RCI) metodais, skirtais atomų ir jonų energijos struktūros skaičiavimams. Programoje naudojama atominė būsenos funkcija sudaryta iš konfigūracinių būsenų funkcijų rinkinio. RCI metode valentinės-valentinės, kamieno-valentinės ir kamieno-kamieno koreliacijos yra tiesiogiai įtrauktos į atomo būsenos funkciją per konfigūracinių būsenų funkcijas. Šiame darbe pateiktas naujas efektyvesnis kamieno-valentinių koreliacijų įskaitymo būdas. Jis sukurtas remiantis RCI ir stacionarios daugiadalelės trikdžių teorijos neredukuotinėje tenzorinėje formoje kombinacija. Tai leidžia įskaityti kamieno-valentines koreliacijas, naudojant trikdžių teoriją bet kokiam atomui ir jonui su bet kokiu valentinių elektronų skaičiumi. Šis naujai sukurtas metodas, kurį galima naudoti dviem būdais, leidžia gerokai sumažinti konfigūracinių būsenų funkcijų erdvę sudėtingiems atomams ir jonams, kas daug lengviau leidžia išplėsti GRASP programinio paketo galimybes. Darbe pademonstruota, kaip šis metodas veikia apskaičiuojant Cl III jono energijos struktūrą.

* Skiriama šiuolaikinės teorinės fizikos Lietuvoje pradininko, „Lietuvos fizikos rinkinio“ iniciatoriaus akad. Adolfo Jucio (1904–1974) gimimo ir mirties sukaktims paminėti.


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