Physics in Screening Environments
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In the current study, we investigated atoms in screening environments likeplasmas.It is common practice to extract physical data, such as temperature andelectron densities, from plasma experiments. We present results that addressinherent computational difficulties that arise when the screening approach isextended to include the interaction between the atomic electrons. We show thatthere may arise an ambiguity in the interpretation of physical properties, suchas temperature and charge density, from experimental data due to the opposingeffects of electron-nucleus screening and electron-electron screening.The focus of the work, however, is on the resolution of inherent computationalchallenges that appear in the computation of two-particle matrix elements.Those enter already at the Hartree-Fock level. Furthermore, asexamples of post Hartree-Fock calculations, we show second-order Green'sfunction results and many body perturbation theory results of second order.A self-contained derivation of all necessary equations has been included. Theaccuracy of the implementation of the method is established by comparingstandard unscreened results for various atoms and molecules against literaturefor Hartree-Fock as well as Green's function and many body perturbationtheory.The main results of the thesis are presented in the chapter called ScreenedResults, where the behavior of several atomic systems depending onelectron-electron and electron-nucleus Debye screening was studied.The computer code that we have developed has been made available for anybody touse.Finally, we present and discuss results obtained for screened interactions. Wealso examine thoroughly the computational details of the calculations andparticular implementations of the method.