Browsing by Author "Smits OR"

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    Oganesson: A Noble Gas Element That Is Neither Noble Nor a Gas
    (Wiley-VCH GmbH, 2020-12-21) Smits OR; Mewes J-M; Jerabek P; Schwerdtfeger P
    Oganesson (Og) is the last entry into the Periodic Table completing the seventh period of elements and group 18 of the noble gases. Only five atoms of Og have been successfully produced in nuclear collision experiments, with an estimate half-life for ²⁹⁴⁄₁₁₈ Og of 0. 69⁺⁰‘⁶⁴⁄⁻₀¸₂₂ ms.⁽¹⁾ With such a short lifetime, chemical and physical properties inevitably have to come from accurate relativistic quantum theory. Here, we employ two complementary computational approaches, namely parallel tempering Monte-Carlo (PTMC) simulations and first-principles thermodynamic integration (TI), both calibrated against a highly accurate coupled-cluster reference to pin-down the melting and boiling points of this super-heavy element. In excellent agreement, these approaches show Og to be a solid at ambient conditions with a melting point of ≈325 K. In contrast, calculations in the nonrelativistic limit reveal a melting point for Og of 220 K, suggesting a gaseous state as expected for a typical noble gas element. Accordingly, relativistic effects shift the solid-to-liquid phase transition by about 100 K.
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    Pushing the limits of the periodic table — A review on atomic relativistic electronic structure theory and calculations for the superheavy elements
    (Elsevier B.V., 2023-10-13) Smits OR; Indelicato P; Nazarewicz W; Piibeleht M; Schwerdtfeger P; Schwenk A
    We review the progress in atomic structure theory with a focus on superheavy elements and their predicted ground state configurations important for an element's placement in the periodic table. To understand the electronic structure and correlations in the regime of large atomic numbers, it is essential to correctly solve the Dirac equation in strong Coulomb fields, and to take into account quantum electrodynamic effects. We specifically focus on the fundamental difficulties encountered when dealing with the many-particle Dirac equation. We further discuss the possibility for future many-electron atomic structure calculations going beyond the critical nuclear charge Zcrit≈170, where levels such as the 1s shell dive into the negative energy continuum (Enκ<−mec2). The nature of the resulting Gamow states within a rigged Hilbert space formalism is highlighted.