Heaviest Element Has Unusual Shell Structure

Abstract

Fermion localization functions are used to discuss electronic and nucleonic shell structure effects in the superheavy element oganesson, the heaviest element discovered to date. Spin-orbit splitting in the 7p electronic shell becomes so large (∼10 eV) that Og is expected to show uniform-gas-like behavior in the valence region with a rather large dipole polarizability compared to the lighter rare gas elements. The nucleon localization in Og is also predicted to undergo a transition to the Thomas-Fermi gas behavior in the valence region. This effect, particularly strong for neutrons, is due to the high density of single-particle orbitals. 118 Og, 0.89 þ1.07 −0.31 ms, is too short for chemical "oneatom-at-a-time" studies; hence, its chemical properties must be inferred from advanced atomic calculations based on relativistic quantum theory [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. According to these, Og has a closed-shell ½Rn 5f 14 6d 10 7s 2 7p 6 configuration [13,20,21], with a very large spin-orbit splitting of the 7p shell (9.920 eV at the Dirac-Breit-Hartree-Fock and 10.125 eV at the Fock-space coupled-cluster level; see below). In contrast to its electronic configuration (Og completes the seventh period of the periodic table), it is not expected to behave like a typical rare gas of group 18. For example, the relativistic 7p 3=2 expansion and the relativistic 8s contraction make Og the first rare gas element with a positive electron affinity of 0.064 eV [10,16,22]. This result includes a substantial quantum electrodynamic correction of 0.006 eV [16].Nuclear structure calculations predict 294 Og to be a deformed nucleus [23][24][25][26], eight neutrons away from the next neutron shell closure at 302 Og (N ¼ 184) [27][28][29][30][31][32]. A new factor impacting properties of superheavy nuclei is the strong electrostatic repulsion: The Coulomb force in superheavy nuclei cannot be treated as a small perturbation atop the dominating nuclear interaction; the resulting polarization effects due to Coulomb frustration are expected to influence significantly the proton and neutron

Prediction of stable radon fluoride molecules and geometry optimization using first-principles calculations

“…In the case of many-electron atoms, the relativistic contraction of inner-shell orbitals by screening affects the outer-shell orbitals 28 . This may result in a significant impact on the chemical and physical properties of heavy inert gases in the lower half of the periodic table 29 . Therefore, the relativistic effect of Xe was further considered at the CCSD level using the DKH Hamiltonian.…”

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Figure 3 The bond lengths of RnF 6 including all calculations by the CCSD method. *The calculated values 29 with relativistic effect (Rel) and non-relativistic effect (NR).

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Prediction of stable radon fluoride molecules and geometry optimization using first-principle calculations

“…In the case of many-electron atoms, the relativistic contraction of inner-shell orbitals by screening affects the outer-shell orbitals 26 . This may have a signi cant impact on the chemical and physical properties of heavy inert gases present in the lower half of the periodic table 27 . Therefore, the relativistic effect of Xe was further considered at the CCSD level using the DKH Hamiltonian.…”