Solid Oganesson via a Many-Body Interaction Expansion Based on Relativistic Coupled-Cluster Theory and from Plane-Wave Relativistic Density Functional Theory

Abstract

Many-body potentials up to fourth order are constructed using nonrelativistic, scalar-relativistic, and relativistic coupled-cluster theory to accurately describe the interaction between superheavy oganesson atoms. The obtained distance-dependent energy values were fitted to extended two-body Lennard-Jones and three-body Axilrod− Teller−Muto potentials, with the fourth-order term treated through a classical long-range Drude dipole interaction model. From these interaction potentials, spectroscopic constants for the oganesson dimer and solid-state properties were obtained. Furthermore, these high-level results are compared to scalarrelativistic and two-component plane-wave DFT calculations based on a tailor-made projector augmented wave pseudopotential (PAW-PP) and newly derived parameters for Grimme's dispersion correction. It is shown that the functionals PBE-D3(BJ), PBEsol, and in particular SCAN provide excellent agreement with the many-body reference for solid oganesson. Finally, the results for oganesson are compared and related to the lighter rare gas elements, and periodic trends are discussed.

Copernicium: A Relativistic Noble Liquid

“…In this respect, Cn is much more similar to the noble gas Rn (band gap 7.1 eV) than to its lighter congeners, and even more similar to Rn than oganesson (Og) as the actual Group 18 member of the seventh period (band gap 1.5 eV, see Figure c) . Together with the smaller cohesive energy of Cn (0.38 eV vs. 0.45 eV), this suggests that Cn is more noble‐gas‐like than Og.…”

“…However, the relatively strong interaction with the gold surface may as well be due to strong dispersion interactions. Also considering the distinctly larger cohesive energy of the superheavy “noble gas” oganesson (Og) of −0.45 eV, Cn appears to lean towards the noble gases rather than towards its lighter metallic congeners.…”

Oganesson Is a Semiconductor: On the Relativistic Band‐Gap Narrowing in the Heaviest Noble‐Gas Solids

“…Experimental structures were used for Ne to Xe, and for Rn and Og high‐level computational structures were employed (cf. Table SII, Supporting Information) . The core region was modeled using the projector‐augmented wave (PAW) approach of Joubert and Kresse with the potentials for He to Rn taken from the VASP library .…”

“…[16],w ew ill focus here on the evolution of DE, O g ,a nd E g with increasing atomic number.B ys imple extrapolation based on Figure 2, one would anticipate aneardegeneracyofthe three at about 7eVfor Rn, and values just above 4eVf or Og, placing the latter at the borderline between insulators and semiconductors.H owever,s uch as imple extrapolation disregards that the close resemblance between atomic and bulk properties may break in the heavier noble gases which are larger,m ore polarizable and thus interact more strongly.This is reflected in the cohesive energy (E coh ,b inding energy of the solid per atom, red line in Figure 2), which increases continuously to 0.23 eV for Rn, and jumps to 0.45 eV for Og. [19,20] Hence,O gi sb yf ar the least noble of the noble gases,l ess noble even than superheavy copernicium (Cn, E coh = 0.38 eV) [22][23][24] and thus presumably also as olid at ambient conditions.A ccordingly,e xcitons in solid Og and perhaps also Rn may exhibit adelocalization and stabilization compared to the respective excited states of the atoms,w hich could cause O g and E g to fall well below DE, breaking with the periodic trends and rendering Og as emiconductor.…”

“…Inspection reveals that as expected, DFT affords much too small band gaps which improve slightly with SCANa nd HSE06 compared to PBE. However,e ven with these modern functionals,t he predicted band gaps of the noble-gas solids are more similar to those [17] and electronic E g (black) band gaps [16] as well as cohesive energies (red, secondary axis) [18][19][20] of the respective solids. Data for He-Rn from experiment, and for Og (E coh also Rn) from coupled-cluster calculations.…”