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

Abstract

Oganesson (Og) is the most recent addition to Group 18. Investigations of its atomic electronic structure have unraveled a tremendous impact of relativistic effects, raising the question whether the heaviest noble gas lives up to its position in the periodic table. To address the issue, we explore the electronic structure of bulk Og by means of relativistic Kohn–Sham density functional theory and many‐body perturbation theory in the form of the GW method. Calculating the band structure of the noble‐gas solids from Ne to Og, we demonstrate excellent agreement for the band gaps of the experimentally known solids from Ne to Xe and provide values of 7.1 eV and 1.5 eV for the unknown solids of Rn and Og. While this is in line with periodic trends for Rn, the band gap of Og completely breaks with these trends. The surprisingly small band gap of Og moreover means that, in stark contrast to all other noble‐gas solids, the solid form of Og is a semiconductor.

Copernicium: A Relativistic Noble Liquid

“…This similarity further extends to the electronic band gap. Accurate many-body perturbation theory in the form of the self-consistent quasi-particle GW method [20,33,34] affords aband gap of 6.4 AE 0.2 eV for Cn (hcp), clearly characterizing it as an insulator (see the Supporting Information for details on the calculations). 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,s ee Figure 3c).…”

“…Calculations for Hg, Cn, and Group 18 at the SO-GW level of theory as described in the SupportingInformation and Ref. [20] (Group 18). and boiling points by 300 Ka nd 700 K. Hence,t he liquid aggregate state as well as the weakly interacting nature of Cn are both due to relativistic effects or, in other words,C ni s arelativistic noble liquid.…”

Copernicium: A Relativistic Noble Liquid

“…Calculations for Hg, Cn, and Group 18 at the SO‐GW level of theory as described in the Supporting Information and Ref. (Group 18).…”

“…This similarity further extends to the electronic band gap. Accurate many‐body perturbation theory in the form of the self‐consistent quasi‐particle GW method affords a band gap of 6.4±0.2 eV for Cn ( hcp ), clearly characterizing it as an insulator (see the Supporting Information for details on the calculations). 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) .…”

“…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.…”