Abstract
The quest to discover new elements, explore their properties, and rationalize periodical trends is as old as chemistry, dating back to the era of Mendeleiev
and Meyer. More recently, due to their peculiar electronic structure and prominent positions in the periodic table, superheavy elements like Copernicium
(Z = 112), Flerovioum (114), and Oganesson (118) have moved into the focus. In early theoretical work, Pitzer recognized the decisive impact of relativistic
effects on Cn and FI, inferring a noble-gas-like character [1]. Three decades later, based on the interactions with a gold surface in atom-at-a-time
experiments, Eichler and coworkers suggesteda Cn to bea metallic solid [2]. This talk describes our journey to unravel the riddle of Cn and shed some light
on the physicochemical properties of superheavy main-group elements through first-principles calculations. To this end, I will
begin with a glance at the developed methodology, which combines new pseudopotentials and DFT-D3 parameters for
elements 112-118 [3] to perform (non-) relativistic free-energy calculations [4]. After establishing that our approach accurately
reproduces the melting and boiling points of the known Group 12 elements [5], application to Cn provides a liquid range from -50°C to about
90°C, in line with Pitzer's hypothesis. Further, we find that a large electronic band gap of 6.4eV (self-consistent GW level of theory)
distinguishes Cn from its lighter metallic congeners [4] and confirms that it isa “noble liquid", held together by dispersion
forces [1]. In light of these results, we argue that Cn challenges Og forits noble status, which is corroborated by studies on Og: Witha melting point of -50°C
and band gap of 1.5 eV, Og is neither noble nora gas [6,7] but a solid semiconductor. Lastly, I will briefly discuss FI, whose spin-orbit-induced
pseudo-closed shell configuration renders it elusive to our first-principles free-energy approach.
References
[1] K. Pitzer, JCP (1975), 63, 1032
[2] R. Eichler et al., ANIE (2008), 47, 3262 (2008).
[3] L. Trombach, S. Ehlert, S. Grimme, P. Schwerdtfeger, J. Mewes, PCCP (2019), 21, 18048
[4] J. Mewes, O. Smits, G. Kresse, P. Schwerdtfeger, ANIE (2019), 58, 17964
[5] J. Mewes, P. Schwerdtfeger, ANIE (2021), 60, 7703
[6] J. Mewes, P. Jerabek, O. Smits, P. Schwerdtfeger, ANIE (2019), 58, 14260
[7] O. Smits, J. Mewes, P. Jerabek, P. Schwerdtfeger, ANIE (2020), 59, 23636
