A Hundred‐Year‐Old Experiment Re‐evaluated: Accurate Ab Initio Monte Carlo Simulations of the Melting of Radon

Abstract

State-of-the-art relativistic coupled-cluster theory is used to construct many-body potentials for the noble-gas element radon to determine its bulk properties including the solid-to-liquid phase transition from parallel tempering Monte Carlo simulations through either direct sampling of the bulk or from a finite cluster approach. The calculated melting temperature are 200(3) K and 200(6) K from bulk simulations and from extrapolation of finite cluster values, respectively. This is in excellent agreement with the often debated (but widely cited) and only available value of 202 K, dating back to measurements by Gray and Ramsay in 1909.

Colloquium : Superheavy elements: Oganesson and beyond

“…Recently, using parallel tempering Monte-Carlo simulations within a many-body expansion for the atomic interaction potential (Smits et al, 2018), it was possible to confirm the melting temperature of T m = 202 K of 222 Rn originally measured in 1909 (Gray and Ramsay, 1909). Preliminary simulations suggest T m ≈ 320 K for Og (Smits et al, 2018). For Cn and Fl, many-body effects in the interaction potential are so important that melting simulations become prohibitively expensive (see recent successful simulations for Hg (Steenbergen et al, 2017b)).…”

“…According to these calculations, the next nearest neighbor distance in the solid is R(5d) < R(6d) for the elements within the same group of the periodic table; hence, no evidence for strong relativistic effects are expected for this quantity in contrast to many other chemical properties (Iliaš and Pershina, 2017;Pershina, 2002;Türler and Pershina, 2013;Wang et al, 2016). Recently, using parallel tempering Monte-Carlo simulations within a many-body expansion for the atomic interaction potential (Smits et al, 2018), it was possible to confirm the melting temperature of T m = 202 K of 222 Rn originally measured in 1909 (Gray and Ramsay, 1909). Preliminary simulations suggest T m ≈ 320 K for Og (Smits et al, 2018).…”

Oganesson ist ein Halbleiter: Über die relativitische Bandlückenkontraktion in den schwersten Edelgasen

“…Allerdings lässt solch eine einfache Extrapolation außer Acht, dass die starke Verknüpfung von Atom‐ und Festkörpereigenschaften für die schweren Edelgase immer schwächer wird, da diese zunehmend polarisierbarer werden und somit stärker wechselwirken. Dieser Trend zeigt sich sehr deutlich im Verlauf der Kohäsionsenergie ( E coh , Bindungsenergie des Festkörpers pro Atom, rote Linie in Abbildung ), die bis Rn kontinuierlich auf 0.23 eV ansteigt und für Og plötzlich auf 0.45 eV springt . In dieser Hinsicht ist Og das reaktivste Edelgas, reaktiver sogar als das superschwere Copernicium (Cn, E coh =0.38 eV) in derselben Periode, und damit vermutlich auch ein Feststoff unter Normalbedingungen.…”

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

“…[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.…”