Accurate, Large-Scale Density Functional Melting of Hg: Relativistic Effects Decrease Melting Temperature by 160 K

Abstract

Using first-principles calculations and the "interface pinning" method in large-scale density functional molecular dynamics simulations of bulk melting, we prove that mercury is a liquid at room temperature due to relativistic effects. The relativistic model gives a melting temperature of 241 K, in excellent agreement with the experimental temperature of 234 K. The nonrelativistic melting temperature is remarkably high at 402 K.

Copernicium: A Relativistic Noble Liquid

“…Extrapolating the liquid free energy to the intersection point with the gas phase affords a rough estimate for the boiling point of about 1000 K, similar to Zn with 1180 K and Cd with 1040 K, corresponding to a huge relativistic increase of 700 K. For Hg, calculations at the NR‐DFT/PBEsol level reported in Ref. afford a similar increase of the melting point from 241 K to 403 K. However, the nature of Hg as reflected in T m / E coh is only weakly affected, and it remains in the typical range for (Group 12) metals.…”

“…Its lifetime is sufficient to perform atom‐at‐a‐time experiments and explore periodic trends . Concerning these trends, its lighter congener Hg is known to exhibit some very unusual behavior compared to both Zn and Cd, with reported low melting and boiling points (Figure ), rendering Hg the only metallic liquid at room temperature and a superconductor with a transition temperature of 4.15 K . These periodic anomalies can be traced back to strong relativistic effects within this group, and, albeit to a far lesser extent, the lanthanide contraction originating from the poor nuclear shielding by the filled 4f shell .…”

“…As a result, and in contrast to all other members in this group, Cn may be regarded as a d‐block element, evident, for example, from the square‐planar structure of CnF 4 . Moreover, the relativistic valence s contraction in combination with the weak chemical bonding of the 6d 5/2 orbitals leads to an increasing chemical inertness of the Group 12 elements, which is reflected in the decrease of the cohesive energy E coh (see the green line in Figure ) …”

Colloquium : Superheavy elements: Oganesson and beyond

“…shown in the figure makes Cn chemically more inert compared to the lighter congener Hg (Eichler et al, 2008;Gaston et al, 2007;Pitzer, 1975;Steenbergen et al, 2017a), where relativistic effects are known to be large; they are responsible for Hg being the only elemental liquid metal at room temperature (Calvo et al, 2013;Steenbergen et al, 2017b).…”

“…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)).…”