Abstract
Global structural searches performed for sodium amalgam compounds reveal six new and stable Na-Hg stoichiometries (e.g., NaHg3, NaHg4, Na2Hg, Na4Hg, Na5Hg and Na6Hg) under ambient and high-pressure conditions. With increasing Hg content in the compounds, the structure topology of Hg evolves from isolate atom (NamHgn, m/n >= 3, 0D), linear chains (Na2Hg, 1D), puckered honeycomb layers (Na3Hg2, 2D), diamond networks (NaHg, 3D), dodecahedron (NaHg2, 3D), to tetrakaidecahedron (NaHg3, 3D). Electronic structure analysis shows that Hg can attain higher negative oxidation states, transferring more than one electron from Na atoms to the Hg 6p orbitals. In NamHgn (m/n < 3) compounds, the covalent Hg-Hg interactions are found stemming from the sp hybridization. In Na4Hg, quasi-zero-dimensional (0-D) electride is found with the electrons located within the octahedrons of Na in the lattice. The present results establish the richness of sodium amalgam stoichiometries under ambient and high-pressure conditions.
NSTL
Elsevier