Fig. 1: Stability, structure, and chemical bonding of Ca2AuB6.
From: Ambient-pressure superconductivity in covalent Au-B frameworks stabilized by electropositive metals
a Convex hull of predicted Ca-Au-B compounds relative to stable elemental solids and binary compounds at 50 GPa. Fm-3m Au, Pm-3m Ca, and γ-B28 were selected as reference elemental structure. The colored circles represent phases that may be thermodynamically stable, metastable or unstable, and the color bar denotes the magnitude of the relative formation enthalpies (ΔH) of the compounds. The AlB2-type AuB255 with a positive formation enthalpy is also plotted. b Phonon dispersion curve of Ca2AuB6 at ambient pressure. c Free energy as a function of MD time at the temperature of 2800 K for Ca2AuB6 at ambient pressure, and the inset illustrates the trajectories of the atoms within Ca2AuB6 within the 2 × 2 × 2 supercell after MD equilibration. d Predicted crystal structure of P4/mmm Ca2AuB6. The blue and golden spheres represent Ca and Au atoms, while the two inequivalent B atoms are denoted by green (B1) and magenta (B2) spheres, respectively. e Calculated ELF of Ca2AuB6 in the (001) plane. f Calculated charge density of Ca sublattice in Ca2AuB6, with an isosurface value of 0.008 e/bohr3.
