Predicting the stability and electronic structure of alkali metal aurides

Density functional theory calculations of phonon modes predict that some compounds of the alkali metal aurides family, general formula A2MAu6 (A = K+, Rb+ or Cs+; M = Ti, Zr, Hf, Sn or Pb), have stable three-dimensional phase with a double perovskite-type structure and cubic Fm3m space group (K2PtCl6-type). Bader’s charge analysis shows that most electron density is located within the six atoms at the octahedra vertices like double perovskite halides. However, the short spacing between Au anions enables d-orbital interactions between them. Compounds of this family, with group 4 metals only, carry conduction states around the Gamma point (k = 0). On the other hand, compounds with group 14 metals possess more conduction states around all the Brillouin zone and have electron pockets in their bandstructure. These compounds provide further insights into the unusual anionic behavior of gold and present other alternatives for the construction of divergent nanodevices.