Influence of Disorder on the Bad Metal Behavior in Polar Amalgams.

The two new ternary amalgams K 1- x Rb x Hg 11 [ x = 0.472(7)] and Cs 3- x Ca x Hg 20 [ x = 0.20(3)] represent two different examples of how to create ternary compounds from binaries by statistical atom substitution. K 1- x Rb x Hg 11 is a Vegard-type mixed crystal of the isostructural binaries KHg 11 and RbHg 11 [cubic, BaHg 11 structure type, space group Pm 3̅ m , a = 9.69143(3) Å, Rietveld refinement], whereas Cs 3- x Ca x Hg 20 is a substitution variant of the Rb 3 Hg 20 structure type [cubic, space group Pm 3̅ n , a = 10.89553(14) Å, Rietveld refinement] for which a fully substituted isostructural binary Ca phase is unknown. In K 1- x Rb x Hg 11 , the valence electron concentration (VEC) is not changed by the substitution, whereas in Cs 3- x Ca x Hg 20 , the VEC increases with the Ca content. Amalgams of electropositive metals form polar metal bonds and show "bad metal" properties. By thermal analysis, magnetic susceptibility and resistivity measurements, and density functional theory calculations of the electronic structures, we investigate the effect of the structural disorder introduced by creating mixed-atom occupation on the physical properties of the two new polar amalgam systems.