Phase stability and electronic structure of k-ag intermetallics at high pressure

The very unusual structural features observed in the recently characterized high pressure novel K-Ag alloys can be rationalized using simple electron counting rules and a moment analysis of the electronic density of states. The stability of the alloys is attributed to almost complete electron transfer from K 4s bands to Ag 5s bands and spatially extended Ag 5p bands. This allows for efficient Ag-Ag bonding interactions at an unusually long distance of 5.54 Å and exceptionally short K-K bonds due to reduced repulsive interactions between the K⁺ ions. The general principles developed here are applicable to the understanding of the structure and bonding of other high pressure intermetallic alloys.