Ab initio study revealing a layered structure in hydrogen-rich KH6 under high pressure

By adding small amounts of potassium to hydrogen, the energetically preferred compound KH6 forms above 70 GPa and metalizes within 166 GPa. Two-layered C2/m and C2/c structures of KH6 discovered here contain H-2 and H-3 units under high pressure. The metallic C2/c phase is found to be a one-dimensional conductor with a conducting hydrogen-bonded network and an insulating potassium chain. The layered hydrogen-dominant compound KH6 is found to be a good example of pressure-induced metallization, which originates from a hydrogen sublattice at lower pressures than those in pure hydrogen system due to the chemical precompression from heavier element potassium.