Electronic band structure and metallization of KI and RbI under high pressure

The metallization and the phase transition of the simple alkali iodides potassium iodide (KI) and rubidium iodide (RbI) are investigated through their band structures. Under high pressure KI and RbI undergo a first order structural phase transition from the NaCl structure (B1) to the CsCl structure (B2). The band structure, density of states (DOS), electronic charge distribution and total energy are computed as a function of volume for both B1 and B2 phases. The values of pressure under reduced volume are calculated using Birch-Murnaghan's equation of state. Our results of the metallization pressure in KI and RbI are compared with that of CsI. It is found, that the charge transfer from s and p states to the d state will cause metallization and the metallization pressure increases with a decrease of the atomic radii. Also alkali iodides with a NaCl structure at normal pressure have a greater metallization pressure than those having CsCl structure at normal pressure.