Phase Transformation and Metallisation Studies of Some of the Alkali Iodides through High Pressure Electronic Structure Calculations

Self-consistent scalar relativistic band structure calculations for NaI, KI and RbI performed both in NaCl (B1) and CsCl (B2) structures using the tight-binding linear muffin tin orbital (TB-LMTO) method are reported. The valence bandwidths were calculated and compared with the available experimental and theoretical results. From the total energy calculations, the equilibrium lattice constants, the bulk moduli, the reduced volumes, and the corresponding pressures at which the compounds KI and RbI undergo B1 → B2 structural phase transitions as well as metallisation were calculated. These values agree reasonably well with the reported experimental values. The calculations rule out the possibility of B1 → B2 structural transformation in the case of NaI and the reason for this is discussed.