PHASE-TRANSFORMATION AND METALLIZATION STUDIES OF SOME OF THE ALKALI IODIDES THROUGH HIGH-PRESSURE ELECTRONIC-STRUCTURE CALCULATIONS

Self-consistent scalar relativistic band structure calculations for Na I, KI and RbI performed both in NaCl (B1) and CsCl (B2) structures usi ng the tight-binding linear muffin tin orbital (TB-LMTO) method are re ported. The valence bandwidths were calculated and compared with the a vailable experimental and theoretical results. From the total energy c alculations, the equilibrium lattice constants, the bulk moduli, the r educed 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 possi bility of B1 --> B2 structural transformation in the case of NaI and t he reason for this is discussed.