The high pressure behavior of the structural and electronic properties of KC1 is studied
with use of the density functional pseudopotential method within local-density
approximation. Atzero pressure, the rocksalt phase is found to be lower in energy than CsCl
structure. However, we predict a phase transition into CsCI structure at a pressure of about
1.5 GPa. The calculated ground state properties such as lattice constant, bulk modulus, and
its pressure derivative are in reasonable agreement with experiment. The electronic band
structure at normal and high pressures is also calculated. It is found that metallization occurs
for rocksalt and CsCI structures at ultrahigh pressures