Metallization of liquid iodine

The metallization of melted iodine observed above the temperature of 900 K and pressure of 3 GPa (V.V. Brazhkin et al., High Press. Res. 6 (1992) 363) has been interpreted using a percolation model of overlapping electron shells (classically accessible spheres) of virtual atoms in molecules. The percolation threshold density falls in the middle of normal densities of the melt and solid. At high temperatures, the pressure near the transition point has a thermal nature mainly caused by seven partially free valence electrons of virtual atoms. Due to a very steep potential within the outer 5s25p5 shell of iodine, the transition yields a sharp increase of the conductivity even at rather high temperatures. With a model of virtual atoms, we have calculated the permittivity, energy gap, and conductivity in the electron–hole and percolation channels which are compared with experimental data.