Structural aspects of dense solid halogens under high pressure studied by x-ray diffraction—Molecular dissociation and metallization

Abstract

We have performed structural studies of solid bromine under ultrahigh pressures by using advanced synchrotron radiation X-ray diffraction techniques incorporated with a diamond-anvil high pressure cell. Reliable intensity measurements in its molecular phase up to 80 GPa, where it undergoes the molecular-to-monatomic phase transition (molecular dissociation), have enabled us to determine pressure dependence of molecular positions. By combining the previous results of iodine and chlorine, we have found an empirical scaling rule with respect to the crystal structure scaled with its intramolecular bond length for these three isostructural systems. By applying the Herzfeld criterion, we have also found a scaling rule for the metallization process prior to molecular dissociation.