This article reviews our recent x-ray studies on solid halogens under high pressure. We found an empirical scaling rule including atomic coordinates for iodine and bromine. By applying the Herzfeld criterion, we also found a scaling rule for the metallization process prior to molecular dissociation. The Maximum Entropy Method was employed to analyze the powder diffraction data and obtain the electron density map in solid iodine at pressures up to 20 GPa. The electron density between adjacent iodine molecules is shown to form a two-dimensional network around 16 GPa in association with metallization.
