AMORPHIZATION AND MOLECULAR DISSOCIATION OF SNI4 AT HIGH PRESSURE

Synchrotron x-ray diffraction study establishes a novel structure sequence in ${\mathrm{SnI}}_{4}$ at high pressures to 153 GPa. A new crystalline phase responsible for the metallization is observed above 7.2 GPa. The pressure-amorphized ${\mathrm{SnI}}_{4}$ emerging above 15 GPa crystallizes at 61 GPa into another new structure having an apparent fcc lattice with a nearest-neighbor distance as short as 3.00 \AA{}. This provides evidence for the occurrence of molecular dissociation. Atomic arrangement in the nonmolecular phase and structural properties of the amorphous state are discussed.