OPTICAL, X-RAY, AND BAND-STRUCTURE STUDIES OF IODINE AT PRESSURES OF SEVERAL MEGABARS

Optical reflectivity and x-ray-diffraction techniques have been used t o determine the electronic properties and structure of iodine to 181 a nd 276 GPa, respectively, in the diamond-anvil cell. X-ray measurement s were performed by energy dispersive diffraction with synchrotron rad iation. Monatomic metallic iodine transforms to an fcc structure at 53 GPa that remains stable to the maximum pressure. At 276 GPa, the volu me compression V/V0 is 0.324. Reflectivity data are consistent with a strong metallic character in iodine from 19 to 181 GPa. The linear muf fin-tin orbital method has been used to calculate the equation of stat e to 500 GPa and to model the reflectivity of iodine at high pressures .