Experimental and theoretical study of metallic iodine

Insulating molecular iodine is known to transform gradually to a metallic state between 4 and 17 GPa of pressure at room temperature. An anomaly found in early shock-compression experiments has been taken to indicate that actual dissociation of the iodine molecules does not occur until much higher pressures. We report new experimental and theoretical results for the shock-compression curve that show no evidence for this anomaly. Furthermore, our calculations for an assumed monatomic, metallic phase are in agreement with the new shock data, and suggest that the ${\mathrm{I}}_2$ bond may be destroyed in the vicinity of the metallic transition.