Systematics of thes→dandp→delectronic transition at high pressure for the elements I through La

Static and shock-wave compression measurements as well as theoretical calculations show that I, Xe, Cs, Ba, and La exhibit similar behavior at high pressure determined by the transfer of electrons from $6s$- or $5p$-like states to nearby $5d$ conduction bands. In shock-wave experiments these transitions occur thermally, while in static experiments, they occur by transfer to degenerate states. Such transitions profoundly influence the high-pressure thermodynamic properties of these materials, as will be reviewed in this paper.