Structure Determination of Simple Metals at Unprecedented Compressions

Na exhibits a variety of low-symmetry phases with complex structures above 100 GPa, and is reported to become an optically transparent insulator with fully localized valence electrons in the hP4 phase above 200 GPa. However, results from our recent ramp compression investigations do not agree with previous results, showing an additional diffraction peak. We firstly aim to resolve this discrepancy. One can furthermore determine the degree of electron localization from the intensity of the (002) peak. We will measure this intensity for the first time, providing the first direct evidence for the electride state in Na. Our result will also show whether Na behaves differently under dynamic compression than it does under static conditions.