Structure and Electronic Properties of Sodium at Multi-Hundred GPa Pressures

Xuchen Gong, PhD Qualifying Exam

Hopeman 224

At ambient conditions, sodium (Na) is an archetype of “nearly free electron” metals. Under compression, Na undergoes a series of phase transitions to low-symmetry structures, accompanied by a dramatic drop in the melting temperature. At 200 GPa, Na undergoes a conductor to insulator transition due to the valence electron localization at interstitial sites. There is no data beyond 200 GPa, and almost no data exist between 100-200 GPa. The proposed work will investigate the pressure-induced structural and electronic changes of Na at pressures approaching the TPa regime. The lattice and electronic structure of Na ramp-compressed at the OMEGA EP laser will be explored by x-ray diffraction and optical reflectance measurements respectively. Future work will improve the current diagnostics, adding temperature measurements and exploring other alkali metals.