Pressure-induced electron topological transitions in Ba-doped Si clathrate

Ba8Si46 is the archetype of the Si clathrates family. X-ray diffractions have revealed an unusual homothetic isostructural transition at ∼14–16 GPa. Raman experiments, however, suggested even more transitions at lower pressure. We present evidence showing that successive electronic topological transitions are responsible for the transformations. It is shown that the electronic structure of Ba8Si46 is easily perturbed by the environment. Reverse Monte Carlo calculations and in-situ resistivity measurements revealed continual changes in the structure and electrical properties upon compression. This finding is corroborated by results of x-ray Raman scattering study in the vicinity of the Ba N4,5 and Si L2,3 absorption edges.