Experimental charge densities of semiconducting cage structures containing alkaline earth guest atoms

That guest atoms donate electrons to framework atoms is a generally accepted concept. Nevertheless, evidence for the presence of neutral guest atoms in thermoelectric clathrate structures is presented in the form of experimental X-ray charge density analysis and X-ray absorption near-edge structure (XANES) data. The picture shows the deformation density (DD) determined by the maximum entropy method for Ba₈Ga₁₆Ge₃₀; the DD shows that both the Ba guest atoms are disordered.