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.