Electronic structure of Mg2Si by combining electron diffraction and first-principles calculations

We have used accurate convergent beam electron diffraction to determine the structure factors of the reflections most sensitive to the valence-electron distribution in Mg2Si. The experimental values agree well with calculations of the structure factors based on density functional theory. Based on the experimentally scrutinized electron structure calculations we show that this promising thermoelectric material is highly ionic, arriving at the charge Mg21.45+Si2.9-.