Electronic structure of β-Fe(Si 2− xGe x) ternaries

Abstract

The geometrical and electronic structures of β-Fe(Si 2− x Ge x ) ternaries were investigated using first principles pseudopotential calculations based on generalized gradient approximation density function theory. These compounds are indirect-bandgap semiconductors with theoretical energy band gaps ranging from 0.51 to 0.79 eV . Substitution of Ge for Si in β-FeSi 2 leads to a reduction of the gap width and an increase in the volume of the unit cell with almost the same shape of the last valence band and the first conduction band but for the Y point. The analyses of bond overlap population and Mulliken population revealed that the covalency between Fe and Si atoms are strengthened by increasing Ge content and that the electron transfer occurs from Ge to Fe or Si.