Optical properties of isostructural β-FeSi2,OsSi2,Fe0.5Os0.5Si2 and Os0.5Fe0.5Si2

Abstract We have performed a comparative study of optical properties of isostructural β-FeSi2,OsSi2, and two ternary configurations of (FeOs)Si2 by first-principle calculations of band structure and the imaginary part of the dielectric function. The latter for β-FeSi2 and OsSi2 were compared to those deduced from ellipsometric measurements, indicating an excellent agreement. From theoretical calculations both binaries are found to be indirect gap semiconductors, whereas one ternary is characterised by a direct transition with high oscillator strength.