Abstract
It is found that the experimental absorption coefficient of β-FeSi2 in the range of photon energy of about 0.3 eV beyond the band gap is a few orders of magnitude larger than the first-principles calculated absorption coefficient. No critical points with negative hydrostatic pressure coefficients such as those of Si and GaAs are observed in β-FeSi2 near the band gap. The pressure coefficient for the direct band gap of β-FeSi2 is determined to be 15.9 meV/GPa. This small coefficient is due to the negative deformation potential of the valence-band maximum and the large bulk modulus of β-FeSi2.
