Static compression of ε-FeSi

X-ray diffraction patterns of ε-FeSi have been measured at pressures up to ∼53 GPa with good signal-to-noise ratio and high resolution by using synchrotron radiation. In order to refine the crystal structure, a Rietveld analysis has been performed. The structure of ε-FeSi is cubic with space group P2₁3 and a = 4.4781 ± 0.0026 Å. A third-order Birch-Murnaghan equation of state fit to the experimental data yields V ₀ = 89.80 ± 0.15 ų, with a B₀ of 204.7 ± 4.9 GPa and B₀ = 5.6 ± 0.3. The bulk modulus obtained from this study is not only in very good agreement with those of some previous experimental studies but also in good agreement with those obtained from first-principles calculations.