Acoustic velocities and elastic properties of pyrite (FeS₂) to 9.6 GPa

Ultrasonic interferometry was utilized in conjunction with synchrotron-based X-ray diffraction and X-radiographic imaging to determine the compressional and shear wave velocities and unit-cell volumes of pyrite (FeS₂) at room temperature and pressures up to 9.6 GPa. Fitting all of the experimental volume and velocity data to third-order finite-strain equations yielded the adiabatic zero-pressure bulk and shear moduli and their first pressure derivatives: K_S0=138.9(7) GPa, G₀=112.3(3) GPa, (∂K_S0/∂P)_T=K_S0′=6.0(1), (∂G₀/∂P)_T=G₀′=3.0(<1), where the numbers in parentheses represent the 1σ uncertainty in the last significant digit. These results are in good agreement with several previous static compression studies on this material but differ quite strongly from the results obtained via first principles calculations. This study presents the first direct measurement of the bulk shear properties of this material.