Sound Velocity of FeNiSi alloy by Inelastic X-ray Scattering

Abstract

Inelastic x-ray scattering measurements at high pressure have been performed on the BL35XU beamline at SPring-8. We have measured the spectra of pure iron and the Fe_0.83Ni_0.09Si_0.08 alloy in diamond anvil cell from 50 GPa to 135 GPa at room temperature. Spectra were collected in the transmission geometry with the X-ray beam impinging on the sample through the diamonds along the compression axis of the pressure cell. Based on the spectra of the inelastic scattering, we calculated the sound velocity of the sample at high pressure. The sound velocity and the density of the alloy follow a linear relation, i.e., the Birch's law. The Vp-density (d) relation for Fe_0.83Ni_0.09Si_0.08 alloy can be expressed as Vp (m/sec) = 1.50(±0.17)d(kg/m2) - 6570(±1690) of which slope is steeper than that of pure iron.