Phonon Spectroscopy of Oriented hcp Iron

High-pressure phonon spectroscopy was performed on iron in the bcc and hcp phase up to 40 GPa using the nuclear inelastic scattering (NIS) of synchrotron radiation (SR). In hcp iron we observe differences in the density of phonon states for spectra measured with different orientations of the diamond anvil cell (DAC) with respect to the SR beam. These differences are attributed to a preferred orientation of the hexagonal c -axis along the load axis of the DAC. These texture effects are used, in conjunction with theoretical calculations, to extract density of phonon states as seen parallel and perpendicular to the c -axis of hcp iron.