Pressure-induced amorphization of CuFeS2 studied by Fe-57 nuclear resonant inelastic scattering

Static and dynamic structural properties of CuFeS2 under high pressure were investigated by x-ray diffraction and Fe-57 nuclear resonant inelastic scattering. Using x-ray diffraction, we obtained evidence that a pressure-induced amorphization occurs at about 6.3 GPa, which represents a metal-insulator transition. Although partial phonon densities of states extracted from Fe-57 nuclear resonant inelastic scattering spectra are similar in the two phases, the derived thermodynamical parameters show anomaly at the transition. The results of extracted partial phonon densities of states and ab initio phonon calculations indicate that this pressure-induced amorphization is caused by anomalous pressure dependences of the lower optical phonon branches and the initial slopes of the transverse acoustic phonon branches.