Elasticity of cerium up to 4.4 GPa by sound velocity measurements under hydrostatic pressure

Abstract

We report here the longitudinal and shear sound velocities on polycrystalline cerium under hydrostatic pressure across the iso-structural γ-α phase transition up to 4.4 GPa. Comparing with previous methods, the pressure-density relation of Ce has been calculated by integrating with the initial travel time and pressure without any fitting. The pressure correction of the Grüneisen parameter and linear expansion coefficient are taken into account during the integration process. The sound velocities, bulk modulus, shear modulus, Debye temperature, and vibrational entropy are achieved and have been compared with previous results. The bulk modulus of cerium in α phase agrees with the previous results determined by neutron and x-ray diffraction. The Debye temperature above and below the phase transition are and , respectively. The difference of the Debye temperature from respective experiment is found and has been expounded. We consider that the vibrational entropy change per atom of 0.44 kB as the Kondo collapse of 17% volume change, and 0.70 kB as the total change from γ phase to complete α phase.