Lattice dynamics of Eu from nuclear inelastic scattering and first-principles calculations

We report on combined determination of the density of phonon states of an epitaxial Eu metallic single crystal by in situ ¹⁵¹Eu nuclear inelastic scattering and by first-principles phonon calculations. Thermodynamic (specific heat and vibrational entropy) and elastic (mean atomic displacement, mean force constant, and sound velocity) properties of Eu were obtained. The very good agreement between the experiment and theory indicates that in general, the lattice dynamics of the $4f$ metals can be reliably investigated by the ab initio approach applying the direct method.