Lattice Dynamics and Structural Phase Transitions in Eu2O3.

Using the density functional theory, we study the structural and lattice dynamical properties of europium sesquioxide ($Eu_{2}O_{3}$) in the cubic, trigonal, and monoclinic phases. The obtained lattice parameters and energies of the Raman modes show a good agreement with the available experimental data. The Eu-partial phonon density of states calculated for the cubic structure is compared with the nuclear inelastic scattering data obtained from a 20 nm thick $Eu_{2}O_{3}$ film deposited on a YSZ substrate. A small shift of the experimental spectrum to higher energies results from a compressive strain induced by the substrate. On the basis of lattice and phonon properties, we analyze the mechanisms of structural transitions between different phases of $Eu_{2}O_{3}$.