Low-frequency acoustic phonons in nanometric CeO2 particles

Low-dimensional vibrational modes are calculated using elastic continuum approximation for CeO2 nanoparticles, which considers the nanoparticle as an elastic sphere, embedded in an infinite, homogeneous and isotropic elastic medium and found to decrease with particle size. However, to incorporate the effect of matrix, the anisotropic and finite medium is taken into account. The presence of medium significantly affects the Raman peaks representing acoustic modes and results into the line width broadening accompanied by damping of modes, which are explained on the basis of mismatch of acoustic parameters of matrix and nanoparticles. The mechanical coupling plays a key role in the damping mechanism of Raman frequencies.