Finite-size effects in the phonon density of states of nanostructured germanium: A comparative study of nanoparticles, nanocrystals, nanoglasses, and bulk phases

Finite-size effects in the phonon density of states (PDOS) of nanostructured materials (nanoparticles, nanocrystals, embedded nanoparticles, and nanoglasses) are systematically studied by means of molecular dynamics simulations, where germanium was used as representative reference material. By comparing with the PDOS of single crystalline and amorphous structures, the physical origins of additional or vanishing vibrational modes or frequency shifts were identified. Our findings are discussed in terms of phonon confinement effects, structural disorder, and surface stresses and provide a general view on the interplay of nanostructural features and lattice vibrations