Energy Dissipation in Amorphous Solids during Elastic Deformation

Excitation of atomic vibrational modes is an important mechanism for energy dissipation in friction phenomena. In crystalline materials, the vibrational modes can be represented as plane waves, i.e. the phonons. This is in general not possible in amorphous solids due to structural disorder, which gives rise to different types of vibrational modes. Energy dissipation is related to the lifetime of these vibrational modes. Here we use large-scale molecular dynamics simulations to investigate energy dissipation mechanisms in a model amorphous solid and compare it to a crystalline solid. While the lifetimes of phonons show universal scaling ω^-2 in the limit of low frequencies ω, vibrational modes in the amorphous system show different scaling that depends on the type of the vibrational mode. We also carry out cyclic deformation of the amorphous solid in the elastic regime. In this limit, energy dissipation can be traced back to non-affine deformation. We demonstrate that the energy dissipation can be predicted by knowledge of the lifetimes and the non-affine displacement field.