The density of vibrational states in amorphous materials is known to present an unusual shape related as “boson peak”, and responsible for the very specific thermal behaviour of these systems. In this letter, we show how the vibrational modes of a model Lennard-Jones glass are affected by a mechanical load. Far from a mechanical instability, vibrational modes can be described at low frequency by weak scattering of acoustic modes. Close to a plastic instability, some of them localize. We show how the shape of the “localized” vibrational modes, juste before the plastic instability, is directly related to the spatial organization of the plastic rearrangements. A measurement of the spatial organization of the low-frequency vibrational modes could thus be used as a predictor for plastic activity
