NUMERICAL STUDY OF THE LOW-FREQUENCY ATOMIC DYNAMICS IN A LENNARD-JONES GLASS

We present a computer simulation study of a monatomic glass model. The investigated system consists of up to 32000 'argon' atoms, interactin g via a Lennard-Jones potential. Its dynamical properties have been in vestigated both by the time evolution of the atomic trajectories durin g molecular dynamics runs at low temperature and by the normal mode an alysis (NMA) in the inherent configuration. In the NMA, we used both t he direct diagonalization of the dynamical matrix and the spectral mom ent method. The vibrational density of states (DOS), the dynamic struc ture factors, the Raman spectrum and the spatial patterns of the eigen modes have been calculated. The Raman spectrum shows the characteristi c bump, that is the so-called 'boson peak', at frequencies where the D OS presents an excess of states with respect to the Debye behaviour. B y the analysis of the previous dynamical quantities and from the direc t inspection of the pattern of the eigenvectors, we derive a consisten t picture of the atomic dynamics in the boson peak energy region.