Excess of low frequency vibrational modes and glass transition: a molecular dynamics study in Lennard-Jones systems at constant pressure
H.M. Flores-Ruiz , G.G. Naumis

Instituto de Fisica, UNAM, Mexico D.F., Mexico

Abstract: Using molecular dynamics at constant pressure, the relationship between the excess of low frequency vibrational modes (known as the boson peak) and glass transition is investigated for Lennard-Jones systems. It is observed that the quadratic mean displacement is enhanced by such modes, as predicted using a harmonic Hamiltonian for metastable states. As a result, glasses loose mechanical stability at lower temperatures than the corresponding crystal, since the Lindemann criterion is observed. Finally, we found that the average force and elastic constant is reduced in the glass due to such excess of modes. The ratio between average elastic constants can be approximated using the 2/3 rule between melting and glass transition temperature.