Excess of low frequency vibrational modes, glass transition and inherent structures

Using a repulsive soft potential, molecular dynamics (MD) at constant pressure in a monodispersive glass and MD in a binary glass at constant volume, we are able to study the relationship between the excess of low frequency vibrational modes (known as the boson peak), square mean displacement (SMD) and glass transition temperature Tg. It is observed that the SMD is enhanced by such modes as predicted using a harmonic Hamiltonian for metastable states. As a result, glasses lose mechanical stability at lower temperatures than the corresponding crystal. We found that the average force is reduced in the glass due to such excess of modes. For the binary binary glass, we are able to study the SMD in the inherent structures (IE) over several temperatures below and around Tg. In this way, we can make the statistics of SMD over diferent IE.