Enhanced β relaxation induced by confinement in metallic glass film

It is widely appreciated that the β relaxation peak in loss modulus curve, upon an oscillatory excitation, is generally merged with α relaxation. The consensus on physical origin of β relaxation dynamics is still absent due to its subtle feature. Here we confine the metallic glass film between two substrates to enhance β relaxation using molecular dynamics simulations. Prominent humps occur at intermediate times in intermediate scattering function along confined direction, which features β relaxation. Layering phenomenon originating from confinement excludes the arbitrary hopping distance. Both particle collision with substrates and layering phenomenon increase β relaxation time window and delay α relaxation, facilitating observation of β relaxation.We provide an effective pathway to promote β relaxation and reveal the dominant mechanism from the atomic movement and structure characteristics.