Low frequency vibrational modes and thermal relaxation in glasses
G.G. Naumis [1], F. Salazar [1], R. Romero-Arias [2]

[1] Instituto de Fisica, UNAM, Mexico D.F., Mexico

Abstract: We present a non-linear model that allows us to explore the relationship between energy relaxation, thermal conductivity and the excess of low frequency vibrational modes (LFVM) that are present in glasses. The model is a chain of the Fermi-Pasta-Ulam type, with non-linear second neighbor springs added at random. We show that the time for relaxation is increased as LFVM are removed, while the thermal conductivity diminishes. These results are important in order to understand the role of the cooling speed and thermal conductivity during a glass transition. Also, the model provides evidence for the fundamental importance of LFVM in the Fermi-Pasta-Ulam problem.