Title: Localized excitations in glasses: an application to elastic wave attenuation

Speaker: Geert Kapteijns (UvA)

Abstract:

A glass is a solid in which the atoms vibrate around certain well defined but random equilibrium positions, as opposed to a crystal in which the atoms are situated in a lattice. The disordered nature of a glass gives it certain distinctive properties that the same material in crystalline form does not have — for example, a crystalline silica window pane (besides being prohibitively expensive to manufacture), does not insulate against the cold nearly as well as the common pane made of silica glass. Furthermore, a glass is by definition out of thermodynamic equilibrium (being metastable to the crystalline ground state), so that its behavior may be highly sensitive to its preparation protocol, and slowly evolve over time.

In the group of Edan Lerner, we try to explain the rich behavior of glasses by reference to a population of localized defects that arise from glasses’ self-organized disordered microscopic structure, which we study by computer simulation. In this talk, I will give a brief introduction to this line of inquiry, and then highlight a recent application to the physics of wave attenuation / heat conduction in glasses. I show that the population of defects determines the spatial distribution of the elastic constants, which in turn sets the wave attenuation rate / phonon mean free path, thereby validating a continuum elastic theory due to Schirmacher for the thermal conductivity and specific heat of glasses.

Reference: https://aip.scitation.org/doi/full/10.1063/5.0038710

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