How are sound waves attenuated when they travel in a medium? How to damp most efficiently the vibrations due to an earthquake? Inversely, how to build a stable resonator? or avoid loosing energy when a laser beam rebounds on a mirror in a gravitational wave detector, the process which currently limits the precision of these very large interferometers. In order to answer these questions, we need to understand how mechanical energy is dissipated in materials. This process is complex and originates from distinct sources depending on the frequency of the deformation and the ratio between its wavelength and the characteristic length scales of the medium. The situation is particularly complex in disordered solids, which show a hierarchy of length scales. In this talk, we will discuss energy dissipation in oxide glasses and in particular silica, which is both a model glass and a technological glass used in many applications, including MEMS and optical coatings. We will show how atomistic modeling can address both the very low (~ MHz) and very high (~ THz) frequency regimes, using different approaches. At low frequencies, dissipation is controlled by the thermally activated relaxation of local bi-stable regions, two-level systems, whose properties can be measured by sampling the potential energy landscape of the glass. By way of contrast, at high frequencies, the glass dynamics becomes harmonic and can be described using a normal mode analysis. We will see that in silica, which forms a tetrahedral network without coordination defects, dissipation and viscoelastic effects at both low and high frequencies are due to the vibration and reorientation of the Si-O-Si bonds between tetrahedra.
Biography:
David Rodney graduated from Ecole Paris Mines and University of Orsay. After a PhD at the Polytechnic Institute of Grenoble, he became a lecturer at SIMaP lab at INP Grenoble. From 2008 to 2009 he was a visiting professor at MIT in the department of "Material Science and Engineering". IUF junior in 2009, he joined the UCB Lyon 1 and ILM in teams Model ization of Condensed Matter and Interfacesand SOPRANO. Currently David works on the simulation of the mechanical properties of solids.
Add to Calendar
2019-06-05T15:00:002019-06-05T16:30:00CM Seminar: From MEMS to Gravitational Wave Detectors: modeling energy dissipation in oxyde glasses at the atomic scaleEvent Information:
Abstract:
How are sound waves attenuated when they travel in a medium? How to damp most efficiently the vibrations due to an earthquake? Inversely, how to build a stable resonator? or avoid loosing energy when a laser beam rebounds on a mirror in a gravitational wave detector, the process which currently limits the precision of these very large interferometers. In order to answer these questions, we need to understand how mechanical energy is dissipated in materials. This process is complex and originates from distinct sources depending on the frequency of the deformation and the ratio between its wavelength and the characteristic length scales of the medium. The situation is particularly complex in disordered solids, which show a hierarchy of length scales. In this talk, we will discuss energy dissipation in oxide glasses and in particular silica, which is both a model glass and a technological glass used in many applications, including MEMS and optical coatings. We will show how atomistic modeling can address both the very low (~ MHz) and very high (~ THz) frequency regimes, using different approaches. At low frequencies, dissipation is controlled by the thermally activated relaxation of local bi-stable regions, two-level systems, whose properties can be measured by sampling the potential energy landscape of the glass. By way of contrast, at high frequencies, the glass dynamics becomes harmonic and can be described using a normal mode analysis. We will see that in silica, which forms a tetrahedral network without coordination defects, dissipation and viscoelastic effects at both low and high frequencies are due to the vibration and reorientation of the Si-O-Si bonds between tetrahedra.
Biography:
David Rodney graduated from Ecole Paris Mines and University of Orsay. After a PhD at the Polytechnic Institute of Grenoble, he became a lecturer at SIMaP lab at INP Grenoble. From 2008 to 2009 he was a visiting professor at MIT in the department of "Material Science and Engineering". IUF junior in 2009, he joined the UCB Lyon 1 and ILM in teams Model ization of Condensed Matter and Interfaces and SOPRANO. Currently David works on the simulation of the mechanical properties of solids.
Event Location:
BRIM 311
Abstract: