Dresden 2017 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 61: Topical session: Dynamics, relaxation and deformation in deeply supercooled metallic liquids and glasses V - dynamical response

MM 61.1: Topical Talk

Donnerstag, 23. März 2017, 11:45–12:15, IFW A

Towards a dissipative atomic-scale theory of the dynamical response of metallic glasses — •Alessio Zaccone — University of Cambridge, U.K.

One of the most fruitful concepts to characterize the deformation of metallic glasses has been that of nonaffine displacements [1]-[3], defined as additional atomic motions on top of the affine displacements prescribed by the macroscopic strain tensor. Using this, and recognizing that nonaffine displacements ultimately originate from the breaking of local centrosymmetry on every atom in the amorphous lattice [4], opens up the possibility of formulating a "nonaffine lattice dynamics" of metallic glasses. I will show that new viscoelastic sum-rules can be derived from a system-bath Hamiltonian of the Zwanzig-Caldeira-Leggett type which leads to a low-temperature Generalized Langevin Equation for dissipative nonaffine motions. This approach can be combined with a mode-coupling result [5] for the atomic-scale damping coefficient (a non-Markovian friction which accounts for memory-effects) to give predictions of dynamic response in agreement with experimental results of mechanical spectroscopy. The approach also provides a robust connection with the vibrational density of states. Finally, a possible route to explain the beta-relaxation process with this approach is outlined.

[1] A. Zaccone & E. Scossa-Romano, Phys. Rev. B (2011). [2] T.C. Hufnagel, C.A. Schuh, M.L. Falk, Acta Mater. (2016). [3] S. V. Ketov, Y.H. Sun, et al., Nature (2015). [4] R. Milkus and A. Zaccone, Phys. Rev. B (2016). [5] L. Sjoegren and A. Sjoelander, J. Phys. C: Solid State Phys. (1979).