Lattice dynamics, phonons and mechanics in disordered and dissipative systems/Alessio Zaccone (University of Milan / University of Cambridge)

Where: Resnick building (#202), 2nd floor, seminar room

Abatract: A new atomistic calculation methodology has been recently
developed which extends lattice dynamics to disordered and "real" solids,
called Nonaffine Lattice Dynamics (NALD), based on the concept of nonaffine
displacements [1], which are ubiquitous in all real materials (crystals
with defects and grain boundaries, glasses etc) and are deeply connected to
local topology of the lattice in terms of the statistical degree of local
centrosymmetry [2,3]. This framework also allows one to predict the
dynamical mechanical response of "real" materials from the underlying
vibrational spectrum (VDOS) across the entire time-scale spectrum, thus
providing a possible solution for the well known problem of bridging time
and length scales in the dynamical simulation of materials at the atomic
level. The method has been shown to be predictive on the example of a model
glassy material of Kremer-Grest polymer chains [4], and recent results
extend the description at the atomistic level for real polymer glasses
(polyethylene, pDCPD, pNBOH, etc) [5]. I will also present recent results
aiming at rationalizing the effect of disorder and anharmonicity on phonons
in solids [6,7], with implications for superconductivity in amorphous
materials [8].

[1] A. Zaccone and E. Scossa-Romano, Phys. Rev. B 83, 184205 (2011).
[2] R. Milkus and A. Zaccone, Phys. Rev. B 93, 094204 (2016).
[3] B. Cui, A. Zaccone, D. Rodney, J. Chem. Phys. 151, 224509 (2019)
[4] V.V. Palyulin, C. Ness, R. Milkus, R. Elder, T. W. Sirk, and A.
Zaccone, Soft Matter 14, 8475-8482 (2018).
[5] R. M. Elder, A. Zaccone, T. W. Sirk, ACS Macro Letters 8, 1160 (2019).
[6] M. Baggioli and A. Zaccone, Phys. Rev. Lett. 122, 145501 (2019).
[7] M. Baggioli and A. Zaccone, arXiv:1911.03351 (2019).
[8] M. Baggioli, C. Setty, A. Zaccone, arXiv:2001.00404 (2020).