Title: Statistical thermodynamics of deformation in crystalline solids: A defect-rich perspective
Date and Time: 27th January 2023 (Friday) at 02:30 pm (Tea/Coffee: 02:15 pm)
Venue: Nevill Mott Hall, JNCASR
Title: Statistical thermodynamics of deformation in crystalline solids: A defect-rich perspective
Abstract: [pdf enclosed]
Crystalline solids have particles arranged in periodic structures. This long-range order is
associated with its resistance to deformation. However, crystals share their macroscopically
observed rigidity with other solids which do not have similar order in particle arrangements. This
simple observation illustrates the disconnect between micro-structural events governed by
statistical mechanics and observed macroscopic thermomechanical properties. Deformation in
crystals has consequences, and we present ways to address two fundamental questions in this
context. The impact of local-defects on the reversible mechanical response of complex crystals is
quantitatively connected to fluctuations at particle length scales[1, 2]. This is achieved by deriving
the laws of continuum mechanics starting from the classical many-body Hamiltonian and
circumventing simplifying assumptions regarding microscopic displacement fields. Next, we
explain[3] the shear-rate-dependent onset of plasticity in rigid solids in terms of an underlying
novel first-order phase transition between a uniformly stressed crystal and a stress-relaxed state.
This perspective implies that even an infinitesimal strain can render a crystalline solid metastable,
and the first passage time associated with the decay of the metastable state dictates the yield
point of the crystal at a given shear rate. This unique way of interpreting the yielding of ordered
solids relies on a general framework [4, 5] derived to systematically segregate affine and nonaffine
displacement fields at microscopic length scales.
[1]S. Ganguly, G. P. Shrivastav, S.-C. Lin, J. Häring, R. Haussmann, G. Kahl, M. Oettel and M. Fuchs, J. Chem.
Phys. 156, 064501 (2022).
[2]F. Miserez, S. Ganguly, R. Haussmann and M. Fuchs, Phys. Rev. E 106, 054125 (2022).
[3]P. Nath, S. Ganguly, J. Horbach, P. Sollich, S. Karmakar, S. Sengupta, PNAS115, E4322, (2018).
[4]S. Ganguly, S. Sengupta, P. Sollich, M. Rao, Phys. Rev. E, 87, 042801, (2013).
[5]S. Ganguly, S. Sengupta, P. Sollich, Soft Matter, 11, 4517, (2015).
