Kinetic heterogeneities and non-linear rheology of highly supercooled liquids

Abstract

Supercooled liquids with soft-core potentials are studied via molecular dynamics simulations in two and three dimensions in quiescent and sheared conditions. We demonstrate that bond breakage events among particle pairs occur collectively in clusters. The average life time, τ b ( γ ̇ ) , of bonds tends to the α relaxation time, τ α, for weak shear, γ ̇ ≪1/τ α , and decreases as 1/ γ ̇ for strong shear, γ ̇ ≫1/τ α . The structure factor, S b( q), of the broken bonds may be fitted to the Ornstein–Zernike form. The correlation length, ξ, is uniquely expressed in terms of τ b ( γ ̇ ) as ξ∼τ b ( γ ̇ ) 1/4 in two dimensions and ξ∼τ b ( γ ̇ ) 1/2 in three dimensions for any T and γ ̇ in glassy states. The viscosity is of order τ b ( γ ̇ ) for any γ ̇ , so the shear stress tends to a limiting stress for γ ̇ τ α ≫1 .