Microscopic Theory of Onset of De-Caging and Bond Breaking Activated Dynamics in Ultra-Dense Fluids with Strong Short Range Attractions

Abstract

We theoretically study thermally activated elementary dynamical processes that precede full structural relaxation in ultra-dense particle liquids interacting via strong short range attractive forces. Our approach is based on a microscopic theory formulated at the particle trajectory level built on the dynamic free energy concept and an explicit treatment of how attractions control physical bonding. Mean time scales for bond breaking, the early stage of cage escape, and a fixed non-Fickian displacement are analyzed in the repulsive glass, bonded repulsive (attractive) glass, fluid, and dense gel regimes. The theory predicts a strong length-scale-dependent growth of these time scales with attractive force strength at fixed packing fraction, a much weaker slowing down with density at fixed attraction strength, and a strong decoupling of the shorter bond breaking time with the other two time scales that are controlled mainly by perturbed steric caging. All results are in good accord with simulations, and additional testable predictions are made. The classic statistical mechanical projection approximation of replacing all bare attractive and repulsive forces with a single effective force determined by pair structure incurs major errors for describing processes associated with thermally activated escape from transiently localized states.

arXiv comment6 pages, 4 figures

References in corpus (11)

• The Physics of the Colloidal Glass Transition
• Universal nature of particle displacements close to glass and jamming transitions
• Reentrant glass transition in a colloid-polymer mixture with depletion attractions
• Comparative simulation study of colloidal gels and glasses
• Elastically Cooperative Activated Barrier Hopping Theory of Relaxation in Viscous Fluids. I. General Formulation and Application to Hard Sphere Fluids
• Elastically Cooperative Activated Barrier Hopping Theory of Relaxation in Viscous Fluids. II. Thermal Liquids
• Unified Theory of Activated Relaxation in Liquids over 14 Decades in Time
• Evidence of a higher-order singularity in dense short-ranged attractive colloids
• Gelation as arrested phase separation in short-ranged attractive colloid-polymer mixtures
• Microscopic Theory for the Role of Attractive Forces in the Dynamics of Supercooled Liquids
• Microscopic Theory of the Influence of Strong Attractive Forces on the Activated Dynamics of Dense Glass and Gel Forming Fluids

Cited by in corpus (3)

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• Glassy behaviour of sticky spheres: What lies beyond experimental timescales?
• Microscopic Theory of the Elastic Shear Modulus and Length-Scale-Dependent Dynamic Re-Entrancy Phenomena in Very Dense Sticky Particle Fluids