Paper Number
SC22 

Session
Suspensions, Colloids, and Granular Materials

Title
Shear-induced transition from disorder to coexisting ordered states in dense colloidal suspensions

Presentation Date and Time
October 12, 2021 (Tuesday) 2:20

Track / Room
Track 5 / Ballroom 6

Authors (Click on name to view author profile)

  1. Goyal, Abhay (National Institute of Standards and Technology, Infrastructure Materials Group)
    Goyal, Abhay (Georgetown University, Physics Department)
  2. Del Gado, Emanuela (Georgetown University)
  3. Jones, Scott (National Institute of Standards and Technology, Infrastructure Materials Group)
  4. Martys, Nicos (National Institute of Standards and Technology, Infrastructure Materials Group)

Author and Affiliation Lines (in printed abstract book)
Abhay Goyal1,2, Emanuela Del Gado2, Scott Jones1 and Nicos Martys1
1Infrastructure Materials Group, National Institute of Standards and Technology, Gaithersburg, MD 20878; 2Physics Department, Georgetown University, Washington, DC 20057

Speaker / Presenter 
Goyal, Abhay

Keywords
computational methods; colloids; suspensions

Text of Abstract
We report on simulations of a dense suspension of colloidal hard spheres under shear. Similar suspensions at rest have been shown to form a metastable glassy state or a stable crystal/liquid coexistance. We quench the system to an amorphous initial configuration and apply steady shear. At low rates, the system stays disordered over simulation times, but we find that at high rates, for Pe>1, the shear flow induces an ordering transition that drastically decreases the measured viscosity of the suspension. The ordering is analyzed in terms of the layering and the planar structure, and we determine that particles are packed into hexagonal crystal layers (with numerous defects) that slide past each other. By computing different order parameters, we find that the defects correspond to chains of particles in a square-like lattice. The hexagonal packing is more efficient and allows for higher local density, while the secondary lattice emerges in regions of lower local density. By computing the individual particle contributions to the stress tensor, we discover that the largest contributors to the shear stress are primarily located in these lower density regions.