As colloidal particles interact at length scales much shorter than their size, short-range penetrable pair potentials are often used to model the effective inter-particle interactions. Stochastic hard collision (SHC) dynamics was developed as an alternative to the class of penetrable coarse-grained potentials. SHC dynamics includes the effects of inter-penetrability of soft particles while retaining the computational efficiency of hard collision dynamics. We extended the original SHC algorithm to model an important class of soft colloids: hard-core soft-shell (HCSS) colloids. Using molecular dynamics and Monte-Carlo simulations, we examined the behavior of this complex soft system on varying the occupied volume fraction and the shell-softness. The shell-softness is observed to profoundly and non-trivially affect the thermodynamic and dynamic behavior of the HCSS system. Even at the same effective volume fraction, shell-softness strongly affects the behavior of the system. Furthermore, we uncovered the structural origin of this non-trivial effect of shell-softness (the effect that truly depends on the softness of the system not on the reduced volume fraction due to inter-particle penetration) on the system. While this model colloidal system is useful on its own to characterize the phase behavior of soft colloids, we anticipate that it may also set a stage for the efficient simulation of complex fluids.

Modeling soft colloids using stochastic hard collision dynamics

256th National Meeting (2018)

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