Dynamic equivalence between atomic and colloidal liquids

TL;DR

This paper demonstrates a dynamic equivalence between atomic and colloidal liquids, showing that their long-time diffusion behaviors are fundamentally similar when scaled appropriately, supported by simulation comparisons.

Contribution

It establishes a theoretical and simulation-based link between atomic and colloidal liquid dynamics, extending the known colloidal freezing criterion to atomic systems.

Findings

Long-time diffusion properties are equivalent when scaled by D_S.

The ratio D_L/D_S is the same for atomic and colloidal systems with identical interactions.

Simulations confirm the dynamic universality class for model systems.

Abstract

We show that the kinetic-theoretical self-diffusion coefficient of an atomic fluid plays the same role as the short-time self-diffusion coefficient D_S in a colloidal liquid, in the sense that the dynamic properties of the former, at times much longer than the mean free time, and properly scaled with D_S, will indistinguishable from those of a colloidal liquid with the same interaction potential. One important consequence of such dynamic equivalence is that the ratio D_L/ D_S of the long-time to the short-time self-diffusion coefficients must then be the same for both, an atomic and a colloidal system characterized by the same inter-particle interactions. This naturally extends to atomic fluids a well-known dynamic criterion for freezing of colloidal liquids[Phys. Rev. Lett. 70, 1557 (1993)]. We corroborate these predictions by comparing molecular and Brownian dynamics simulations on (soft- and hard-sphere) model systems, representative of what we may refer to as the "hard-sphere" dynamic universality class.