Invariance of experimental observables with respect to coarse-graining in standard and many-body dissipative particle dynamics

TL;DR

This paper investigates how coarse-graining affects experimental observables in dissipative particle dynamics, deriving a temperature dependence and scaling laws to ensure invariance across different levels of coarse-graining, and extends these findings to many-body DPD.

Contribution

It derives a scaling method to make system properties invariant under coarse-graining in standard and many-body DPD simulations, clarifying temperature dependence and demonstrating practical applicability.

Findings

System properties can be made invariant with respect to coarse-graining.

The method accurately predicts surface tensions of binary solvent mixtures.

Many-body DPD effectively simulates complex fluids across coarse-graining levels.

Abstract

Dissipative particle dynamics (DPD) is a well-established mesoscale simulation method. However, there have been long-standing ambiguities regarding the dependence of its (purely repulsive) force field parameter on temperature as well as the variation of the resulting experimental observables, such as diffusivity or surface tension, with coarse-graining (CG) degree. Here, we revisit the role of the CG degree and rederive the temperature dependence in standard DPD simulations. Consequently, we derive a scaling of the input variables that renders the system properties invariant with respect to CG degree, and illustrate the versatility of the method by computing the surface tensions of binary solvent mixtures. We then extend this procedure to many-body dissipative particle dynamics (MDPD) and, by computing surface tensions of the same mixtures at a range of CG degrees, demonstrate that this newer method, which has not been widely applied so far, is also capable of simulating complex fluids of practical interest.