Density- and Temperature-Dependent Potentials: Redefinition of the Local Density to Improve the Simulation of Liquids...

In this work, we apply the mesoscopic Generalized Energy-Conserving Dissipative Particle Dynamics (GenDPDE) method (J. Bonet Avalos et al., Phys. Chem. Chem. Phys. 2019, 21, 24891) to analyze liquid phases. We demonstrate that the traditional DPD estimator of the particle local density is inadequate for the simulation of liquid phase conditions, as it leads to an unphysical behavior, typically in the form of particle clustering, that modifies the local structure and prevents the system from equilibrating at the sought thermodynamic state point. We therefore propose an alternative definition for the local density calculation which significantly improves its estimation and crucially allows us to recover physically meaningful results. We prove the beneficial effects of this redefinition by analyzing the thermodynamic properties and local structure of liquid argon and water, drawing a comparison between the outcome of equilibrium simulations considering the two density estimators. With the introduction of the new local density expression, GenDPDE is suitable for the qualitative and quantitative analysis of complex fluid systems in a variety of relevant scenarios, including liquid phases.