Dissipative particle dynamics: Dissipative forces from atomistic simulation

We present a novel approach of mapping dissipative particle dynamics (DPD) into classical molecular dynamics. By introducing the invariant volume element representing the swarm of atoms we show that the interactions between the emerging Brownian quasiparticles arise naturally from its geometric definition and include both conservative repulsion and dissipative drag forces. The quasiparticles, which are composed of atomistic host solvent rather than being simply immersed in it, provide a link between the atomistic and DPD levels and a practical route to extract the DPD parameters as direct statistical averages over the atomistic host system. The method thus provides the molecular foundations for the mesoscopic DPD. It is illustrated on the example of simple monatomic supercritical fluid demonstrating good agreement in thermodynamic and transport properties calculated for the atomistic system and DPD using the obtained parameters.