DISSIPATIVE PARTICLE DYNAMICS - BRIDGING THE GAP BETWEEN ATOMISTIC AND MESOSCOPIC SIMULATION

We critically review dissipative particle dynamics (DPD) as a mesoscop ic simulation method. We have established useful parameter ranges for simulations, and have made a link between these parameters and chi-par ameters in Flory-Huggins-type models. This is possible because the equ ation of state of the DPD fluid is essentially quadratic in density. T his link opens the way to do large scale simulations, effectively desc ribing millions of atoms, by firstly performing simulations of molecul ar fragments retaining all atomistic details to derive chi-parameters, then secondly using these results as input to a DPD simulation to stu dy the formation of micelles, networks, mesophases and so forth, As an example application, we have calculated the interfacial tension sigma between homopolymer melts as a function of chi and N and have found a universal scaling collapse when sigma/rho k(B)T chi(0.4) is plotted a gainst chi N for N>1. We also discuss the use of DPD to simulate the d ynamics of mesoscopic systems, and indicate a possible problem with th e timescale separation between particle diffusion and momentum diffusi on (viscosity). (C) 1997 American Institute of Physics.