From Molecular Dynamics to hydrodynamics - a novel Galilean invariant thermostat

摘要

This article proposes a novel thermostat applicable to any particle-baseddynamic simulation. Each pair of particles is thermostated either (withprobability P) with a pairwise Lowe-Andersen thermostat, or (with probability1-P) with a thermostat that is introduced here, which is based on a pairwiseinteraction similar to the Nose-Hoover thermostat. When the pairwiseNose-Hoover thermostat dominates (low P), the liquid has a high diffusioncoefficient and low viscosity, but when the Lowe-Andersen thermostat dominates,the diffusion coefficient is low and viscosity is high. This novelNose-Hoover-Lowe-Andersen thermostat is Galilean invariant and preserves bothtotal linear and angular momentum of the system, due to the fact that thethermostatic forces between each pair of the particles are pairwise additiveand central. We show by simulation that this thermostat also preserveshydrodynamics. For the (non-interacting) ideal gas at P=0, the diffusioncoefficient diverges and viscosity is zero, while for P>0 it has a finitevalue. By adjusting probability P, the Schmidt number can be varied by ordersof magnitude. The temperature deviation from the required value is at least anorder of magnitude smaller than in Dissipative Particle Dynamics (DPD), whilethe equilibrium properties of the system are very well reproduced. Applicationsof this thermostat include all standard molecular dynamic simulations of denseliquids and solids with any type of force field, as well as hydrodynamicsimulation of multi-phase systems with largely different bulk viscosities,including surface viscosity, and of dilute gases and plasmas.