The Role of Three-Body Interactions on the Equilibrium and Non-Equilibrium Properties of Fluids from Molecular Simulation

摘要

The aim of this work is to use molecular simulation to investigate the role ofudthree-body interatomic potentials in noble gas systems for two distinctudphenomena: phase equilibria and shear flow. In particular we studied theudvapour-liquid coexisting phase for pure systems (argon, krypton and x enon) andudfor an argon-krypton mixture, utilizing the technique called Monte Carlo Gibbsudensemble. We also studied the dependence of the shear viscosity, pressure andudenergy with the strain rate in planar Couette flow, using a non-equilibriumudmolecular simulation (NEMD) technique.udThe results we present in this work demonstrate that three-body interactionsudplay an important role in the overall interatomic interactions of noble gases. Thisudis demonstrated by the good agreement between our simulation results and theudexperimental data for both equilibrium and non-equilibrium systems.udThe good results for vapour-liquid coexisting phases encourage performingudfurther computer simulations with realistic potentials. This may improve theudprediction of quantities like critical temperature and density, in particular ofudsubstances for which these properties are difficult to obtain from experiment.udWe have demonstrated that use of accurate two- and three-body potentials forudshearing liquid argon and xenon displays significant departure from theudexpected strain rate dependencies of the pressure, energy and shear viscosity.udFor the first time, the pressure is convincingly observed to vary linearly with anudapparent analytic g&2 dependence, in contrast to the predicted g&3/ 2 dependenceudof mode -coupling theory. Our best extrapolation of the zero -shear viscosity forudargon gives excellent agreement (within 1%) with the known experimental data.udTo the best of our knowledge, this the first time that such accuracy has beenudachieved with NEMD simulations. This encourages performing simulations withudaccurate potentials for transport properties.