Examining different NEMD methods in simulating nanoscale fluid at high shear rates

Abstract

In this paper, the non-Newtonian behaviour of a simple fluid is simulated via three different non-equilibrium molecular dynamics (NEMD) algorithms: boundary-driven shear; homogeneous shear; and reverse-NEMD (RNEMD). The pros and cons of each approach are discussed and results are compared. It is found that the accessible shear rate is very limited when using boundary-driven shear and RNEMD, whereas homogeneous shear is capable of imposing a substantially higher shear rate. However, the boundary-driven shear reproduces rheological experiment setups and the RNEMD yields much better statistically calculated properties. The material functions, velocity profiles, and microstructures of the fluid are examined and the formations of fluid structures are elucidated. The homogeneous shear is shown to be the most appropriate NEMD method to simulate fluids under strong shear, with the smallest number of limitations.