Velocity shearing and scaling RNEMD: a minimally perturbing method for simulating temperature and momentum gradients

Abstract

We present a new method for introducing stable non-equilibrium velocity and temperature gradients in molecular dynamics simulations of heterogeneous and interfacial systems. This method conserves both the linear momentum and total energy of the system and improves previous reverse non-equilibrium molecular dynamics (RNEMD) methods while retaining equilibrium thermal velocity distributions in each region of the system. The new method avoids the thermal anisotropy produced by previous methods by using isotropic velocity scaling and shearing (VSS) on all of the molecules in specific regions. To test the method, we have computed the thermal conductivity and shear viscosity of model liquid systems as well as the interfacial friction coefficients of a series of solid–liquid interfaces. The method's ability to combine the thermal and momentum gradients allows us to obtain shear viscosity data for a range of temperatures from a single trajectory.