Efficient viscosity estimation from molecular dynamics simulation via momentum impulse relaxation

A new momentum impulse relaxation method for obtaining the shear viscosity of Newtonian fluids using molecular dynamics simulations is introduced. The method involves the resolution of a decaying coarse-grain Gaussian velocit y profile in a properly thermostated simulation box. This localized velocit y profile, along with a modification of the periodic boundary conditions, a llows computations in a periodic box with minimal phonon feedback due to pe riodicity. The short-time decay of the small-amplitude velocity profile yie lds shear viscosities for atomic and molecular species that are in quantita tive agreement with those obtained using conventional techniques, but with more than an order of magnitude reduction in computational effort. (C) 2000 American Institute of Physics. [S0021- 9606(00)51130-1].