VISCOSITY OF A SIMPLE FLUID FROM ITS MAXIMAL LYAPUNOV EXPONENTS

We compute the viscosity of a fluid consisting of a large number of particles, N=108 and 864, as a function of shear rate from its maximum and minimum Lyapunov exponents. The calculation is based on an extension of Smales pairing rule of Lyapunov exponents for Hamiltonian systems to non-Hamiltonian systems in contact with a heat bath. The numerical values of these maximal Lyapunov exponents as a function of are determined using nonequilibrium molecular dynamics (NEMD) computer simulations. The computed this way agree with those obtained directly from NEMD within the experimental error of 2% for the triple-point N=108 system. A 1/2 dependence of for large is found up to a Péclet number of 5. © 1990 The American Physical Society.