The shear viscosity of Lennard-Jones fluids

Expressions for the shear viscosity have been obtained using its definition involving the time integral of the stress-stress correlation function and the memory function formalism. A secant hyperbolic and a Gaussian form of the memory function have been used. The parameters appearing in the memory function are determined from the first three nonvanishing frequency moments of the stress-stress correlation function. Expressions for the moments involving triplet and quadruplet correlation functions are calculated using the superposition and a low-order decoupling approximation respectively. These results have been used to calculate the shear viscosity of Lennard-Jones fluids over a wide range of densities and temperatures. The predicted results are found to be in good agreement with recent molecular dynamic data.