Shear viscosity in a moderately dense hard sphere gas

The three contributions to the shear viscosity in a moderately dense gas—namely, the kinetic, the cross, and the potential part—are calculated separately and the intimate interrelationship between those coefficients and the corresponding correlation functions is shown. The starting point is the calculation of the relevant correlation functions within the ’’successive uncorrelated binary collision’’ model. We prove that while the cross-correlation is strictly proportional to the kinetic correlation function, we obtain two contributions for the potential part of the correlation function one proportional to the kinetic part and the second proportional to a delta function, due to the instantaneous transfer of momentum in hard sphere collisions.