Dynamic structure factor of a dilute Lennard-Jones gas

We calculate the leading correction term in the density expansion of the dynamic structure factor for a Lennard-Jones fluid using the Boltzmann equation. The qualitative behavior is found to be very similar to the hard-sphere result reported by Kamgar-Parsi et al. [Phys. Rev. A 35, 4781 (1987)]. A comparison was made with the results from the neutron scattering experiment by Verkerk et al. [Phys. Rev. Lett. 67, 1262 (1991)] for dilute argon gases. Several possibilities to explain the discrepancies of the present results from the experiment are proposed.