We describe a method for obtaining the intermediate scattering function $I(Q,t)\mathrm{}$ from a computer simulation: it is an extension of our earlier calculation [Salacuse, Denton, and Egelstaff, Phys. Rev. E 53, 2382 (1996)] for the $\overrightarrow{t}0$ limit. We use this approach to obtain $I(Q,t)\mathrm{}$ for low Q and t from molecular dynamics (MD) simulations of a model krypton fluid whose atoms interact via a truncated Aziz pair potential, and the results are compared over their range of validity to $I(Q,t)\mathrm{}$ determined by the standard MD method and also by a time expansion approach. In its range of validity our approach is much more efficient than the standard MD method; however, it covers a restricted range of t due to the movement of density fluctuations (sound waves) through the simulated fluid which produces an anomaly in the time behavior of $I(Q,t).$ By analyzing $I(Q=0,t)\mathrm{}$ the velocity of sound in the simulation is determined, and the results compare favorably with published experimental results for the sound velocity of liquid krypton.

• Received 25 May 2000

DOI:https://doi.org/10.1103/PhysRevE.64.051201