Incomplete molecular chaos within dense-fluid shock waves.

Large-scale molecular dynamics simulations of an M(s) = 4.3 shock in dense argon (rho = 532 kg m(3), T = 300 K) and an M(s) = 3.6 shock in dense nitrogen (rho = 371 kg m(3), T = 300 K) have been performed. The two-point molecular velocity correlation function is calculated within slices in plane with the shock wave. Long-range (approximately ten molecular radii) positive correlations (correlation coefficient 0.05) are observed for the shock-normal velocity component, the in-plane velocity component, and the rotation rates. No correlations are found upstream or downstream of the shock, indicating that this is a nonequilibrium effect. These correlations violate one of the assumptions underlying the Boltzmann equation.