Velocity autocorrelation function in supercooled liquids: Long time tails and anomalous shear wave propagation.
Molecular dynamic simulations are performed to reveal the long time behavior of the velocity autocorrelation function (VAF) by utilizing the finite size effect in a Lennard Jones binary mixture. Whereas in normal liquids the classical positive t^ 3/2} long time tail is observed, we find in supercooled liquids a negative tail. It is strongly influenced by the transfer of the transverse current wave across the period boundary. The t^ 5/2} decay of the negative long time tail is confirmed in the spectrum of VAF. Modeling the long time transverse current within a generalized Maxwell model, we reproduce the negative long time tail of the VAF, but with a slower algebraic t^ 2} decay.
Physical review. E