  We present a study of the dynamics and structural changes for
trans-1,2-dichloroethylene between high and low density liquids using neutron
scattering techniques (diffraction, small angle neutron scattering and time of
flight spectroscopy) and molecular dynamics simulations. We show that changes
in the short range ordering of molecules goes along with a change of the
molecular dynamics: both structure and dynamics of the high density liquid are
more cooperative than those of the low density liquid. The microscopic
mechanism underlying the cooperative motions in the high density liquid has
been found to be related to the backscattering of molecules due to a strong
correlation of molecular ordering.
