Résumé
We present the results of molecular dynamics computer simulations of a binary
Lennard-Jones liquid confined between two parallel rough walls. These walls are
realized by frozen amorphous configurations of the same liquid and therefore
the structural properties of the confined fluid are identical to the ones of
the bulk system. Hence this setup allows us to study how the relaxation
dynamics is affected by the pure effect of confinement, i.e. if structural
changes are completely avoided. We find that the local relaxation dynamics is a
strong function of z, the distance of the particles from the wall, and that
close to the surface the typical relaxation times are orders of magnitude
larger than the ones in the bulk. Because of the cooperative nature of the
particle dynamics, the slow dynamics also affects the dynamics of the particles
for large values of z. Using various empirical laws, we are able to
parameterize accurately the z-dependence of the generalized incoherent
intermediate scattering function F_s(q,z,t) and also the spatial dependence of
structural relaxation times. These laws allow us to determine various dynamical
length scales and we find that their temperature dependence is compatible with
an Arrhenius law. Furthermore, we find that at low temperatures time and space
dependent correlation function fulfill a generalized factorization property
similar to the one predicted by mode-coupling theory for bulk systems. For thin
films and/or at sufficiently low temperatures, we find that the relaxation
dynamics is influenced by the two walls in a strongly non-linear way in that
the slowing down is much stronger than the one expected from the presence of
only one confining wall. ...