The interplay between the structural relaxation and the rheological response
of a binary LJ glass former is studied via MD simulations. In the quiescent
state, the model is well known for its sluggish dynamics and a two step
relaxation of correlation functions at low temperatures. An ideal glass
transition temperature of Tc=0.435 has been identified in the previous
studies via the analysis of the system's dynamics in the frame work of the mode
coupling theory of the glass transition [W. Kob and H.C. Andersen, PRE 51, 4626
(1995)]. Here, we test wether a signature of this ideal glass transition can
also be found under shear. Indeed, the following distinction in the structural
relaxation is found: In the supercooled state, the structural relaxation is
dominated by the shear at relatively high shear rates, γ˙, whereas
at sufficiently low γ˙ the (shear-independent) equilibrium
relaxation is recovered. In contrast to this, the structural relaxation of a
\emph{glass} is always driven by shear. This distinct behavior of the
correlation functions is also reflected in the rheological response. In the
supercooled state, the shear viscosity, η, decreases with increasing shear
rate (shear thinning) at high shear rates, but then converges toward a constant
as the γ˙ is decreased below a (temperature-dependent) threshold
value. Below Tc, on the other hand, the shear viscosity grows as η∝1/γ˙ suggesting a divergence at γ˙=0. Thus,
within the accessible observation time window, a transition toward a
non-ergodic state seems to occur in the driven glass as the driving force
approaches zero.Comment: 12 pages, 9 figure