Crossover between equilibrium and shear-controlled dynamics in sheared liquids

We present a numerical simulation study of a simple monatomic LennardJones liquid under shear flow, as a function of both temperature T and shear rate ˙γ. By investigating different observables we find that i) It exists a line, Tγ˙ , in the (T- ˙γ) plane that sharply marks the boarder between an “equilibrium” and a “shear-controlled” region for both the dynamic and the thermodynamic quantities; and ii) Along this line the structural relaxation time, τα(Tγ˙), is proportional to ˙γ −1 , i. e. to the typical time-scale introduced by the shear flow. Above Tγ˙ the liquid dynamics is unaffected by the shear flow, while below Tγ˙ both T and ˙γ control the particle motion.