Molecular dynamics study of a phase-separating fluid mixture under shear flow

Molecular dynamics simulation is carried out to study domain structures and rheological properties of a two-dimensional phase-separating binary fluid mixture under shear flow. In the early stage of the phase separation, anisotropic composition fluctuations appear immediately after the quench. As the domain grows, the anisotropy in the composition fluctuations increases. The quenched system eventually reaches a dynamical steady state, in which anisotropic domain structures are preserved. In the steady state, the shortest characteristic length scale R-perpendicular to of domains decreases with increasing shear rate (gamma) over dot as R-perpendicular to similar to (gamma) over dot (-1/3). Stringlike domain structures are observed in the strong shear regime, whereas randomly fluctuating patterns are observed in the weak shear regime. Moreover, the excess viscosity Delta eta is found to decrease with increasing shear rate as Delta eta similar to(gamma) over dot (-1/2) indicating that the phase-separating fluid mixtures an highly non-Newtonian because of domain deformations. [S1063-651X(99)10703-7].