Shear-induced melting and reentrant positional ordering in a system of spherical particles

Abstract

Computer simulations of dense systems of soft spheres subjected to a shear flow show not only the phenomena of shear-induced melting—transition from a crytalline to an amorphous state—but, at high shear rates, a second nonequilibrium phase transition to a new positionally ordered state. The particles form strings parallel to the stream lines; the strings, in turn, are arranged in a hexagonal pattern. Simulation data on the rheological properties, non-Newtonian viscosity, shear dilatancy, and stress growth and values for the shear moduli are presented; some theoretical ideas for the explanation of these phenomena are discussed.