Identification of flow mechanisms for a soft crystal

We study the behavior under flow of soft, spherical micelles forming a fee phase at high volume fraction. Due to the size (300 Angstrom) of the elementary objects, the structure can be investigated through Xrays and neutron scattering, at rest and under flow in a Couette cell. Using scattering in two perpendicular directions, different mechanisms of flow are identified. At intermediate shear (around 100 s(-1)) the system exhibits the so called layer sliding mechanism where two dimensional hexagonal compact planes of spheres align themselves with the Couette cell walls. At lower shear rate, the fee structure is locally preserved, and the flow is mediated by defects between crystallites. At high shear rate, we observe the melting of the structure and a liquid-like structure factor. Moreover, we were able to use the existence of the layer sliding regime to generate a fee monocrystal by annealing the satcking faults between the decorrelated planes created by the layer sliding.