Frustration of structural fluctuations upon equilibration of shear melts

Abstract We report on the formation of amorphous solids from aquaeous suspensions of charged colloidal spheres. Comprehensive light scattering and microscopic studies show that in these systems the nucleation rate density continuously increases to very high values. At the highest particle densities of 47.5 μm −3 (packing fraction Φ =0.146) an amorphous state is observed of only short range order, finite static shear modulus and frozen long time dynamics. This state is composed of a piling of––as we propose pre-critical––nuclei. Differences from the Hard Sphere case are discussed in some detail. There the arrest of density fluctuations is observed and described by Mode Coupling scenarios. In the charged system a pronounced pre-ordering of the metastable melt is present which leads to structural fluctuations i.e. the formation of bond orientational order with more or less retained density. In both scenarios, however, mutual frustration of fluctuations, which evolve during the equilibration of the metastable (shear-) melt, is the main source of vitrification.