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A combination of static light scattering and video microscopy is used to perform high precision measurements on the growth velocity of body centered cubic (bcc) crystals in a metastable colloidal melt of monodisperse, highly charged latex spheres. The crystals nucleate heterogeneously at the walls of a flat flow-through shear cell and solidification proceeds without significant disturbance by homogeneous nucleation. The suspension parameters packing fraction \ensuremath{\Phi} of the spheres and the concentration of screening electrolyte c are systematically varied for two kinds of particles with equal diameter but different charge. For all experimental conditions the growth velocities in the 〈110〉 direction collapse on a single curve if plotted against a reduced energy density difference ${\mathrm{\ensuremath{\Pi}}}^{\mathrm{*}}$ between the melt and the fluid at melting. Close to the phase boundary growth velocities vary linearly with increasing ${\mathrm{\ensuremath{\Pi}}}^{\mathrm{*}}$, and saturate at large ${\mathrm{\ensuremath{\Pi}}}^{\mathrm{*}}$ at a value of ${\mathit{v}}_{\mathrm{\ensuremath{\infty}}}$=9.1 \ensuremath{\mu}m ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$. The master curve can be fitted excellently by a Wilson-Frenkel growth law which was suggested to hold for the solidification of highly charged systems. A comparison of coefficients allows for the derivation of a quantitative estimation procedure for the difference in chemical potential \ensuremath{\Delta}\ensuremath{\mu} between melt and solid in terms of the thermal energy ${\mathit{k}}_{\mathit{B}}$T: \ensuremath{\Delta}\ensuremath{\mu}=${\mathrm{\ensuremath{\Pi}}}^{\mathrm{*}}$B. The best value for the conversion factor B is found to be B=(6.7\ifmmode\pm\else\textpm\fi{}0.1)${\mathit{k}}_{\mathit{B}}$T. In contrast to previous work on homogeneously nucleated crystals the growth velocity of the 〈110〉 face is limited by the reactionlike kinetics of registering preordered layers formed within an interface of finite thickness. We suggest a unified description covering also the growth of the rough interfaces of other crystal faces. (c) 1995 The American Physical Society

Using mode-coupling theory, we derive a constitutive equation for the nonlinear rheology of dense colloidal suspensions under arbitrary time-dependent homogeneous flow. Generalizing previous results for simple shear, this allows the full tensorial structure of the theory to be identified. Macroscopic deformation measures, such as the Cauchy-Green tensors, thereby emerge. So does a direct relation between the stress and the distorted microstructure, illuminating the interplay of slow structural relaxation and arbitrary imposed flow. We present flow curves for steady planar and uniaxial elongation and compare these to simple shear. The resulting non-linear Trouton ratios point to a tensorially nontrivial dynamic yield condition for colloidal glasses., Comment: accepted to Phys.Rev.Lett

The transition from a liquid to a glass in colloidal suspensions of particles interacting through a hard core plus an attractive square-well potential is studied within the mode-coupling-theory framework. When the width of the attractive potential is much shorter than the hard-core diameter, a reentrant behavior of the liquid-glass line, and a glass-glass-transition line are found in the temperature-density plane of the model. For small well-width values, the glass-glass-transition line terminates in a third order bifurcation point, i.e. in a A_3 (cusp) singularity. On increasing the square-well width, the glass-glass line disappears, giving rise to a fourth order A_4 (swallow-tail) singularity at a critical well width. Close to the A_3 and A_4 singularities the decay of the density correlators shows stretching of huge dynamical windows, in particular logarithmic time dependence., 19 pages, 12 figures, Phys. Rev. E, in print