Structure and short-time dynamics in suspensions of charged silica spheres in the entire fluid regime.
We present an experimental study of short-time diffusion properties in fluidlike suspensions of monodisperse charge-stabilized silica spheres suspended in dimethylformamide. The static structure factor S(q), the short-time diffusion function D(q), and the hydrodynamic function H(q) have been probed by combining x-ray photon correlation spectroscopy experiments with static small-angle x-ray scattering. Our experiments cover the full liquid-state part of the phase diagram, including de-ionized systems right at the liquid-solid phase boundary. We show that the dynamic data can be consistently described by the renormalized density fluctuation expansion theory of Beenakker and Mazur over a wide range of concentrations and ionic strengths. In accordance with this theory and Stokesian dynamics computer simulations, the measured short-time properties cross over monotonically, with increasing salt content, from the bounding values of salt-free suspensions to those of neutral hard spheres. Moreover, we discuss an upper bound for the hydrodynamic function peak height of fluid systems based on the Hansen-Verlet freezing criterion.
Gapinski
J
J
Faculty of Physics, A. Mickiewicz University, 61-614 Poznan, Poland.
Patkowski
A
A
Banchio
A J
AJ
Buitenhuis
J
J
Holmqvist
P
P
Lettinga
M P
MP
Meier
G
G
Nägele
G
G
D004058:Diffusion; D004126:Dimethylformamide; D008956:Models, Chemical; D009994:Osmolar Concentration; D044367:Phase Transition; D012212:Rheology; D012822:Silicon Dioxide; D013057:Spectrum Analysis; D014965:X-Rays
D012822:Silicon Dioxide; D004126:Dimethylformamide