title: Structure and short-time dynamics in suspensions of charged silica spheres in the entire fluid regime.
abstract: 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.
authors.affiliation: Faculty of Physics, A. Mickiewicz University, 61-614 Poznan, Poland.
authors.forename: J
authors.initials: J
authors.lastname: Gapinski
authors.forename: A
authors.initials: A
authors.lastname: Patkowski
authors.forename: A J
authors.initials: AJ
authors.lastname: Banchio
authors.forename: J
authors.initials: J
authors.lastname: Buitenhuis
authors.forename: P
authors.initials: P
authors.lastname: Holmqvist
authors.forename: M P
authors.initials: MP
authors.lastname: Lettinga
authors.forename: G
authors.initials: G
authors.lastname: Meier
authors.forename: G
authors.initials: G
authors.lastname: Nägele
mesh_terms: D004058:Diffusion; D004126:Dimethylformamide; D008956:Models, Chemical; D009994:Osmolar Concentration; D044367:Phase Transition; D012212:Rheology; D012822:Silicon Dioxide; D013057:Spectrum Analysis; D014965:X-Rays
chemical_list: D012822:Silicon Dioxide; D004126:Dimethylformamide