Structure and short-time dynamics in suspensions of charged silica spheres in the entire fluid regime

J. GAPINSKI; A. PATKOWSKI; ADOLFO J. BANCHIO; J. BUITENHUIS; P. HOLMQVIST; M. P. LETTINGA; G. MEIER; G. NÄGELE

JOURNAL OF CHEMICAL PHYSICS

AMER INST PHYSICS

Año: 2009 vol. 130 p. 84503 - 84503

0021-9606

We present an experimental study of short-time diffusion properties in fluidlike suspensions ofmonodisperse charge-stabilized silica spheres suspended in dimethylformamide. The static structurefactor S(q), the short-time diffusion function D(q), and the hydrodynamic function H(q)have beenprobed by combining x-ray photon correlation spectroscopy experiments with static small-anglex-ray scattering. Our experiments cover the full liquid-state part of the phase diagram, includingde-ionized systems right at the liquid-solid phase boundary. We show that the dynamic data can beconsistently described by the renormalized density fluctuation expansion theory of Beenakker andMazur over a wide range of concentrations and ionic strengths. In accordance with this theory andStokesian dynamics computer simulations, the measured short-time properties cross overmonotonically, with increasing salt content, from the bounding values of salt-free suspensions tothose of neutral hard spheres. Moreover, we discuss an upper bound for the hydrodynamic functionpeak height of fluid systems based on the Hansen–Verlet freezing criterion. © 2009 AmericanInstitute of Physics. [DOI: 10.1063/1.3078408]