SHORT-TIME BROWNIAN-MOTION IN COLLOIDAL SUSPENSIONS - EXPERIMENT AND SIMULATION

We used dynamic light scattering (DLS) and computer simulations based on the fluctuating lattice Boltzmann equation (LEE) method to study th e short-time Brownian dynamics of colloidal particles that interact li ke hard spheres. The dynamics are characterized by a e-vector-dependen t diffusion coefficient D-S(Q). Using DLS, we have mesaured D-S(Q) in the vicinity of the main (first) peak in the structure factor see, for samples of poly-methylmethacrylate particles at volume fractions phi ranging from dilute up to the disorder-order transition (i.e., crystal lization at phi=0.494). In addition we have determined the short-time self-diffusion (D-S(S)) and collective-diffusion D-S(C) coefficients. We have extracted the same quantities from simulations of equilibrium configurations of hard spheres using a fluctuating lattice Boltzmann e quation method for the fluid phase coupled to Newtonian mechanics for the colloidal particles. For all samples studied, close quantitative a greement is found between the results of the DLS experiments and the L EE simulations.