Abstract:
We used dynamic light scattering (DLS) and computer simulations based on the fluctuating lattice Boltzmann
equation (LBE) method to study the short-time Brownian dynamics of colloidal particles that interact like hard
spheres. The dynamics are characterized by a wave-vector-dependent 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., crystallization at f=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 equation method for the fluid phase coupled to
Newtonian mechanics for the colloidal particles. For all samples studied, close quantitative agreement is found
between the results of the DLS experiments and the LBE simulations.