The process of nanoparticle agglomeration as a function of the monomer-monomer interaction potential is simulated numerically by solving Langevin equations for a set of interacting monomers in three dimensions. The simulation results are used to investigate the structure of the generated clusters and the collision frequency between small clusters. Cluster restructuring is also observed and discussed. We identify a time-dependent fractal dimension whose evolution is linked to the kinetics of two cluster populations. The absence of screening in the Langevin equations is discussed and its effect on cluster translational and rotational properties is quantified.