  We present results of computational modeling of the formation of uniform
spherical silver particles prepared by rapid mixing of ascorbic acid and
silver-amine complex solutions in the absence of a dispersing agent. Using an
accelerated integration scheme to speed up the calculation of particle size
distributions in the latter stages, we find that the recently reported
experimental results -- some of which are summarized here -- can be modeled
effectively by the two-stage formation mechanism used previously to model the
preparation of uniform gold spheres. We treat both the equilibrium
concentration of silver atoms and the surface tension of silver precursor
nanocrystals as free parameters, and find that the experimental reaction time
scale is fit by a narrow region of this two-parameter space. The kinetic
parameter required to quantitatively match the final particle size is found to
be very close to that used previously in modeling the formation of gold
particles, suggesting that similar kinetics governs the aggregation process and
providing evidence that the two-stage model of burst nucleation of
nanocrystalline precursors followed by their aggregation to form the final
colloids can be applied to systems both with and without dispersing agents. The
model also reproduced semiquantitatively the effects of solvent viscosity and
temperature on the particle preparation.
