  We model within the kinetic Monte Carlo method the initiation of neck
formation and then later evolution of the resulting bridging regions for
configurations involving small particles initially positioned fitted between
large particles for situations typical for sintering of FCC nanocrystals, e.g.,
noble-metal nanoparticles. Neck initiation mechanisms by layering or clustering
are identified. The stability of the resulting bridging configurations depends
on several parameters, notably, on the relative small to large particle size
ratio, and we explain recent experimental findings on improved sintering
achieved for certain bimodal size distributions.
