Evolution of neck radius and relaxation of coalescing nanoparticles

We use kinetic Monte Carlo simulations to investigate the coalescence of fcc nanoparticles via lattice-based diffusion of surface atoms. The radius of the neck region connecting the two nanoparticles is found to develop with characteristic power laws r∼t^a with a∼1/3 and a∼1/6 for the early and intermediate stages of coalescence, respectively. For late coalescence stages, when the nucleation of new atomic layers on nanoparticle facets is required for further coalescence, the nanoparticle size, temperature, and nanoparticle orientation all influence the development of the neck. In contrast, classical theory predicts an approximately constant value of a(∼1/6). We also examine the temperature dependence of the equilibration times for relaxing nanoparticles and distinguish the limiting processes to be nucleation of new germs on a facet and/or the detachment of atoms from atomic layers.