Size dependence of the melting temperature and mechanisms of the coalescence/sintering on the nanoscale

We have proposed to use the nanoparticle (NP) melting temperature T_m to distinguish between the coalescence and sintering processes on the nanoscale. According to our molecular dynamics results, obtained on Au NPs, the coalescence of nanoproplets may be interpreted as a hydrodynamic phenomenon on the nanoscale, and the characteristic coalescence time τ is a linear function of the initial particle radius r ₀. In turn, the sintering of two crystalline NPs (T < T_m) relates to a grain boundary formation as a result of an alignment of the crystallographic orientations of the sintering NPs, and in this case a dependence of τ on r ₀ has not been revealed. (paper)