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 Tm 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 < Tm ) 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.