L.D. Robinson, K.S.N. Vikrant, J.E. Blendell, C.A. Handwerker, and R.E. García “Interfacial and Volumetric Melting Regimes of Sn Nanoparticles.” Acta Materialia. In Press. 2022. https://doi.org/10.1016/j.actamat.2022.118084

Abstract

A thermodynamically consistent phase field formulation was developed to describe what has been historically known as the premelted surface layer in Sn nanoparticles. Two interfacial phases were identified: 1) a disordered interfacial phase, i.e., the experimentally observed premelted surface layer; and 2) an ordered surficial phase displaying a remnant degree of order in fully melted particles. A volumetric partially disordered particle core is predicted to exist for small particle sizes, r<7 nm. Four regimes of behavior are discussed: a) the classic premelting regime, for r>20 nm, in which the surface of the particle forms a liquid shell at temperatures below melting with clear delineation between the solid core and the premelted surficial liquid shell, as traditionally expected; b) the transition regime, for 5<r<20 nm, in which the volumetric chemical potential and interfacial forces balance each other out; c) the disordered volume phase regime, for r<5 nm, in which a disordered interphase dominates the thermodynamic equilibrium of the system resulting in a partially crystalline core, and d) the mesoscale regime, in which the nanoparticles are no longer considered crystalline and experience an associated decrease in latent heat.