Heterogeneous Nucleation Mechanisms in Systems with Large Lattice Misfit Demonstrated by the Pb(l)/Cu(s) System
H Men and ZY Fan, METALS, 12, 1583 (2022).
Our current understanding of heterogeneous nucleation has been largely confined to the classical nucleation theory (CNT) that was postulated over 100 years ago based on a thermodynamic approach. Further advances in heterogeneous nucleation research requires detailed knowledge of atomistic activities at the liquid/substrate interface. In this work, using a classical molecular dynamics (MD) simulation, we investigated the atomistic mechanisms of heterogeneous nucleation in systems with a large lattice misfit (|f| > 12.5%) demonstrated by the liquid Pb and solid Cu system (denoted as the Pb(l)/Cu(s) system) with a misfit of 27.3%. We found that heterogeneous nucleation in systems with a large misfit takes place in two distinctive steps: (1) Prenucleation creates a coincidence site lattice (CSL) on the substrate surface to accommodate the majority (f(csl)) of the initial misfit (f) and (2) Heterogeneous nucleation accommodates the residual misfit f(r) (f(r) = misfit - f(csl)) at the nucleation temperature to create a plane of the new solid phase (a two-dimensional (2D) nucleus) through either a three-layer dislocation mechanism if f(r) < 0 or a three-layer vacancy mechanism if f(r) > 0, such as in the case of the Pb(l)/Cu(s) system.
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