An exact measurement of nucleation incubation times in isothermal crystallizations of liquid metal Al via configuration heredity

Nucleation induction time τ^∗ is a crucial parameter in the classical nucleation theory, which is intimately associated with the steady-state nucleation rate I₀ in the homogenous nucleation. To examine the impact of temperatures T on τ^∗(T) in the isothermal crystallizations of liquid metal Al, a series of molecular dynamics simulations are performed at different undercoolings ΔT_m. With the help of cluster type index method based on Honeycutt–Anderson bond-type index, a cluster analysis method based on the continuous heredity of crystal clusters is developed to further distinguish nuclei from various embryos. By means of the transient heredity of crystal clusters, a nucleation incubation time τ_c different from nucleation induction time, i.e., a sum of incubation time of embryo τ_e and its effective growth time τ_g^eff prior to arriving the critical size, is introduced and exactly measured. For the critical nuclei emerged in the transient nucleation stage, the τ_c are found to be long compared with the steady-state nucleation stage and mainly depend on an effective growth of incubated embryos, while those in steady-state nucleation stage are mostly decided by a successful incubation of initial embryos. Also, relative to the τ^∗(T) derived from I₀(T) at different ΔT_m, these measured τ_c(T) are very small, but their average times τ¯_c(T) in the whole region are mirror symmetric to I₀(T).