Molecular dynamics simulation of homogeneous nucleation of KBr cluster

We perform molecular dynamics simulations to study the homogeneous nucleation in the freezing of molten potassium bromide clusters. The nucleation rates tend to decrease with increasing cluster size and temperature. The solid-liquid interfacial free energy σ_sl of 42.4-52.3 mJ/m² is close to the values predicted by Turnbull's relation and comparable to the experimental observation by Buckle and Ubbelohde. It is interesting to find that there is no cluster size effect on the critical nucleus size. Critical nucleus sizes inferred from classical nucleation theory are of 6.5-20.7 K⁺Br⁻ ionic pairs in the temperature range of 400-600 K. The critical nucleus size at bulk MD freezing temperature obtained by extrapolation is about 45 K⁺Br⁻ ionic pairs, which is comparable to the experimental value of NaCl.