Molecular Dynamics Simulations of Nucleation Process from Supercooled Liquid Pt with EAM Potentials

Abstract

The homogeneous nucleation process induced by supercooling liquid Pt has been studied by means of molecular dynamics employing the embedded-atom method for the potential energy. The process was simulated by cooling an equilibrated liquid to a low temperature, while structure analysis was performed during the subsequent time evolution of the system under constant temperature and pressure conditions. In order to investigate the effects of degree of supercooling and cooling rate on crystallization, cooling temperature was varied from 900 to 1300 K and three processes at different cooling rates were studied. The results proved that certain degree of supercooling is necessary for homogeneous nucleation of crystals due to the existence of a free energy barrier in forming critical nuclei from supercooled liquid, as described by the classical theory of homogeneous nucleation. The scale of the degree of supercooling has much effect on the incubation period of homogeneous nucleation and nucleation rate. The crystallization towards fcc and hcp phases takes place in all homogeneous nucleation processes from liquid in our simulations. The progression of crystallization is sensitive to cooling rate. A very high cooling rate has been found to prolong incubation period, decrease nucleation rate, thus suppress crystallization. This may be associated with the phenomenon that high cooling rate prohibits the rearrangement of atoms towards forming a crystal lattice at high temperatures during the early stage of cooling.