Nonclassical nucleation kinetics in the crystallization of a supercooled melt

VV Pisarev, RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A, 88, 1382-1387 (2014).

DOI: 10.1134/S0036024414080226

A molecular dynamics simulation of homogenous nucleation of a crystal in supercooled aluminum melt is performed. Nucleation rates at a temperature of 900 K in the range of pressures from 12 to 15 GPa are calculated. Analysis of the mean first-passage times of crystalline cluster sizes is performed. A stepwise dependence of the mean first- passage time on crystal nucleus size is observed, in contrast to the sigmoidal dependence that follows from classical nucleation theory. Based on the data from atomistic simulations, it is established that the form of the free energy barrier during nucleation differs significantly from the one assumed in classical nucleation theory for a spherically symmetric nucleus. It is supposed that the observed differences are apparently due to the complex structure of the crystalline nucleus.

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