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Molecular Dynamics Simulation of Surface Nucleation during Growth of an Alkane Crystal.

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Title: Molecular Dynamics Simulation of Surface Nucleation during Growth of an Alkane Crystal.
Authors: Bourque, Alexander1, Locker, C. Rebecca2, Rutledge, Gregory C.1 rutledge@mit.edu
Source: Macromolecules. 5/10/2016, Vol. 49 Issue 9, p3619-3629. 11p.
Subjects: Molecular dynamics, Crystal growth, Polyethylene, Nucleation, Alkanes, Temperature effect
Abstract: Crystal growth from the melt of n-pentacontane (C50) was studied by molecular dynamics simulation. Quenching below the melting temperature gives rise to propagation of the crystal growth front into the C50 melt from a crystalline polyethylene surface. By tracking the location of the crystal-melt interface, crystal growth rates between 0.02 and 0.05 m/s were observed, for quench depths of 10-70 K below the melting point. These growth rates compare favorably with those from a previous study by Waheed et al. [Polymer 2005, 46, 8689-8702]. Next, surface nucleation was identified with the formation of two-dimensional clusters of crystalline sites within layers parallel to the propagating growth front. Critical nucleus sizes, waiting times, and rates for surface nucleation were estimated by a mean first passage time analysis. A surface nucleation rate of ~0.05 nm-2 ns-1 was observed, and it was nearly temperature-independent. Postcritical "spreading" of the surface nuclei to form a completely crystallized layer slowed with deeper supercooling. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:Crystal growth from the melt of n-pentacontane (C50) was studied by molecular dynamics simulation. Quenching below the melting temperature gives rise to propagation of the crystal growth front into the C50 melt from a crystalline polyethylene surface. By tracking the location of the crystal-melt interface, crystal growth rates between 0.02 and 0.05 m/s were observed, for quench depths of 10-70 K below the melting point. These growth rates compare favorably with those from a previous study by Waheed et al. [Polymer 2005, 46, 8689-8702]. Next, surface nucleation was identified with the formation of two-dimensional clusters of crystalline sites within layers parallel to the propagating growth front. Critical nucleus sizes, waiting times, and rates for surface nucleation were estimated by a mean first passage time analysis. A surface nucleation rate of ~0.05 nm-2 ns-1 was observed, and it was nearly temperature-independent. Postcritical "spreading" of the surface nuclei to form a completely crystallized layer slowed with deeper supercooling. [ABSTRACT FROM AUTHOR]
ISSN:00249297
DOI:10.1021/acs.macromol.5b02757