Ab-Initio Crystallization of Alkanes: Structure and Kinetics of Nuclei Formation

Molecular dynamic simulations of the crystallization
of eicosane have been carried out as an example
of a low molecular weight n-alkane system
and for a high molecular weight alkane as an analog
of a semi-crystalline polyethylene. An alternative
method for determining crystal domains and
growing nuclei has been developed based on the
eicosane system behavior. In the former case, density
and crystal lattice parameters conformed well
to previously reported experimental values. Moreover,
crystallization and nuclei formation were
monitored using a procedure developed herein.
Analysis showed that metastable nuclei could be
obtained at 250 K lasting appreciably long lifetimes
of tens to hundreds of nanoseconds, which
then exhibited an abrupt irreversible increase in
size. The present study emphasizes the long quasiequilibrium
of these crystallizing systems even at
moderate supercooling.