Molecular dynamics (MD) simulation has been performed on the crystallization process of a single polyethylene chain from fully extended state in the vacuum at different temperatures (100500K with an interval of 100K). The results indicated that each of the simulated crystallization processes consists of three stages. The first stage is a self-cohesion stage

in which the extended chain collapsed to a coil with a sharp decrease of energy and size of the chain. The second stage is an ordering stage in which a lamella was formed by the chain in the way of the adjustment of the chain segments.The last stage is adjusting stage

where the energy and the order keep almost constant

but the lamella shape varies to some extent.Even though there is a big gap in the time scale between MD simulation and laboratory experiments

the fratures of the simulated three stages were very similar to the three stages for bulk polymers in usual crystallization (the nucleation

the crystal gtrowth and the perfection stage).The collapse process of extended chain proceeded via a two-step mechanism at 100K and 500K: a local collapse

forming conpact domains

which subsequently coalesce to yield a fully collapsed state.It was found that the segments in the domains formed in local collapse step were ordered packed at 100K

while the randomly packed at 500K.The self-cohesion rate of the chain is found intensively dependent on the crystallization temperature.The higher temperature resulted in the faster cohesion process.The crystallization temperature also influenced the thickness of the final lamellae.The thicker lamella structure is likely formed at lower temperature.This is different from the crystallization process of polyethylene bulk.