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Atomistic Details Of Disordering Processes in SuperheatedPolymethylene Crystals II. Effects of Surface Constraints

Published online by Cambridge University Press:  15 February 2011

B. Wunderlich ,
G. L. Liang ,
B. G. Sumpter  and
D. W. Noid
B. Wunderlich
Affiliation:
Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, and Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6197.
G. L. Liang
Affiliation:
Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, and Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6197.
B. G. Sumpter
Affiliation:
Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, and Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6197.
D. W. Noid
Affiliation:
Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, and Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6197.
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Abstract

Atomistic details of disordering in superheated polymethylene crystals havebeen studied using full molecular dynamics simulations of crystalscontaining 9600 CH2-groups. The crystal size was about 227 nm3 Simulations were carried out for up to 100 ps, starting attemperatures about 100 K above the melting temperature. Typically 1.5 h ofCPU time on a Cray X-MP were necessary per ps simulation. Superheatingcauses a quick development of large-scale disorder throughout the crystal,including reorientation, translation, and the destruction of crystalsymmetry. This is followed ultimately by surface Melting. Crystallizationcenters with hexagonal packing are found in superheated, unconstrainedcrystals. On cooling during the simulation, recrystallization processescompete with the disordering, resulting in a reorientation of the molecularchains and reorganization of the crystal. Neither the fully amorphous phasenor the ordered crystal are reached during these short-time simulationsusing an instantaneous temperature increase to above the meltingtemperature, followed by a slow cooling into the crystallization temperatureregion.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 321: Symposium E – Crystallization and Related Phenomena in Amorphous Materials—Ceramics, Metals, Polymers, and Semiconductors , 1993 , 93
Copyright
Copyright © Materials Research Society 1994

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References

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