Elastic line energies and line tensions of dislocations in polyethylene crystals

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Abstract
The elastic line energies and tensions of dislocations in the {100} planes of a polyethylene crystal are rigorously calculated taking the anisotropy of the crystal fully into account and allowing for uncertainties in the values of the elastic constants. The results are used to substantiate previous qualitative conclusions concerning the behaviour of dislocations in polyethylene crystals (Shadrake and Guiu 1976). In particular it is found that the [001] screw dislocation has even higher line tension than previously estimated, and it is concluded that homogeneous nucleation by thermal fluctuations is the most likely source of such dislocations. As a consequence the stress required to produce chain-axis slip is not only a function of deformation temperature but must also be strongly dependent upon the crystal thickness.
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