Abstract: Whether there is a structural change during yielding was studied by molecular modeling. The results indicate that bond length and bond angle change little while intermolecular interaction dominates the yielding process just as other studies showed. But a structural transition phenomenon called "atom jump" was found during the yielding. The displacements of some atoms exceed ten times of the average displacement of all atoms. In addition, the complexity of polymer chain packing induces the multiple atomic jumps around the yielding point, which can be used to explain properly why polymers have a broad yielding peak.

Key words: Polymer deformation, Yielding, Structural transition, Multiple yieldings