Non-Gaussian behavior of crystalline and amorphous phases of polyethylene

We report on measurements of the incoherent elastic neutron-scattering intensity Iel(Q) of polyethylenes with degrees of crystallinity 0.46 and 0.96 in a wide Q ~length of scattering vector! range from 0.4 to 6.2 Å to observe the deviation from the Gaussian behavior. The non-Gaussian behavior was observed in both the amorphous and the crystalline phases. The non-Gaussian behavior in the theoretically well-known crystalline phase can be understood more or less quantitatively in terms of the anisotropy of the mean-square displacement. The result implies that at least a part of the non-Gaussian behavior of the amorphous phase is due to the same source, while another part may be due to the dynamical heterogeneity inherent to the amorphous phase.