Presentation Information
[15a-PA5-12]Ab Initio Study of Optical Anisotropy and Strain-Induced Effects in Crystalline Polyethylene
〇Takayuki Nishio1, Hiroya Nitta1, Taku Ozawa1 (1.JSOL CORP.)
Keywords:
polymer,optical anisotropy,strain
This study evaluates changes in dielectric constant and refractive index tensors during polymer deformation. Initially, a 1,220-atom amorphous polyethylene (PE) model confirmed that uniaxial stretching increases the refractive index along the stretching direction. To understand this origin, we analyzed a PE unit crystal model under 1–5% strain.Dielectric constants were evaluated using the independent particle approximation (IPA) and density functional perturbation theory (DFPT). The results showed that computational approximations significantly influence the predicted anisotropy. DFPT analysis revealed that electronic polarization along the chain axis (z-axis) increases under strain. Analysis of the density of states (DOS) and optical spectra indicated that the anisotropy arises from changes in both the joint density of states (JDOS) and local polarization. This report provides a mechanistic understanding of optical anisotropy by decoupling these physical contributions in both amorphous and crystalline models.