Anisotropy in dielectric properties of polyvinylidene fluoride

The first principles calculations have been performed for the ferroelectric β-phase of the semi-crystalline polymer Polyvinylidene fluoride (PVDF). The electronic structure and the dielectric properties have been investigated using density functional theory (DFT). Hybrid functionals give better results for band gap as compared to generalized gradient approximation (GGA) and local density approximation (LDA). It is found that β-phase has a band gap of 6.5 eV at the Γ-point which is in good agreement with the experimental results. The dielectric properties of polar form (I) and (II) have been analyzed using density functional perturbation theory (DFPT). An anisotropy has been observed in the dielectric permittivity of crystalline PVDF. The microscopic investigation of these properties helps in better understanding and hence improving the energy density in energy storage devices.