Birefringence, polarizability order parameters and DFT calculations in the nematic phase of two bent-core liquid crystals and their correlation

This article presents the optical and electrostatic potential studies of two fluorinated liquid crystalline compounds. Birefringence, molecular polarizability and order parameter are most essential studies in the liquid crystal research. The compounds selected for studies are bent-core calamitic type and was verified by the density functional theory (DFT) approach . Using DFT approach, Electrostatic Potential (ESP) and Homo-Lumo energy gap of these compounds were studied. ESP study and the energy gap between the compounds explain and justify the refractive indices, birefringence and polarizability trends of the compounds more accurately. It was observed that the values of refractive indices and birefringence depend on the electronegativity. For optical measurements, thin prism technique has been used to obtain the experimentally observed refractive indices by using a He-Ne laser of wavelength 633 nm. Using four parameters theoretical model, the experimentally measured refractive indices and birefringence results were compared and found to fitted properly. Vuk's and Neugebauer's methods have also been employed to study the polarizabilities of the compounds. From this study, it is found that both the theoretical model can be validated for bent-core calamitie compounds. Macroscopic and microscopic order parameters and different field factors are also reported in this article.