Calculation of molecular, dielectric and optical properties of 4′-n-pentyl-4-cyano-biphenyl (5CB)

Using the quantum chemical methods ab initio (B3LYP/6-31 G(D)) and the semi-empirical MOPAC/AM1, the dipoles and their angle with the molecular long axis and the polarizabilities and their anisotropies, have been calculated for different conformers of 5CB. On the basis of these data the dielectric constants and refractive indices and their anisotropies have been calculated, using the Maier-Meier theory. The poor agreement with experimental data could be improved by use of effective dipoles taking account of Kirkwood's g factors, calculated with the theory of Dunmur-Palffy-Muhoray. By calculation of the dispersion of the refractive indices the agreement with the experimental data has been improved. We recommend a procedure for the prediction of dielectric and optical data for nematic compounds, useful for practical application.