Quantum chemical calculations in industrial liquid crystal research

In advance to syntheses in the laboratory, it is very useful, to have quick and easy procedures available, allowing the calculation of physical properties of liquid crystal materials without any experimental basis. Using different quantum chemical methods, it is possible to calculate molecular data like electrical dipole moment and polarizability including the anisotropy of these data. By comparison of the results of ab-initio and semiempirical methods it can be shown, that the latter are timesaving and reliable enough for prediction of data for applications. In order to calculate dielectric properties of nematic liquid crystals, the necessary data of molar volumes and order parameters can be obtained by empirical methods without measurements. One major problem is the calculation of effective electrical dipole moments, taking in consideration the association in compounds with large dipole moments. The results of different approaches for this purpose are compared and discussed. Because approaches found in the literature fail in the case of large dipole moments, a new procedure taking in account attractive and repulsive energies of the dipole-dipole interaction has been developed. In order to improve the agreement of calculated optical data with experimental data, the dispersion of the polarizability is taken into account.