Molecular dynamics simulation of the rotational viscosity and its odd-even effect of nematic liquid crystals nCB(4-n-alkyl-4′-cyanobiphenyls, n=5-8)

Based on a full-atomic force field model, molecular dynamics (MD) studies of nCB serials (4-n-alkyl-4'-cyanobiphenyls, n = 5-8) were performed under the isothermal-isobaric NPT ensemble. The second and forth rank order parameters and the orientational. time correlation function(TCF) were obtained by analyzing the trajectory of MD simulation. Then the correlation time was obtained from the fitting of TCF by a single exponential approximation and the rotational diffusion coefficient (RDC) was computed. The rotational viscosity coefficients (RVC) of nCB(n = 5-8) were calculated by Nemtsov-Zakharov and Fialkowski equations, which are based on the statistical-mechanical approach. The odd-even effect of RVC, RDC and the correlation time were discussed separately. Reasonable agreement between the calculated results and the measured data published in literature is obtained, including identical odd-even effect.