MD SIMULATION OF THE ALPHA-DIELECTRIC-RELAXATION OF 2-CHLOROCYCLOHEXYL ISOBUTYRATE

The temperature dependence of the real epsilon' and loss epsilon'' com ponents of the complex dielectric permittivity epsilon of 2-chlorcycl ohexyl isobutyrate, obtained in nonisothermal conditions at several fr equencies, is reported. The calorimetric glass-liquid transition of th e compound is -89 degrees C. The alpha relaxation in the frequency dom ain was obtained at the temperatures sf interest, indirectly from thes e isochrones, and directly from measurements carried our. In isotherma l conditions. The exponent of the stretch KWW function that describes the relaxation is significantly lower in the former case (approximate to 0.40) than in the latter(approximate to 0.58). The MD trajectory of the rotational angle chi(1) defined as the rotation over the ClC-CO b ond of the cyclohexane ring, does not show chair-to-inverse-chair conf ormation transitions at 300 K within a reasonable computing time, high temperatures being necessary to detect them, The time dependent dipol ar autocorrelation coefficient, phi(t), was obtained from the trajecto ries of the dipole moment at 300 and 750 K. The autocorrelation functi on obtained at 300 IC predicts an a relaxation that is rather narrow i n comparison with that determined with the autocorrelation coefficient evaluated at 750 It, The experimental values of the components of the complex dielectric permittivity are in good agreement with those calc ulated using the autocorrelation function evaluated at 750 K.