Determination of self and cross contributions to the dipole-dipole correlations function from analysis of dielectric measurements

The nonexponential nature of the structural relaxation is one of the most characteristic features of the molecular dynamics in glass-forming liquids. Various experimental techniques can be employed to probe this process; however, broadband dielectric spectroscopy (BDS) is the most frequently used. Based on MD simulations, we provide strong evidence of bi-modal nature of the dielectric loss peak of primary relaxation. Further, we point out that the primary dielectric relaxation process measured at constant displacement D is dominated by the self-correlation term in the dipole-dipole correlation function. In practice, it means that the dielectric spectra should be presented in the dielectric modulus representations to disclose the spectral features of the self mode.