The relative permittivity of dimethyl sulfoxide (DMSO) solutions, ethanol (C2H5OH) solutions and their mixtures have been measured at 20 ℃, respectively. Surprisingly, at certain concentration, it appears an exceptional phenomenon that the imaginary part of mixtures relative permittivity is larger than that of their pure components. To explain the exceptional phenomenon on the mixtures relative permittivity, a systematical investigation about the molecular clusters ((DMSO)m(C2H5OH)n) as well as their cluster radii have been given using DFT calculations. Comparing the cluster radii of the binary clusters ((DMSO)m(C5H5N)n) with that of the pure clusters ((DMSO)m and (C2H5OH)n), the results have given an reasonable explanation of the exceptional phenomenon on the imaginary part of the mixtures relative permittivity.
