The hypothetical signature of self aggregation in the low frequency response of aqueous solutions: A molecular dynamics simulation analysis

Starting from the distribution of urea molecules given by different intermolecular interaction potential models, we analyze how these distributions affect the low frequency response of urea aqueous solutions. Our main concern in this paper is to analyze the hypothetical signature of the self-aggregation process (strong urea-urea interaction) in the low frequency response. The main hypothesis is the interpretation of the low frequency response of these aqueous solutions as a result of both the spectral contribution of the translation and rotational motions of urea molecules and the spectral contribution of the translation motion of water molecules. The analysis indicates that the signature of the self aggregation in the low frequency response in aqueous solutions is difficult to characterize because it induces a small shift of the spectral densities associated with the translation and rotation motion of solute and water molecules. However it was shown that a strong solute-water interaction induces a large shift of these spectral densities to higher frequencies.