Charge layering in polar liquids

Evidence of a moderate charge layering is found in simulated liquids of rigid polar molecules (acetone and acetonitrile), while this correlation is absent if molecules are flexible (1,2-dimethoxyethane). This effect is originated by the packing of rigid bodies, as the charge and density oscillations are in phase and the separation between two maxima corresponds to the size of the molecules. Electrostatic interactions among the partial charges of the site-site model potential act as a small perturbation on the liquid structure and so on this charge layering, while they are the driving forces of the corresponding feature of simple molten salts. The structures of liquids formed by flexible chain polar molecules are more disordered, with more uniform space distribution, and no charge layering results.