Can the Liquid System Relax Faster Than Its Individual Molecules? – Negative Dipole Correlations Revealed by Molecular Dynamics Simulations

Dielectric studies of many liquids have revealed their ability to develop subtle structural order, reflected in a Kirkwood correlation factor, g_K, dropping below unity. In this letter, we perform molecular dynamics simulations and, for the first time, examine the reorientational dynamics of a system characterized by a g_K value significantly lower than one. To this end, we introduce a novel and breakthrough model of a polar quasi-real molecule, the 2RMSG, that is constructed by merging polar rhombus-like molecule (Sci. Rep. 10, 283 (2020) and Phys. Rev. Lett. 129, 025501 (2020)), with a non-polar one that is complemented with a side group. Our investigations reveal that systems with g_K<1 exhibit dipole-dipole cross-correlations that remain negative throughout the entire time until their decay. By extracting these cross-correlations from the macroscopic correlation functions typically observed in standard experiments, we demonstrate that the overall relaxation of the system proceeds faster than the relaxation of its microscopic self- and cross-components.