Understanding Dielectric Loss in Water via Distance-Dependent Dipole Correlation Functions

Abstract

We present a molecular dynamics study revealing that dielectric loss in liquid water in GHz region arises not from isolated molecular rotations, but from collective dipolar correlations spanning more than tens of molecules. By introducing a distance-dependent dipole correlation function, we quantify the spatial extent and temporal evolution of orientational fluctuations contributing to dielectric relaxation. Three distinct peaks identified in the dipole vector correlation at 0.25 nm, 0.53 nm, and 0.75 nm-corresponding to coordinated reorientation among approximately 70 water molecules-indicate a strong link between molecular structure and dielectric behaviour. These findings provide a microscopic basis for understanding dielectric absorption and offer new insights into the design of water-based dielectric systems.