Dissecting Dielectric Relaxations in Hydrogen-Bonding Solvents via Frequency-Dependent Molecular Motions*

The dielectric relaxations of hydrogen-bonding solvents are poorly understood. Other fluids are correctly described by the single-molecule Debye picture, but the highly ordered hydrogen bonding network of solvent molecules instead leads to a collective response. Developing a new description for hydrogen-bonding fluids requires a connection between the bulk dielectric response and the frequency-dependent molecular motions that produce the observed spectra. These behaviors can be dissected by frequency when an alternating current electrical field is applied directly in molecular dynamics simulations. We explore these motions, the interactions that cause them, and their connection to dielectric relaxation processes in hydrogen-bonding solvents and mixtures of hydrogen-bonding solvents.