Intermolecular charge fluxes and terahertz spectral features of liquid methanol

Abstract

The behavior of electrons that is relevant to the THz spectral features of liquid methanol is examined theoretically through analyses of the dipole derivatives and the electron density derivatives with respect to the molecular translations and rotations of hydrogen-bonded methanol. It is shown that the hydrogen-bond-induced components of these derivatives are reasonably well interpreted or modeled by intermolecular charge fluxes through hydrogen bonds, which represent the modulations of the extent of hydrogen-bond-induced intermolecular charge transfer occurring upon fluctuations of hydrogen-bond lengths. Combining this model with classical molecular dynamics, spectral simulations in the 0–1000 cm−1 region are carried out, resulting in reasonably good agreement with the observed overall spectral features. The spectral simulations are based on two different formulas that are suitable for different ways of spectral decomposition. The factors with regard to intensity generation and molecular motion that are important for each element of the spectral features are discussed.