Revisiting OD-stretching dynamics of methanol‑d4, ethanol-d6 and dilute HOD/H2O mixture with predefined potentials and wavelet transform spectra

Abstract

• The stretching profiles of OD probes were obtained from classical trajectories. • The normalized frequency distribution and rotational anisotropy are reported. • An accurate and efficient method was reported for the spectral profiles. • The reported results are in an excellent agreement with that of the experiment. Classical molecular dynamics simulations were performed to explore the stretching profiles of hydrogen-bonded liquids using the wavelet transform of classical trajectories to calculate the time-resolved vibrational stretching frequencies of the probes. This method considers the instantaneous distance fluctuations of the unit vector and the momentum along the corresponding bond to calculate the instantaneous stretching frequencies and equilibrium distribution. In this work, we calculated the vibrational spectral properties of the O-D stretch modes in hydrogen-bonding liquids, water, methanol, and ethanol. The time-varying vibrational stretching frequencies of the probes were obtained from the simulated trajectory accurately as compared to other methods. The normalized frequency distribution, time-dependent decay of frequency fluctuations, rotational anisotropy calculations are reported, and relative comparison is made with the existing results. The results of the isotopically diluted HOD mixture and deuterated methanol molecules are in excellent agreement with the experiment, and the ethanol results are satisfactory. This computational method of determining the stretching frequency distribution comparable to the reported vibrational spectrum is one of the complementary accurate theoretical models for the ultrafast vibrational echo spectroscopy experiments. Further, the method can also be adapted to calculate the instantaneous stretching frequency of any probe of interest in a complicated molecular environment.