Comparison of different potential models in the calculations of the infrared and polarized Raman spectra and the transient infrared absorption anisotropy of the OH stretching mode of liquid water

摘要

The infrared (IR) and polarized Raman spectra of the OH stretching mode of neat liquid H2O, as well as the time dependence of the transient IR (TRIR) absorption anisotropy of the same vibrational mode of both neat liquid H2O and a dilute liquid mixture of H2O/HDO/D2O, are calculated by using four widely-used potential models (SPUE, TIP3P, TINP, and TIP5P) to see the effects of the difference in the treatment of electrostatic interactions on the calculated spectral profiles. In the calculations, three important factors for simulating vibrational spectra of coupled-oscillators systems in the liquid state (frequency shifts and fluctuations of individual molecules, resonant vibrational couplings between molecules, and liquid dynamics) are taken into account with a time-domain computational method. It is shown that, although the calculations with all the four potential models commonly reproduce the main observed spectral features, there are also some significant differences. Those differences are partly a matter of the calculated magnitudes of the electric fields operating on OH bonds from hydrogen-bonded molecules, and are discussed in relation to the differences in the calculated radial distribution function. It is also shown that the time constant of the long-time decay (in the region of t >= 1.5 ps) of the TRIR anisotropy in a dilute liquid mixture of H2O/HDO/D2O is calculated as 2.7-2.8 ps by using the SPC/E and TIP5P potentials, in reasonable agreement with the experimental results in the literature. An improved and self-consistent treatment of the electric field-induced enhancement of dipole derivatives, which is another important factor for simulating the OH stretching band of liquid water, is also proposed. (c) 2007 Elsevier B.V. All rights reserved.