Simulation of the intermolecular vibrational spectra of liquid water and water clusters

We report simulated Raman and infrared spectra of liquid water and water clusters in the frequency range 0–1000 cm−1. The librational peak in the Raman spectrum of the liquid, which has a strong dependence on the anisotropy of the assumed gas-phase polarizability tensor, allows us to choose between various models for that tensor. Most of the spectroscopically probed dynamics of the liquid are present in the small clusters, with N as low as 5. The librational peaks in the pentamer spectra are shown to redshift with increasing temperature.