Infrared and Raman spectra of water under pressure via first principles molecular dynamics

Ikeda, Takashi

Molecular vibrational spectroscopies via infrared (IR) absorption or Raman scattering are widely employed to explore possible phases of materials under study irrespective of their thermodynamic states. Tominaga successfully performed the IR and Raman experiments for ambient and supercritical water. They found that a peak corresponding to the bending mode observed around 1600 cm for ambient water vanishes from the Raman spectrum of supercritical water, while the corresponding peak remains clearly visible in the measured IR spectrum. This observation cannot be explained unless dynamical and electronic properties of water under pressure are considered explicitly. Thus, in this contribution, a theoretical formulation is developed for computing the IR and Raman spectra via first principles molecular dynamics. Then we demonstrate that the above-mentioned experimental findings for water are well reproduced in our computational scheme.