Systematic investigations of Infrared spectra of liquid water by first-principles methods

The infrared spectroscopy (IR) is a powerful experimental technique to probe the dynamic dipole fluctuations of water molecules, which are strongly correlated through the H-bond network of liquid water. Here, we compute the infrared spectra of liquid water based on ab initio molecular dynamics simulations by using maximally localized Wannier functions as basis, in which both the generalized gradient approximations (GGA) level exchange-correlation (XC) functional and meta-GGA level strongly constrained and appropriately normed (SCAN) XC functionals are employed. For comparison, the vibration frequencies of the water vapor are computed as well. Our theoretical studies show that the theoretical predictions of spectral features are systematically improved by better liquid water structural predictions through the more physical description of H-bond strengths as well as the capture of intermediate range van der Waals interactions by the SCAN meta-GGA functional.