Vibrational mode frequency correction of liquid water in density functional theory molecular dynamics simulations with van der Waals correction.

The frequencies and spectral lineshapes of the stretch and bending modes of water provide invaluable information on the microscopic structures of water in aqueous solutions and at water-solid interfaces. Ab initio molecular dynamics (AIMD) simulation based on density functional theory (DFT) has been used not only for predicting the properties of water but also for interpreting the vibrational spectra of water. Since the accuracy of the AIMD simulations relies on the choice of the exchange-correlation functionals and dispersion correction employed, the predicted AIMD spectra differ significantly, prohibiting the precise comparison of the simulated spectra with experimental data. Here, we simulate the vibrational density of states for liquid water based on various AIMD trajectories. We find that AIMD simulations tend to predict excessive inhomogeneous broadening for the water stretch mode. Furthermore, we develop a frequency correction scheme for the stretch and bending modes of the water, which substantially improves the prediction of the vibrational spectra.