Theoretical investigations of the vibrational spectra and hydrogen bond vibrations of two-dimensional ice I

In 2020, experimental observations of a stable two-dimensional (2D) ice I structure on a gold substrate were reported. As an atomic-level material, 2D ice has potential applications in many fields. However, the vibrational spectra of 2D ice I, including its infrared (IR) absorption, Raman scattering, and inelastic neutron-scattering spectra, have not been collected, owing to the complexity of the experimental conditions required to do so. We used first-principle density functional theory calculations to model 2D ice I and proved that it can stably exist without a gold substrate. We also simulated the vibrational phonon density of states and the IR and Raman spectra of 2D ice I. The vibrational frequencies in the translational band of 2D ice I were lower than those of 3D ice, owing to the hydrogen bonds of the former being weaker than those of the latter. The dynamic process analysis of hydrogen bonds showed that the vibrational modes of 2D ice I are quite different with that of 3D ice showing a different vibrational spectrum.