Density of Phonon States in Cubic Ice Ic

The measurement of the H-projected density of phonon states (H-DOPS) of polycrystalline ice Ic has been performed with an unprecedented accuracy, and in a sample having an almost perfect crystallographic purity, as it was obtained from the transformation of ice XVII. Results are compared with new accurate measurements of H-DOPS in ice Ih, and with centroid molecular-dynamics (MD) computations. The differences between the experimental H-DOPS in these two forms of ice are subtle, but quantitatively measurable. In addition, they are reproduced semi-quantitatively by computational methods, demonstrating the effectiveness of this innovative simulation tool for reproducing the dynamical properties of the ice structures.