Structure and Dynamics of Water Ice Ih

Water ice Ih is a non-periodic system with proton disorder due to the large number of possible configurations of hydrogen atoms that follow the ice rule. Understanding the structure and dynamics of water ice Ih is important for various scientific and technological applications. In this work, we measured the static and dynamic structure factors of a single crystal ice Ih at different temperatures using elastic and inelastic neutron scattering techniques. We showed that our static structure factors could be well explained by the Fourier transform of the simulated spatial configurations of water ice.

We derived the formula to calculate the dynamic structure factor of non-periodic systems. We showed the limitations of classical first-principle phonon calculations when dealing with non-periodic systems. We presented a novel method to calculate the dynamics of water ice Ih. We constructed the force constant matrices using a mathematical model based on the local symmetry guaranteed by the ice rule. The model parameters were first fitted to first-principle phonon results and then fine-tuned to fit the neutron scattering data. Our results showed the detailed short-range interactions of water ice Ih with high accuracy and corrected the underestimated hydrogen bond strengths using classical first-principle phonon calculations. Our results provided new insights into the lattice dynamics and thermal properties of water ice Ih and offered potential applications for understanding other non-periodic systems with local symmetry.