[S-CG49] Innovation through the Integration of Solid Earth Science and Materials Science

[SCG49-P01] Vibrational property of ice VII from the path integral and Brownian chain molecular dynamics

*Haruhiko Dekura¹, Jun Tsuchiya¹, Motoyuki Shiga² (1.Geodynamics Research Center, Ehime University, 2.Japan Atomic Energy Agency)

Keywords:Ice, Vibrational property, Quantum nuclei effect, Path integral based molecular dynamics

Ice (H₂O) is known to have many crystalline polymorphs under temperature and pressure. Elucidating their structure, physicochemical and vibrational properties is important for physics, chemistry, and planetary science. The small scattering cross section of hydrogen makes it fundamentally difficult to detect experimentally, and experimental constraints to ice's physical properties are still challenging. On the other hand, even in theoretical studies based on the standard ab initio approach, information on the quantum behavior of hydrogen on the physical and chemical properties is limited due to difficulty in precisely accounting for the quantum nature. Recently, we initiated an ab initio computational study for the vibrational properties of ice to clarify the quantum dynamical behavior and its contribution to free energy. In general, the nuclear quantum effects producing the tunneling phenomenon and proton delocalization significantly increase the anharmonicity in the force field around hydrogen atoms, which in turn can greatly affect the vibrational properties of the hydrogen-bonded systems. To consider the characteristic quantum features properly, we employed one of the modern computational approaches, the ab initio path integral molecular dynamics method combined with Brownian chain molecular dynamics (Shiga+2022). As a starting point for the future development of our research project, we calculated the vibrational spectrum of ice VII at ambient condition. In this presentation, we show the calculated spectrum with a comparison with the infrared measurements and discuss the applicability of our computational method for studying high-pressure ice phases. Physical property arising from the quantum nuclei effect is also discussed.