[S-CG58] 固体地球科学と材料科学の融合が切り拓く新展開

[SCG58-P04] Vibrational properties of high-pressure ice: Path integral and Brownian chain molecular dynamics approach

*出倉 春彦¹、土屋 旬¹、志賀 基之² (1.愛媛大学地球深部ダイナミクス研究センター、2.人日本原子力研究開発機構)

キーワード：Ice、Vibrational property、Quantum nuclei effect、Path integral based molecular dynamics

Ice (H₂O) exhibits various crystalline polymorphs under high pressure. Understanding their structure, physicochemical, and vibrational properties is crucial in physics, chemistry, and planetary science, but hydrogen’s small scattering cross-section makes experimental characterization challenging. Moreover, standard ab initio approaches often fail to capture nuclear quantum effects, such as tunneling and proton delocalization, which significantly impact vibrational properties. Very recently, we have successfully calculated the vibrational spectra of ice VII and X under high pressure using the ab initio path integral molecular dynamics method (J. Tsuchiya et al., 2024) combined with the Brownian chain molecular dynamics approach (M. Shiga et al., 2022). In this presentation, we discuss the quantum effects on the spectra in detail. The spectral changes across the VII/X phase transition are also examined in detail. Our results provide deeper insight into the quantum nature of hydrogen-bonded networks and pave the way for accurate free energy calculations of high-pressure ice.