Fig. 6

The calculated and experimental elastic constants of high-pressure ice VIII, VII, and X (Tsuchiya and Tsuchiya 2017; Zhang et al. 2019; Shi et al. 2021; Ahart et al. 2011). The full lines with full symbols indicate the calculated elastic constants of ice VIII containing asymmetric hydrogen bond. Dashed lines indicate the elastic constants of ice X with symmetric hydrogen bond. Note that ice VIII and ice VII have tetragonal and cubic crystal symmetries, respectively, and the index of the elastic constants are different (e.g., C\(_{33}\) of ice VIII corresponds to C\(_{11}\) in ice VII and X)