Fig. 2: Structural data of investigated systems.
From: Structural independence of hydrogen-bond symmetrisation dynamics at extreme pressure conditions
a Equation of state (EOS) data of the different hydrogen-bonded phases. We use the EOS for H2O ice-VII/X (gray graphs) of from22, based on ab-initio computations and the XRD based EOS of21 for δ-AlOOH (green graphs). The other curves are based on third order Birch-Murnagham EOS fits to our diffraction data for iron-bearing δ-AlOOH (brown graphs) and phase-D (blue graphs). δ-(Al0.3,Fe0.7)OOH exhibits a 7% volume collapse associated to the electron spin crossover of ferric iron (c.f. Fig. 4a). b Oxygen-oxygen distance (rOO) as a function of P. Different pressure dependencies of the Qi(i = 3, 5, 6) (red, brown and yellow graphs respectively) H-bond environments in δ-(Al,Fe)OOH20 were estimated through interpolation of rOO between endmembers δ-AlOOH10, 21 and ϵ-FeOOH25 with respect to the local iron content. We only consider the high spin state in iron bearing phases, as the spin transition occurs at significantly higher P ( ~45 GPa) than the hydrogen-bond symmetrization (~15 GPa).
