Isotropic seismic velocities of stishovite to post-stishovite along a model mantle geotherm (Brown & Shankland 1981). Shaded regions are bounded by the Reuss and Voigt estimates, solid line represents the Voigt–Reuss–Hill average. Room temperature and 1073 K |$V_P$|⁠, |$V_{\Phi }$| and |$V_S$| data from Chen et al. (2024) (which is assumed to closely approximate the Voigt–Reuss–Hill velocities) is also shown with error bars. The top axis shows the pressures and temperatures along the geotherm.