“…On the contrary, V P derived from the phonon density of states measured by NRIXS up to 153 GPa (Mao et al, 2001) plots higher than shock wave determination (Brown and McQueen, 1986), indicating possible temperature effects, and extrapolates at core pressures to V P higher than PREM. Later NRIXS and IXS studies, with progressively improved beamline performance (flux, focusing optics), improved statistics and improved sample environment (hydrostaticity and/or texture characterization), focused on anisotropy (Antonangeli et al, 2004b;Lin et al, 2010), high-temperature effects (Lin et al, 2005;Kantor et al, 2007;Antonangeli et al, 2008;Antonangeli et al, 2012;Ohtani et al, 2013), or effect of nickel and/or light element inclusion (Lin et al, 2003;Badro et al, 2007;Kantor et al, 2007;Gao et al, 2008;Fiquet et al, 2009;Antonangeli et al, 2010;Shibazaki et al, 2012;Kamada et al, 2014). In view of the specific characteristics of the two techniques and of the respective data analysis, today's general consensus is that, for measurements on polycrystalline samples, IXS provides more reliable V P and NRIXS more reliable V S (the Debye velocity measured directly by NRIXS is more heavily weighted in the determination of V S , while V P determination is more dependent on the used equation of state; in comparison, IXS provides a direct determination of V P while V S depends on the choice of equation of state).…”