Melting and density of MgSiO3 determined by shock compression of bridgmanite to 1254GPa

Abstract

The essential data for interior and thermal evolution models of the Earth and super-Earths are the density and melting of mantle silicate under extreme conditions. Here, we report an unprecedently high melting temperature of MgSiO3 at 500 GPa by direct shockwave loading of pre-synthesized dense MgSiO3 (bridgmanite) using the Z Pulsed Power Facility. We also present the first high-precision density data of crystalline MgSiO3 to 422 GPa and 7200 K and of silicate melt to 1254 GPa. The experimental density measurements support our density functional theory based molecular dynamics calculations, providing benchmarks for theoretical calculations under extreme conditions. The excellent agreement between experiment and theory provides a reliable reference density profile for super-Earth mantles. Furthermore, the observed upper bound of melting temperature, 9430 K at 500 GPa, provides a critical constraint on the accretion energy required to melt the mantle and the prospect of driving a dynamo in massive rocky planets.

Lower Mantle Melting: Experiments and Thermodynamic Modeling in the System MgO‐SiO2

“…For MgSiO 3 , the melting curve predicted by our model shows a steep initial increase with (Figure 4), closely following the trend of the DAC experiments (Shen & Lazor, 1995; Zerr & Boehler, 1993) to GPa, and, with larger scatter in the data, to GPa, the highest P achieved in Zerr and Boehler (1993), and that of the shock wave experiments by Fei et al. (2021) for much of the lower mantle ‐range (50–80 GPa). However, shock wave experiments (Fei et al., 2021; Fratanduono et al., 2018; Mosenfelder et al., 2009) vary largely in their estimates of the melting curve.…”

“…Melting temperatures from ab‐initio simulations by Di Paola and Brodholt (2016) (DPB16, filled black circles) and the model of de Koker et al., 2013 (dK13, blue squares) as well as melting curves (dashed lines) determined based on shock wave experiments by Fei et al. (2021) (F21, purple) and Mosenfelder et al. (2009) (M09, orange) from ab‐initio simulations by Stixrude and Karki (2005) (SK05, green), and the model by de Koker and Stixrude (2009) (dK09, blue) are included.…”

“…(2021) for much of the lower mantle ‐range (50–80 GPa). However, shock wave experiments (Fei et al., 2021; Fratanduono et al., 2018; Mosenfelder et al., 2009) vary largely in their estimates of the melting curve. At higher , our predicted curve flattens and reaches K at GPa.…”

Thermal Conductivity of Silicate Liquid Determined by Machine Learning Potentials

“…Once we have achieved equilibrated configurations at each volume and temperature, we perform very long NVE (constant number of atoms, volume, and internal energy) simulations, up to 0.5 ns in length. The broad range of pressures and temperature considered, which include some conditions at which the liquid is supercooled (Fei et al, 2021;Fratanduono et al, 2018), are important for gaining a clear picture of the pressure and temperature dependence of the thermal conductivity. We carefully examined the structures and the dynamic properties at all conditions to ensure the system was in the liquid phase.…”

Sub-micrometer focusing setup for high-pressure crystallography at the Extreme Conditions beamline at PETRA III

“…The studies continue with a doubled effort today involving static and dynamic compression methods [e.g. Fei et al (2021)]. However, information characterizing the density alone can rightfully be considered insufficient.…”