Shock Response and Phase Transitions of MgO at Planetary Impact Conditions

TL;DR

This study investigates MgO's behavior under extreme pressures and temperatures relevant to planetary impacts, revealing phase boundaries and melting conditions crucial for understanding moon formation.

Contribution

The paper combines high-precision shock experiments and advanced quantum simulations to map MgO's phase diagram up to 1.2 TPa and 42,000 K, providing new insights into planetary impact conditions.

Findings

Solid-solid and solid-liquid phase boundaries identified.

Complete melting occurs above 600 GPa.

Solid and liquid phases coexist over a wide pressure range.

Abstract

The moon-forming impact and the subsequent evolution of the proto-Earth is strongly dependent on the properties of materials at the extreme conditions generated by this violent collision. We examine the high pressure behavior of MgO, one of the dominant constituents in the earth's mantle, using high-precision, plate impact shock compression experiments performed on Sandia National Laboratories Z-Machine and extensive quantum simulations using Density Functional Theory (DFT) and quantum Monte Carlo (QMC). The combined data span from ambient conditions to 1.2 TPa and 42,000 K, showing solid-solid and solid-liquid phase boundaries. Furthermore our results indicate under impact that the solid and liquid phases coexist for more than 100 GPa, pushing complete melting to pressures in excess of 600 GPa. The high pressure required for complete shock melting places a lower bound on the relative velocities required for the moon forming impact.