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Shock Response and Phase Transitions of MgO at Planetary Impact Conditions
Seth Root1, Luke Shulenburger1, Raymond W Lemke1
1Sandia National Laboratories, Albuquerque, New Mexico 87185, USA.
Physical Review Letters
|November 21, 2015
Summary
Magnesium oxide (MgO) under extreme pressure reveals that complete melting requires over 600 GPa. This finding impacts understanding of planetary collisions and early Earth evolution.
Area of Science:
- Planetary Science
- High-Pressure Geophysics
- Materials Science
Background:
- The moon-forming impact subjected proto-Earth materials to extreme conditions.
- Understanding the behavior of Earth's mantle constituents under these conditions is crucial.
Purpose of the Study:
- To investigate the high-pressure behavior of magnesium oxide (MgO), a key mantle component.
- To determine solid-solid and solid-liquid phase boundaries of MgO under impact conditions.
Main Methods:
- High-precision plate impact shock compression experiments on Sandia National Laboratories' Z Machine.
- Extensive quantum calculations using density functional theory (DFT) and quantum Monte Carlo (QMC) methods.
- Combined data spanning ambient conditions to 1.2 TPa and 42,000 K.
Main Results:
- Solid and liquid phases of MgO coexist for pressures exceeding 100 GPa under impact.
- Complete shock melting of MgO is determined to occur at pressures above 600 GPa.
- Phase boundaries were mapped across a wide range of extreme pressures and temperatures.
Conclusions:
- The high pressure required for complete MgO melting has significant implications for planetary collision models.
- Results inform our understanding of material behavior during the moon-forming impact and early Earth evolution.
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