Acta Physica Sinica, Volume. 68, Issue 12, 126201-1(2019)
Periclase is the terminal component of the ferropericlase, and its chemical composition is MgO. It is well known that there exists a huge difference between the melting curves of MgO determined experimentally and theoretically. A feasible way to clarify the nature of the melting temperature is to investigate the possible new phase of MgO. Meanwhile, it is very important to study the new phase and the influence of temperature on structural stability of MgO in high-pressure condensed matter physics and geophysics. In the present work, we study in detail the phase stability and the possible existing structures of MgO, which include the structure predicted by particle swarm optimization algorithm through using the first-principles pseudopotential density functional method. We find that MgO crystallizes into a rocksalt structure in a pressure range from 0 to 580 GPa and that the CsCl-type structure is of a high-pressure phase at up to 800 GPa. Although an NiAs-type hexagonal phase perhaps explains the volume discontinuity at (170 ± 10) GPa along the MgO Hugoniot in a shock-compression experiment (Zhang L, Fei Y W 2008 Geophys. Res. Lett.
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Ting Song, Xiao-Wei Sun, Xiao-Ping Wei, Yu-Hua Ouyang, Chun-Lin Zhang, Peng Guo, Wei Zhao.
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Received: Feb. 16, 2019
Accepted: --
Published Online: Oct. 30, 2019
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