New MgO–H2O compounds at extreme conditions

Abstract

The reaction of water and other materials has been the central topic under high-pressure physics research, because the Earth, super-Earth, Uranus, Neptune and other planets contain a great amount of water inside. However, the reaction between star-rich MgO and water under ultra-high pressure remains still poorly understood. Here, using ab initio evolutionary structure prediction researches of the structures of MgO–H2O system at 300 GPa–600 GPa, we find that (MgO)2H2O and MgO(H2O)2 could become stable. The (MgO)2H2O compounds may be an important component of super-Earth and the ice-rock boundary of Uranus and Neptune. Furthermore, it may be the reservoir under high pressure before the forming of the Earth’s core or other super-Earths. The current findings could expand our knowledge and improve our understanding of the evolution and composition of planets.