Structures of the newly predicted magnesium oxides: On the left, MgO2; on the right, Mg3O2. Green – Mg atoms, red – O atoms. Isosurfaces show regions of high electron localization.
A team of researchers led by Artem R. Oganov, a professor of theoretical crystallography in the Department of Geosciences, has made a startling prediction that challenges existing chemical models and current understanding of planetary interiors—magnesium oxide, a major material in the formation of planets, can exist in several different compositions. The team’s findings, “Novel stable compounds in the Mg-O system under high pressure,” are published in the online edition of Physical Chemistry Chemical Physics. The existence of these compounds—which are radically different from traditionally known or expected materials—could have important implications.
“For decades it was believed that MgO is the only thermodynamically stable magnesium oxide, and it was widely believed to be one of the main materials of the interiors of the Earth and other planets,” said Qiang Zhu, the lead author of this paper and a postdoctoral student in the Oganov laboratory.
“We have predicted that two new compounds, MgO2 and Mg3O2, become stable at pressures above one and five million atmospheres, respectively. This not only overturns standard chemical intuition but also implies that planets may be made of totally unexpected materials. We have predicted conditions (pressure, temperature, oxygen fugacity) necessary for stability of these new materials, and some planets, though probably not the Earth, may offer such conditions,” added Oganov.
In addition to their general chemical interest, MgO2 and Mg3O2 might be important planet-forming minerals in deep interiors of some planets. Planets with these compounds would most likely be the size of Earth or larger.
Read more at: Phys.org