Metallic aluminum suboxides with ultra-high electrical conductivity at high pressure

Change log
Pickard, Christopher 
Huang, Tianheng 
Liu, Cong 
Wang, Junjie 
Pan, Shuning 

Aluminum, as the most abundant metallic elemental content in the Earth’s crust, usually exists in the form of alumina (Al2O3). However, the oxidation state of aluminum and the crystal structures of aluminum oxides in the pressure range of planetary interiors is not well established. Here, we predicted two aluminum suboxides (Al2O, AlO) and two superoxides (Al4O7, AlO3) with uncommon stoichiometries at high pressures using first-principles calculations and crystal structure prediction methods. We find that the P4/nmm Al2O becomes stable above ~765 GPa, and may survive in the deep mantles or cores of giant planets such as Neptune. Interestingly, the Al2O and AlO are metallic and have electride features, in which some electrons are localized in the interstitials between atoms. We find that Al2O has an electrical conductivity one order of magnitude higher than that of iron under the same pressure-temperature conditions, which may influence the total conductivity of giant planets. Our findings enrich the high-pressure phase diagram of aluminum oxides and improve our understanding of the interior structure of giant planets.

3402 Inorganic Chemistry, 34 Chemical Sciences, 51 Physical Sciences
Journal Title
Conference Name
Journal ISSN
Volume Title
American Association for the Advancement of Science (AAAS)