We predict by first principles a phase transition in alumina at ≈3.7 Mbar and room temperature from the CaIrO3-type polymorph to another with the U2S3-type structure. Because alumina is used as window material in shock-wave experiments, this transformation should be important for the analysis of shock data in this pressure range. Comparison of our results on all high-pressure phases of alumina with shock data suggests the presence of two phase transitions in shock experiments: the corundum to Rh 2O3(II)-type structure and the Rh2O 3(II)-type to CaIrO3-type structure. The transformation to the U2S3-type polymorph is in the pressure range reached in the mantle of recently discovered terrestrial exoplanets and suggests that the multi-megabar crystal chemistry of planetforming minerals might be related to that of the rare-earth sulfides.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - May 6 2008|
- First-principles calculation
- High-pressure phase transition
- Rare-earth sulfide structure