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Prediction of an U2S3-type polymorph of Al2O3 at 3.7 Mbar.

ABSTRACT: We predict by first principles a phase transition in alumina at approximately 3.7 Mbar and room temperature from the CaIrO(3)-type polymorph to another with the U(2)S(3)-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(2)O(3)(II)-type structure and the Rh(2)O(3)(II)-type to CaIrO(3)-type structure. The transformation to the U(2)S(3)-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 planet-forming minerals might be related to that of the rare-earth sulfides.

SUBMITTER: Umemoto K

PROVIDER: S-EPMC2373319 | biostudies-literature | 2008 May

REPOSITORIES: biostudies-literature

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Prediction of an U2S3-type polymorph of Al2O3 at 3.7 Mbar.

Umemoto Koichiro K Wentzcovitch Renata M RM

Proceedings of the National Academy of Sciences of the United States of America 20080501 18

We predict by first principles a phase transition in alumina at approximately 3.7 Mbar and room temperature from the CaIrO(3)-type polymorph to another with the U(2)S(3)-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: ...[more]

PMID: 18451030

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