Ab initio prediction of an order-disorder transition in Mg$_2$GeO$_4$: implication for the nature of super-Earth's mantles

Koichiro Umemoto; Renata M. Wentzcovitch

doi:10.1103/PhysRevMaterials.5.093604

paper

Ab initio prediction of an order-disorder transition in Mg $_{2}$ GeO $_{4}$ : implication for the nature of super-Earth's mantles

arXiv:2012.08056 · doi:10.1103/PhysRevMaterials.5.093604

Abstract

Here we present an ab initio prediction of an order-disorder transition (ODT) from $I 4 ˉ 2 d$ -type to a Th $_{3}$ P $_{4}$ -type phase in the cation sublattices of Mg $_{2}$ GeO $_{4}$ , a post-post-perovskite (post-PPv) phase. This uncommon type of prediction is achieved by carrying out a high-throughput sampling of atomic configurations in a 56-atom supercell followed by a Boltzmann ensemble statistics calculation. Mg $_{2}$ GeO $_{4}$ is a low-pressure analog of $I 4 ˉ 2 d$ -type Mg $_{2}$ SiO $_{4}$ , a predicted major planet-forming phase of super-Earths' mantles. Therefore, a similar ODT is anticipated in $I 4 ˉ 2 d$ -type Mg $_{2}$ SiO $_{4}$ as well, which should impact the internal structure and dynamics of these planets. The prediction of this Th $_{3}$ P $_{4}$ -type phase in Mg $_{2}$ GeO $_{4}$ enhances further the relationship between the crystal structures of Earth/planet-forming silicates and oxides at extreme pressures and those of rare-earth sesquisulfides at low pressures.

Ab initio prediction of an order-disorder transition in Mg $_{2}$ GeO $_{4}$ : implication for the nature of super-Earth's mantles

Abstract

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Ab initio prediction of an order-disorder transition in Mg2​GeO4​: implication for the nature of super-Earth's mantles

Abstract

References in corpus (8)

Cited by in corpus (3)

Ab initio prediction of an order-disorder transition in Mg $_{2}$ GeO $_{4}$ : implication for the nature of super-Earth's mantles