Atomistic and Ab initio modeling of CaAl2O4 high-pressure polymorphs under Earth’s mantle conditions
- Authors: Eremin N.N.1, Grechanovsky A.E.2, Marchenko E.I.1
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Affiliations:
- Faculty of Geology
- Institute of Geochemistry
- Issue: Vol 61, No 3 (2016)
- Pages: 432-442
- Section: Lattice Dynamics and Phase Transitions
- URL: https://journals.rcsi.science/1063-7745/article/view/190013
- DOI: https://doi.org/10.1134/S1063774516030111
- ID: 190013
Cite item
Abstract
Semi-empirical and ab initio theoretical investigation of crystal structure geometry, interatomic distances, phase densities and elastic properties for some CaAl2O4 phases under pressures up to 200 GPa was performed. Two independent simulation methods predicted the appearance of a still unknown super-dense CaAl2O4 modification. In this structure, the Al coordination polyhedron might be described as distorted one with seven vertices. Ca atoms were situated inside polyhedra with ten vertices and Ca–O distances from 1.96 to 2.49 Å. It became the densest modification under pressures of 170 GPa (density functional theory prediction) or 150 GPa (semi-empirical prediction). Both approaches indicated that this super-dense CaAl2O4 modification with a “stuffed α-PbO2” type structure could be a probable candidate for mutual accumulation of Ca and Al in the lower mantle. The existence of this phase can be verified experimentally using high pressure techniques.
About the authors
N. N. Eremin
Faculty of Geology
Author for correspondence.
Email: neremin@geol.msu.ru
Russian Federation, Moscow, 119992
A. E. Grechanovsky
Institute of Geochemistry
Email: neremin@geol.msu.ru
Ukraine, Kyiv, 03680
E. I. Marchenko
Faculty of Geology
Email: neremin@geol.msu.ru
Russian Federation, Moscow, 119992