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Microscopic origin of pressure-induced isosymmetric transitions in fluoromanganate cryolites
Journal article   Open access   Peer reviewed

Microscopic origin of pressure-induced isosymmetric transitions in fluoromanganate cryolites

Nenian Charles and James M. Rondinelli
Physical review. B, v 90(9)
24 Sep 2014
url
https://link.aps.org/accepted/10.1103/PhysRevB.90.094114View
Published, Version of Record (VoR) Open

Abstract

Materials Science Materials Science, Multidisciplinary Physical Sciences Physics Physics, Applied Physics, Condensed Matter Science & Technology Technology
Using first-principles density functional theory calculations, we investigate the hydrostatic pressure-induced reorientation of the Mn-F Jahn-Teller bond axis in the fluoride cryolite Na3MnF6. We find that a first-order isosymmetric phase transition (IPT) occurs between crystallographically equivalent monoclinic structures at approximately 2.15 GPa, consistent with earlier experimental studies. Mode-crystallography analyses of the pressure-dependent structures in the vicinity of the transition reveal a clear evolution of the Jahn-Teller bond distortions in cooperation with an asymmetrical stretching of the equatorial fluorine atoms in the MnF6 octahedral units. We identify a significant (70%) change in the orbital occupancy of the e(g) manifold of the 3d(4) Mn(III) to be responsible for the transition, stabilizing one monoclinic P2(1)/n variant over the other. The orbital reconstruction as a driving force for the transition is confirmed by analogous calculations of isostructural 3d(0) Na3ScF6, which shows no evidence of an IPT up to 6.82 GPa.

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Collaboration types
Domestic collaboration
Web of Science research areas
Materials Science, Multidisciplinary
Physics, Applied
Physics, Condensed Matter
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