Microscopic origin of pressure-induced isosymmetric transitions in fluoromanganate cryolites

Nenian Charles*, James M. Rondinelli

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

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 eg manifold of the 3d4 Mn(III) to be responsible for the transition, stabilizing one monoclinic P21/n variant over the other. The orbital reconstruction as a driving force for the transition is confirmed by analogous calculations of isostructural 3d0 Na3ScF6, which shows no evidence of an IPT up to 6.82 GPa.

Original languageEnglish (US)
Article number094114
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume90
Issue number9
DOIs
StatePublished - Sep 24 2014

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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