Structural instability and the Mott-Peierls transition in a half-metallic hollandite : K${}_2$Cr${}_8$O${}_{16}$

Abstract

In order to explore the driving mechanism of the concomitant metal-insulator and structural transitions in quasi-one-dimensional hollandite K${}_2$Cr${}_8$O${}_{16}$, electronic structures and phonon properties are investigated by employing the {\it ab initio} density functional theory (DFT) calculations. We have found that the imaginary phonon frequency reflecting the structural instability appears only in the DFT+$U$ ($U$: Coulomb correlation) calculation, which indicates that the Coulomb correlation plays an essential role in the structural transition. The lattice displacements of the softened phonon at X explain the observed lattice distortions in K${}_2$Cr${}_8$O${}_{16}$ perfectly well, suggesting the Peierls distortion vector {\bf Q} of X (0, 0, 1/2). The combined study of electronic and phonon properties reveals that half-metallic K${}_2$Cr${}_8$O${}_{16}$, upon cooling, undergoes the correlation-assisted Peierls transition to become a Mott-Peierls ferromagnetic insulator at low temperature.

References in corpus (4)

• Orbital-assisted metal-insulator transition in VO${}_2$
• K${}_2$Cr${}_8$O${}_{16}$ predicted as a half-metallic ferromagnet: Scenario for a metal-insulator transition
• Theoretical study of the electronic states of hollandite vanadate K${}_2$V${}_8$O${}_{16}$
• Double Exchange Ferromagnetism in the Peierls Insulator State

Cited by in corpus (1)

• Charge Localization and Ordering in A${}_2$Mn${}_8$O${}_{16}$ Hollandite Group Oxides: Impact of Density Functional Theory Approaches