Charge-orbital Ordering, Magnetic State, and Exchange Couplings in Quasi-One-Dimensional Vanadate V6O13

Abstract

Charge and orbital ordering, magnetic state, and exchange couplings in quasi-one-dimensional vanadate V6O13, a potential cathod material for Li-ion batteries, are investigated using the density functional theory with Coulomb interaction correction method (DFT + U). While the difference between t2g orbital occupancies of V4+ (with a nominal 3d1 electronic configuration) and V5+ ions is large and gives direct evidence for charge and orbital ordering, the screening is so effective that the total 3d charge disproportionation is rather small. Our results show that the occupied t2g states of V4+ ions in the single V-V layer form a spin-singlet molecular orbital, while the rest half of V4+ ions in the structurally distinct double V-V layers order antiferromagnetically in the low-temperature insulating phase of V6O13. We conclude that the metal-insulator transition and lowtemperature magnetic properties of V6O13 involve the spin-Peierls transition assisted by orbital ordering and concomitant distortions of the crystal structure.

Structures, Phase Stability, Amorphization, and Decomposition of V6O13 at High Pressures and Temperatures: Synthesis of Rutile-Related V0.92O2

“…The vanadium oxides in the Wadsley homologous series V n O 2 n +1 between α-V 2 O 5 ( Pmmn , Z = 2) and VO 2 (B) ( C 2/ m , Z = 8) undergo a MIT accompanied by orbital ordering. − Their crystal structures could be derived from the structure of VO x ( Fm m , Z = 4), where x ≈ 1 . The mixed-valence oxide V 6 O 13 ( C 2/ m , Z = 2) is composed of single and double layers formed by edge- and corner-sharing distorted VO 6 octahedra .…”