JETP Letters: issues online

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 t_2g 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 t_2g 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 low-temperature magnetic properties of V₆O₁₃ involve the spin-Peierls transition assisted by orbital ordering and concomitant distortions of the crystal structure.