Mechanism of the metal-insulator transition of hollandite vanadate K2V8O16

We make the electronic structure calculations of hollandite vanadate K2V8O16 using the generalized gradient approximation (GGA) in the density functional theory, where the Hubbard-type repulsive interaction U is taken into account (GGA+U). We in particular calculate the electronic structure of the low-temperature phase of this material using the crystal structure reported by Komarek et al. We find that the electronic wave functions near the Fermi level are predominantly of the d(xy) character and form the quasi-one-dimensional energy bands. The energy bands are made of the single chains of the VO6 octahedra rather than the double chains. The effects of strong electron correlations play an essential role here. Based on these results, we discuss possible mechanisms of the observed metal-insulator transition of this material.