Insulator to metal transition by bandwidth reduction

In a classic Mott system, the transition from the insulating to the metallic state occurs when the lattice spacing is reduced such that the increase in bandwidth W overcomes the local Coulomb repulsion U . In this picture, both W and the ratio W / U become larger with decreasing the distance between correlated sites. Here we show that, in transition-metal compounds, there is another path to metallization. It is associated with an expansion (instead of a compression) of the lattice and thus with a in W . In this scenario W / U grows with increasing distance—the opposite of the classical Mott case. Such a surprising inversion can be obtained by decoupling the main factors controlling W and screening. This mechanism explains the electronic behavior of the t 2 g 2 triangular lattice series LiV X 2 ( X = O , S, and Se) with increasing anionic size.