Nonlocal Coulomb Interaction in Mixed-Valence Material LiCu₂O₂

The nonlocal Coulomb interaction is known to play a key role in electronic instabilities, such as charge ordering or superconductivity. In this study, we extend its significance to mixed-valence systems by investigating LiCu₂O₂, where the mixed valency arises intrinsically from its own crystal structures. Using ab initio approaches incorporating extended Hubbard interactions, we successfully reproduce the unprecedented bandwidth enhancement observed in LiCu₂O₂ with respect to the conventional density functional theory prediction. Our comprehensive study, employing various levels of Hubbard corrections, highlights the decisive role of intersite Coulomb interaction in governing Cu d-ligand p hybridization and the resulting electronic structure. This work not only elucidates the fundamental impact of intersite Coulomb interactions in mixed-valence materials but also establishes a reliable framework for their accurate theoretical description.