Electronic structure and magnetic properties of monoclinicβ-Cu2V2O7: AGGA+Ustudy

Abstract

A first-principles study on monoclinic $C2/c$ copper pyrovanadate $\ensuremath{\beta}{\text{-Cu}}_{2}{\text{V}}_{2}{\text{O}}_{7}$ has been performed using the generalized gradient approximation (GGA) and $\text{GGA}+U$ method. The optimized unit-cell parameters and atomic coordinates of $\ensuremath{\beta}{\text{-Cu}}_{2}{\text{V}}_{2}{\text{O}}_{7}$ agree well with experimental data. The optimized crystal structure of $\ensuremath{\beta}{\text{-Cu}}_{2}{\text{V}}_{2}{\text{O}}_{7}$ indicates the existence of one-dimensional -Cu-Cu-Cu-Cu- chains. The electronic structure and magnetic properties were evaluated by the $\text{GGA}+U$ calculations, which indicate that the $\ensuremath{\beta}{\text{-Cu}}_{2}{\text{V}}_{2}{\text{O}}_{7}$ is a semiconducting antiferromagnetic material with an indirect band gap and local magnetic moment per Cu atom of $0.73{\ensuremath{\mu}}_{B}$. The intrachain exchanges for short and long Cu-Cu couples are estimated to be 6.4 and 4.1 meV, respectively, while the calculated interchain exchange (2.1 meV) is smaller, which indicate the one-dimensional character. The top of the valence band is composed of $\text{V}\text{ }3d$, $\text{O}\text{ }2p$, and $\text{Cu}\text{ }3d$ electrons while the bottom of the conduction band is primarily composed of $\text{Cu}\text{ }3d$ electrons. Valence electron-density distribution map indicates the V-O and Cu-O covalent bonds. Calculated partial electronic density of states strongly suggests that the V-O and Cu-O covalent bonds are mainly attributed to the overlaps of $\text{V}\text{ }3d$ and $\text{O}\text{ }2p$ atomic orbitals and of $\text{Cu}\text{ }3d$ and $\text{O}\text{ }2p$, respectively.