A first-principles study on monoclinic $C2/c$ copper pyrovanadate $\beta {\text{-Cu}}_2{\text{V}}_2{\text{O}}_7$ has been performed using the generalized gradient approximation (GGA) and $\text{GGA}+U$ method. The optimized unit-cell parameters and atomic coordinates of $\beta {\text{-Cu}}_2{\text{V}}_2{\text{O}}_7$ agree well with experimental data. The optimized crystal structure of $\beta {\text{-Cu}}_2{\text{V}}_2{\text{O}}_7$ 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 $\beta {\text{-Cu}}_2{\text{V}}_2{\text{O}}_7$ is a semiconducting antiferromagnetic material with an indirect band gap and local magnetic moment per Cu atom of $0.73{\mu }_B$. 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 $\text{V}3d$, $\text{O}2p$, and $\text{Cu}3d$ electrons while the bottom of the conduction band is primarily composed of $\text{Cu}3d$ 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 $\text{V}3d$ and $\text{O}2p$ atomic orbitals and of $\text{Cu}3d$ and $\text{O}2p$, respectively.

• Received 4 September 2008

DOI:https://doi.org/10.1103/PhysRevB.79.125201