Chains of magnetic ions in NH$_4^+$-intercalated vanadium pentoxide

We explore the electronic and magnetic properties of NH$_4^+$-intercalated vanadium pentoxide (NH$_4^+$-V$_2$O$_5$), a material that has been identified as a promising cathode for aqueous zinc-ion batteries. Density Functional Theory (DFT) calculations incorporating the Hubbard U correction reveal that NH$_4^+$-V$_2$O$_5$ is an antiferromagnetic insulator with an energy gap of 1.97 eV. The introduction of NH$_4^+$ ions into the V$_2$O$_5$ structure results in significant structural distortions, leading to the formation of magnetic vanadium ions (V$^{4+}$, $3d^1$) and non-magnetic ions (V$^{5+}$, $3d^0$). The magnetic vanadium ions are organized into chains with antiferromagnetic order along the $a$-axis. Our findings indicate that NH$_4^+$-V$_2$O$_5$ exhibits strong electron correlation effects and negligible interchain magnetic interactions, rendering it a promising candidate for a one-dimensional magnetic van der Waals system. This work provides insights into the electronic and magnetic behaviors of NH$_4^+$-V$_2$O$_5$, with implications for its potential applications in energy storage technologies.