First-principles study of an S = 1 quasi one-dimensional quantum molecular magnetic material

We use density functional theory to study the structural, magnetic, and electronic structures of the organometallic quantum magnet ${\mathrm{NiCl}}_{2}\text{\ensuremath{-}}4\mathrm{SC}{({\mathrm{NH}}_{2})}_{2}$ (DTN). Recent work has demonstrated the quasi one-dimensional nature of the molecular crystal and studied its quantum phase transitions at low temperatures. The system includes a magnetoelectric (ME) coupling and, when doped with Br, the presence of an exotic Bose-glass state. Using the generalized gradient approximation with inclusion of a van der Waals term to account for weak intermolecular forces and by introducing a Hubbard $U$ term to the total energy, we systematically show that our calculations reproduce the magnetic anisotropy, the intermolecular exchange coupling strength, and the magnetoelectric effect in DTN, which have been observed in previous experiments. Further analysis of the electronic structure gives insight into the underlying magnetic interactions, including what mechanisms may be causing the ME effect. Using this computationally efficient model, we predict what effect applying an electric field might have on the magnetic properties of this quantum magnet.