First principles calculations to investigate magnetic tetranuclear ferrous complexes

Spin-crossover has been intensively studied during the last past years due to the need to improve our understanding of the phenomenon and in the hope to exploit switching for data storage at the molecular level. Here we employ periodic spin polarized density functional theory in conjunction with the projector augmented wave method within the generalized gradient approximation, including a Hubbard interaction U at the iron site and a van der Waals correction, to investigate the structural, electronic and magnetic properties of the tetranuclear [Fe4(C23N6H15)4](BF4)4 molecular crystals. Two geometrical structures of the considered system are evidenced that correspond to two spin state configurations: HS-LS-HS-HS and HS-HS-HS-HS. We found that the two magnetic configurations seen experimentally can indeed by reproduced by our calculations, and that the magnetic centers are coupled ferromagnetically. These findings enable promising electronic and spintronic perspectives.