Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 31: Bio- and Molecular Magnetism
MA 31.2: Vortrag
Freitag, 30. März 2007, 11:15–11:30, H10
A first-principles DFT study of magnetic exchange paths in a BH4−-bridged dinickel(II) complex — •Claudia Loose — TU-Bergakademie Freiberg, Institut for Theoretical Physics, Leipziger Str. 23, 09599 Freiberg, Germany
We studied the BH4−-bridged dinickel(II) complex [(L)Ni2BH4]+, with L the dinucleating hexaaza-dithiophenolate ligand by first-principles DFT as implemented in the all-electron NRLMOL code. Our calculations find in agreement with experiment a ferromagnetic coupling between the two Ni-atoms resulting in an S=2 magnetic ground state of the complex. It is shown that exchange through the bridging BH4− contributes 2/3 of the total ferromagnetic exchange. This exchange proceeds through the p-states of BH4− which are energetically well aligned with the d-states of the magnetic ions. The remaining ferromagnetic exchange is partly derived from crossed interactions mediated by sulfur atoms from the ligand and partly by direct interaction of the two Ni2+-ions. Replacing BH4− by halides increases the ferromagnetic coupling. On the other hand in case of isoelectronic CH4 or noble gases the magnetic exchange path vanishes completely which supports the importance of the energetic position of the p-states. This opens the possibility to control the magnetic coupling by these p-states. Further, we predict that this complex will have a negative zero field splitting parameter D, so that it should eventually behave like a single molecule magnet. We would like to thank Prof. Kersting for providing the crystal data of the complex used in our studies.