Electronic structure and magnetic anisotropy of the   [Co_4(hmp)_4(CH_3OH)_4Cl_4] molecule
  Accurate density-functional based calculations have been performed on the Co_4(hmp)_4(CH_3OH)_4Cl_4 molecular magnet where hmp is deprotonated hydroxymethyl pyridine. In addition to the experimentally observed staggered geometry, we identify two isomers, referred to as eclipsed and half-staggered/half-eclipsed, that are reasonably low in energy. Our calculations show that the magnetic anisotropy is strongly dependent on the pyridine-pyridine separation and that the three structures exhibit easy axis, easy plane and triaxial behavior. Other effects such as partial reprotonation of the hmp is considered. 
Tunna Baruah (1,2), Mark R. Pederson (2) ((1)Georgetown University (2)   Naval Research Laboratory)