Density functional studies of molecular magnets

Abstract

After a general introduction into the field of molecular magnets the discussion focuses on a more specific description of their most important representative species, single-molecule magnets incorporating transition metal ions. We overview traditional model approaches for the phenomenological description of such systems and outline some ways used to parameterize the corresponding models from experiment and from first-principle calculations. The latter can be either multi-determinantal quantum chemical schemes or those based on the density functional theory. In particular we discuss Heisenberg exchange parameters and magnetic anisotropy constants. As a practical example, an introduction into problems and proper-ties of some single-molecule magnets which gained much attention within last years, namely Mn-12-acetate, ``Fe-8'' and ``V-15'' systems, is given. This introduction into systems is followed by a critical comparison of calculation schemes based on the density functional theory that are particularly well suited for the study of molecular magnets. For the above systems we select some benchmark results, obtained by different methods. Finally, we outline our recent progress in the study of other single-molecule magnets, including six-membered ``ferric wheels'', ``ferric stars'' and ``Ni-4'' molecules, which we studied with the use of first-principles methods SIESTA and NRLMOL. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.