Describing the spin-polarized transport in molecular junctions by ab-initio calculations

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Applying ab initio density functional theory we will study structural properties of simple organic molecules between metallic leads. Combining density functional theory with the nonequilibrium Green function approach we will investigate the spin-dependent transport properties in these systems. Our molecular system of choice will be the metal-benzene multipledecker sandwiches Xn(C6H6)m with paramagnetic transition-metal centers, X=V,Nb,Ta, as well as their functionalized derivatives, attached to Cu(111) leads. The transition-metal ion X in these molecules induces a magnetic moment and the spin-dependent conductance through the molecules will be studied as function of the ordering of these moments (ferromagnetic, antiferromagnetic, noncollinear), and of relative orientation of these moments with respect to the molecule leading to a ballistic anomalous magnetoresistance due to the effect of the spin-orbit interaction. Ferromagnetic CoCu(111) leads are explored as spin-injectors. Charging of the molecules as a function of the details of the absorption and the applied bias will be investigated including effects of the self-interaction correction beyond usual density functional theory methods.To achieve these goal the ab initio methods are developed in various directions including the implementation of an all-electron transport scheme for one-dimensional molecular structures attached to semi-infinite surfaces and a suitable scheme for the self-interaction correction.