Electronic transport of a two-probe system consisting of Au (111) electrodes and two base pairs sandwiched between Au (111) contacts is investigated with density functional theory combined with non-equilibrium Green's function method.It shows that conductance of base pairs is sensitive to distance between electrodes and oscillates.At a fixed gap between electrodes,transverse transport of base pairs under low bias is calculated and is compared with base pairs with a silver ion.It shows that conductive capability of G-C decreases and that of A-T increases as silver ions are combined with base pairs.

Electronic structure and magnetism of Fe_n/Cr_n superlattices(SL) with various layer thickness(n=1,3,5) are studied using a full-potential linearized augmented plan-wave(FLAPW) method within a density functional formalism. It is shown that ferromagnetic state is a preferable phase in the ground state and the intrinsic spin density wave length is about 2 monolayers(ML). The magnetic moment of Fe layer is slightly modified by an intelvening Cr layer, and becomes stronger with the increase of n. The direction of Cr magnetic moment alternates layer by layer. An antiferromagnetic coupling hetween interfacial Fe and Cr layers is observed. There is a moderate hybridization between d-states of Fe and Cr atoms near Fermi energy.