Magnetism And Electronic Structure Of Transition Metal-Polyene Ring Sandwich Molecular Wires (SMWs)

Organic transition metal compounds is an important molecular spintronics materials with great potential application value, which are very significant in spintronic and spin-electronic devices.In this thesis, first-principle calculations have been performed to study the stability of geometry, electronic structure and magnetic properties of Polyenes ring(CnHn, n = 5,6,7,8 )-transition metal (Mt, Mt = Sc ~ Zn) sandwich molecular wires (SMWs). Our calculations used Dmol3 package of Materials Studio 4.3 software, which was based on the density functional theory (DFT).By geometry optimization, we find that when n = 5 or 6, almost all of the CnHn-Mt (Sc ~ Zn) structure of the sandwich molecular wires(SMWs) are stable (except C6H6Cu, C6H6Zn), which all atoms of the ligand carbon ring are in one plane and have no metastability structure.While when n = 7 (n = 8), only very few numbers of transition metal SMWs such as C7H7Sc, C7H7Ti, C7H7V, C7H7Co (C8H8Sc, C8H8Ti, C8H8V, C8H8Cr) , would have stably structure that all atoms of carbon ring remain in one plane. And with the increasing of the transition metal atomic number, (a) the structure of the Polyenes ring- transition metal SMWs become more and more unstable (absolute value of Eb became smaller and smaller); (b)the lattice constant c of the stable polyenes ring- transition metal SMWs decreases at first and then increases.Next, we study the electronic structure and magnetic properties of the stably Polyenes ring- transition metal SMWs, and discover that C6H6V, C6H6Mn, C5H5V, C5H5Cr, C5H5Fe SMWs have a half-metallic band structure, which are agreed with the calculation results by Lei Shen et al. Meanwhile, it unveils for the first time that C8H8V SMWs is a half- metallic materials, which the spin-up channel (two-electron) is metallic and spin-down channel (one-electron) is semiconducting.Then we analysis the density of states and partial density of states of C8H8V SMWs, which imply the half-metallic behavior mainly contributes by V 3d orbital and the C8H8 ring 2p orbital.To further verify the sources of the half-metal behavior, we also calculate the total spin magnetic moments of the C6H6V, C6H6Mn, C5H5V, C5H5Cr, C5H5Fe, C8H8V SMWs. The results show that the total spin magnetic moments of SMWs are an integer value, except that of C5H5Cr is 0.71μB.We analysis band structure and magnetic properties of valence electron configurations for polyenes ring- transition metal SMWs are consistent with the Dmol3's calculation results.