Organic Metal Sandwich Structure Of Clusters And The Study Of The Theory Of The Electromagnetic Properties

Low-dimensional nanomaterials have attracted people’s extensive attention due to their large surface area/volume ratio and quantum-size effect. The size-dependent physical and chemical properties make them potential candidates in the application of photoelectronic device, magnetic storage media and efficient catalysts, et al. The dissertation is dedicated to the study of organic-transition metallic sandwich clusters and their infinite one-dimension nanowires by means of first-principles calculations. The purpose of this dissertation is to investigate their growth mechanism and bonding characters, explore the physical and chemical foundation of their stabilities and electronic/magnetic properties, as well as their transport properties and negative differential resistance. The main results are listed below:We systematically investigate the structural, electronic and magnetic properties of one-dimensional bimetallic naphthalene sandwich nanowires,[Np2V2TM2]∞(TM=Ti, Cr, Mn, Fe, Np=C10H8, naphthalene) by employing ab initio calculations. Three structures with different alignments of TM atoms (isomer-Ⅰ,Ⅱ,Ⅲ) are considered and they are all of high stability with exceptions of [Np2V2Mn2]∞(isomer-Ⅱ,Ⅲ) and [Np2V2Fe2]∞(isomer-Ⅲ). Furthermore, the electronic and magnetic properties of [Np2V2TM2]a, show clear dependence on chemical component and geometries. Most sandwich wires favor ferromagnetic coupling while [Np2V2Ti2]∞(isomer-Ⅰ,Ⅲ) shows antiferromagnetic ground states. Interestingly,[Np2V2Cr2]∞(isomer-Ⅱ,Ⅲ),[Np2V2Mn2]∞(isomer-Ⅰ) and [Np2V2Fe2]∞(isomer-Ⅰ) are found to be robust ferromagnetic half-metals, and [Np2V2Cr2]∞(isomer-Ⅰ) is ferromagnetic quasi-half metal.We systematically investigate the cyclooctatetraene ligand sandwich clusters, TMnCOTn+1(TM=Ti, Zr, Hf; COT=cyclooctatetraene, n=l~3) by means of density functional calculations. The HOMO-LUMO gap of these clusters show "odd-even" tendency towards the cluster size, of which, TM2COT3has the largest kinetic stability for its largest HOMO-LUMO Gap. The binding energies of all the clusters are over4.284eV, showing that they possess large thermaldynatic stability. Among all the clusters, TMCOT2has the largest binding energy. Moreover, most clusters are nonmagnetic with zero magnetic moment with one exception of TiCOT, which is ferromagnetic having a magnetic moment of2μb. Most interestingly, the spin stability of TinCOTn+1is far larger than that of EunCOTn+1mentioned previously.We systematically investigate the spin transport behaviors of (BzVBzTM)n(TM=Cr, Fe, Mn)using DFT and nonequilibrium Green’s function techniques. Our results show that all the clusters display good spin polarization near the Fermi level when coupled Au electrodes. Moreover, analysis of I-V curves indicate that most clusters, BzVBzCr、 BzVBzFe、 BzVBzFeBzV、BzVBzFeBzVBz、BzVBzMn、BzVBzMnBzV and BzVBzMnBzVBz, have negative differential resistance (NDR).