First-Principles Study Of Several One-dimensional Materials

In this thesis we investigated several one dimensional materials based on density functional theory.Nanoscale magnetic devices have attracted much attention due to their po-tential applications in high-density information storage and quantum computing[25]. Using advanced techniques such as scanning tunneling microscope and me-chanically controllable break junction method, atom-size contacts and nanowires can be easily fabricated. Density Functional Theory is a very useful theoretical method to study this kind of materials.First we gived a short introduction to the development and the basic con-cept of density functional theory. Only simple H atom can be calculated by quantum mechanics at the very beginning of its foundation, several years later E. A. Hylleraas and D. R. Hartree calculated the ground state of Helium atom by variational and self-consistent field method, respectively; V. Fork improved the self-consistent field method forming the wellknow Hartree-Fork method, this method is the prototypes of many modern methods for electronic structure calculation; The density functional theory was founded in 1960', it is widely used in materials simulation and computational chemistry because of its high precision and moderate computational consume.In the third chapter we made a series of investigation to the one-dimensional borazine-vanadium nanowire, finding it could be a good spin filter. First of all, we constructed a sandwich-like nanowire built up with borazine molecu-lars and vanadium atoms; We find energy favoritable configuration by geom-etry relaxation. Then we calculated the band structure, density of states of the borazine-vanadium nanowire with geometry we got in the first step find-ing that the nanowire is ferromagnetic and half metel. Finally, we calculated the complex band structure of the nanowire; we predicted that when a finite length borazine-vanadium nanowire could also be a good spin-filter when they are placed between two electrode.In the forth chapter we ininvestigated several nanowires constituted with transition metal element absored on several zigzag graphene nanoribbons(ZGNRs). It is found that V, Ti chain prefer aborbed on the edge of the graphene nanorib-bons, with a line structure when absorbed on ZGNRs. The ZGNRs-Ti system is a ferromagnetism metal; the ZGNRs-V system is antiferromagnetism metal. When N=8,10, the C atoms near the V atoms prefer to deflex, when N=12,14, these C atoms prefer to upsweep, but when N=16,18, these C atoms bend just like the circumstances when N=8,10.In the final chapter we made a conclusion for this thesis, and made a plan for the following work.