| Nanocluster is a unique mesoscope structure between micro and macro-scaled particles. With the quantum size effect of the clusters, some novel phenomena related with the geometrical, electrical, magnetic and optical properties appear. Silicon clusters have been investigated extensively in experimental and theoretical reports as a significant semi-conducter material. Since the pure silicon clusters are geometrically unstable, dopping appropriate transition metals (TM) not only can effectively stabilize the clusters, also improve the electronic properties of them. The previous researches mainly focused on free TM adulterating silicon clusters (TM@Sin). Considering the experimently specific condition (such as:the substrate), this paper have constructed a series of computational models of TM@Sin clusters supported on graphene and calculated them by density functional theory (DFT). Additionally, the properties of Irn and Tan(n=4-10.12,13) clusters are contrastively studied for their complementary d electrons.The third chapter mainly studied the geometrical and electrical properties of TaSin(n=1-3,12) supported on graphene by PAW density functional theory(DFT) in MedeA-VASP software package, including the structural stability, charge transfer property as well as difference charge density. It is showed that Ta atom prefers locating over the hollow site of graphene for TaSin(n=1-3) clusters with obvious shifts of the Ta-Si bonds and binding distances between the clusters and subetrate. However, TaSi12 only can be physically adsorbed above the top sits of grapheme with almost original structrue. It is rationalized when considering the interaction between Ta and C is gradually weakened with the increasing of Si atoms which surrounded the Ta. The interaction is comparatively strong between TaSin (n=1-3) and grapheme. While, Ta atom nearly interacts with C atom until Si atoms increases to 12 since Ta atom is capsulated in the center of 12 Si atoms. From the point of adsorption energy (Ea), the average Ea decreased with the nuber of silicon atoms increasing, leading to chemisorption between TaSin(n=1,2) and graphene and physisorption between TaSin(n=3,12) and grapheme.During the adsorption, charges transfer appears between transitional metal and grapheme, leading to a p or n doping in the electronic structure of grapheme. Graphene will be n doped for TaSin (n=1,2) adsorption, on the contrary, p doped for TaSin (n=3,12).The geometrical and electrical structures of Irn and Tan(n=4-10,12 and 13) clusters, both period 6 elements with complementary d electrons, are contrastively investigated by relativistic density functional method in the fourth chapter. The ground state structures of Irn favor non-compact structures growth pattern like prism or simple cubic, while Tan clusters are more supportive of compact structures. The average binding energies of Irn and Tan (n=4-10) clusters show size effect. The curve of Irn displays a little oscillates, while that of Tan ascends smoothly. The second-order difference of energy, the gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) and the atomic average magnetic moments for the lowest-energy Irn (n=4-10) geometries all show obvious odd-even alternative behaviors which is weak for Tan (n=4-10) clusters. And Irn clusters with even number are more stable than those with odd number, but it is converse for Tan. In addition, the gaps between HOMO and LUMO are generally smaller than 0.3 eV except Ta4, indicating a strong chemical activity. The atomic average magnetic moments for lrn(n=4-7) are far higher than those of Tan, while they are very close and comparatively low when n>8. |
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