Theoretical Investigations On Structures And Properties Of B-H And B-Au Binary Clusters

Clusters belong to a new generation of physical state falling in between micro atom, molecule and macro aggregated materials. Its special physical and chemical characteristics open up a new way for novel materials research. Now, it has been the main investigation direction that make use of means of theory to predict and research the structures and properties of new clusters for theoretical and experimental chemists. Based on density functional theory and wave function theory and H/Au/BO isolobal analogy, a systemic theoretical investigation on their structures and properties of B-H, B-O and B-Au clusters has been performed in this thesis. Simultaneously, the adiabatic and vertical detachment energies of the concerned anions have been calculated to predict their photoelectron spectrum. The concrete contents are presented as the followings:1. A systematic density functional theory and wave function theory investigation performed in this thesis reveals a planar-to-icosahedral structural transition between n=3-5in the partially hydrogenated B12Hn0/-clusters (n=1-6) upon hydrogenation of B120/-.Coupled cluster calculations with triple excitations (CCSD(T)) indicate that a distorted icosahedral B12H6cluster with C2symmetry is overwhelmingly favored (by35kcal/mol) over the recently proposed perfectly planar borozene D3h B12H6which proves to be a high-lying local minimum. So it is impossible to be synthesized in experiment. Instead, icosahedral B12cages at the centers of the B12Hn0/-clusters (n≥5) may serve as the most possible building blocks of novel boron-based nanomaterials. A similar2D-3D structural transition occurs to the corresponding boron boronyl analogues of Bi2(BO)n with n-BO terminals. Detailed adaptive natural density partitioning (AdNDP) analyses reveal the bonding patterns of these quasi-planar or cage-like clusters which are characterized with delocalized σ and π molecular orbitals. The electron detachment energies of the concerned anions and excitation energies of the neutrals are also predicted to facilitate their future experimental characterizations.2. DFT calculations at the B3LYP level show that B12(BO)-and B12Au--clusters possess similar C1(1A) ground states, which are based on the quasiplanar B]2cluster terminated with a BO unit and Au, respectively. The Bi2(BO)-and B12Au-clusters are thus valent isoelectronic because both BO and Au can be viewed as monovalent units, forming highly covalent B-BO and B-Au bonds analogous to the B-H bond in B12H-. Our results highlights not only the robustness of the B≡O boronyl group in boron-rich boron oxide clusters but also the Au/BO/H analogy in B-Au, B-BO and B-H complexes. Besides, at the B3LYP and CCSD(T) level, the the adiabatic and vertical detachment energies of the concerned anions have been calculated to predict the corresponding photoelectron spectra which also appear to be similar. To be emphasize, the theoretical PES of B12(BO)-and B12Au-have well agreement with their experimental PES which made by LS Wang Group, respectively.3. Boron could be the next element after carbon capable of forming2D-materials similar to graphene. Theoretical calculations predict that the most stable planar all-boron graphene is the so-called a-sheet. Detailed adaptive natural density partitioning (AdNDP) analyses unravel the bonding patterns of the π aromatic D3h B18H3-, D2h B18H4, C2v B18H5+and D6h B18H62+which are the building blocks of all boron a-sheet. Thus, a chemical bonding analysis for a-sheet has been performed and every filled hexagon we found three3c-2e a-bonds which are bordering upon the holes, three4c-2e σ-bonds at the junction of two filled hexagons, one7c-2e π-bond at filled hexagon and one6c-2e π-bond at empty hexagon. Our results show that σ-sheet possesses a and π doubly isoland aromatic and the mysterious structure with peculiar distribution of filled and empty hexagons can be rationalized in terms of chemical bonding by revealing the hexagon holes in a-sheet serve as scavengers of extra electrons from the filled hexagons. It is interesting to notice that, unlike graphene, the all-boron graphene a-sheet studied in this work possesses no localized2c-2e B-B σ-interactions, but all delocalized a electrons in its3c-2e and4c-2e bonds. The unprecedented chemical bonding model not only widens our understanding of chemical bonding in general, but also the presented bonding picture could be an advance toward rational design of future all-boron nanomaterials.