Theoretical Studies On The Clusters Of Spectra And Superatomic Characteristics

With the tremendous improvements in hardware and software of computer, com-putational chemistry has became very popularly, which is a discipline dealing with the systems and the modeling simulation by the computer. Density functional theory (DFT) is one of the commonly used methods since its computational consume is moderate, with high accuracy. Meanwhile, the size of clusters are between molecular species and solids, including unique properties for the controllable size and composition. One tries to find a stable new kind of cluster as a building block to form molecules and materials. Superatom is one of such clusters. In the dissertation, we first simulate the photoelec-tron spectrum of clusters, then, assemble molecules and bulk phase materials, finally, introduce the dissociation and diffusion of H2 on doped Al(111) surface.In chapter 1, We first briefly review the history of quantum chemistry calculation, and then focus on the concept and development of DFT. In the solid, the properties of ground state can be expressed as the functional form of ground state electronic density, which is the only variable. One of the main directions of DFT is to develop the appro-priate exchange-correlation function. Lastly, we introduce the software package used in the thesis.In chapter 2, the experimental photoelectron spectra of [Re6Q8L6]n-(n=2, Q=S, Se, Te, L=CN; n=3, L=CN, Q=S, Se, Te, L=Br, Q=S, L=I, Q=Se) are fitted combining with DFT. Start with the basic knowledge of photoelectron spectrum, including pho-toelectric effect, XPS spectrum, UPS spectrum, as well as two methods for theoretical analysis of photoelectron spectrum, sudden approximation and the adiabatic approxi-mation. Then, we analyze the electrons detachment of each system, individually. For the closed electronic levels, with more intensive spectra, which are not easy to spec-ify state to state, we have only specified the ADE and VDE value and compared with the experimental values. For higher binding energies excited, we predict the excited energies values in the frame of TDDFT.In chapter 3, we use the superatom core Au4 to mimic the feature of sp3 hybrid C atom, and confirm the universality of superatom composing molecules. Based on the jellium model, the effective electronic levels of superatom Au4 are 1S2 1P2, the same number of valence electrons to C atom,2s22p2. We demonstrate the similarities in terms of the molecular orbital (MO) contours and the chemical bond patterns of super-atomic molecules and corresponding simple molecules. In this chapter, we introduce the relevant background, including the basic characteristics of the cluster, the jellium model, the finding and concept of superatom, and the feature of superatoms mimicking Inert Gas Atoms, Halogens, Alkali and Multivalence character. For the superatomic molecules, we use the AdNDP tool and the super valence bond (SVB) model to ana-lyze the chemical bond patterns, molecular orbital (MO) based on MO theory. Also, we compare the energies, verify the stability of superatomic molecules.In chapter 4, the open shell superatom Au16 is used as a building block to assemble diamond-like structure Au128.It is well known that adjusting the size and composition of the clusters can control their properties, for example, physical, chemical, electronic, optical and magnetic properties, to tailor what we need. Among them, the stable clusters can assemble into the material as a basic building block, like atoms and molecules. First, we outlined the characteristics of cluster stack materials, some instances exist in nature, how to use cluster to assemble materials, and noted that the superatom is an ideal building blocks. Then, from the view of experimental and theoretical, we analyze the feasibility of Au16 as building block, as well as how to set up materials. Finally, describe our work.In appendix, the dissociation and diffusion of H2 on doped Al(111) surface is stud-ied by First-principles calculation. In the experiment, two activity sites are found in favour of H2 dissociation on the 2Ti@Al(111) surface. Then, we investigate the prop-erties of H2 on Al(111) surface doped by two Ti atoms.