Structural Stability Of Lithium Carbon Doped Clusters And The First Principle Of Eu / N Co - Doped Ti02 Optical Properties

Nano clusters as an intermediate state of microscopic particles and condensed matter, studying on its structure and nature helps understanding that of microscopic particles and the structure and properties of condensed matte. And it was applied in surface science, materials science, andeVen in nuclear physics, astrophysics. The study of stability of structure and properties of clusters become theoretical basis in developing new materials. Alkali metal lithium cluster and doping clusters are becoming a focus for sciestists because its wide application in combustion, catalytic, crystal growth and nucleation, coagulation and phase transformation, optical, etc. espcically for its structural stability and optical properties.Based on the first principles density functional theory, using GAUSSIAN packages, we taking the electron correlation energy and exchange energy into account, using B3LYP method and 6-31 g (d) basis set, making simulation calculation for the alkali metal lithium clusters Lin+/0/- (n=2-10) and non-metallic carbon doped lithium clusters LinC+/0/- (n=1-8) system.The ground state structure, stability, and electronic properties and vibration spectrum properties were analyzed. We also made Eu/N doping TiO2 photocatalysis on the optical properties using Vasp package. The main results are shown as follows:(1) The ground state structure, electronic properties and vibration spectrum of Lin+/0/-clusters are changed with the increase of the number of Li atoms. For the ground state structure, we can get Lin+/0/- by adding a lithium atom to Lin-i+/0/- when n< 6, the ground state structure of Lin+/0- become more dense with the increasing of the number of Li.The dissociation energy and second-order energy dispersion of Lin+/0/- shows Li2, Li4, Li8, Li3+ clusters has good stability. The vibration frenqency shows that the vibration spectrum located near to fingerprint area. It is magic that the difference between the maximum vibration frequency and the minimum vibration frequency of the ground state structure shows odd-even oscillation except for Li9. The Lin- vibration spectrum was deviated from the fingerprint area.(2) The ground state structures, electronic properties and vibration spectrum of LinC+/0/-clusters are changed with the increase of the number of Li atoms. For the ground state structure, LinC+/0/- clusters has the high symmetry and low electronic state except Li2C+ and Li6C-, but the symmetry of LinC+/- clusters is lower than that of LinC. The first three-dimensional structure of LinC is Li4C while that of LinC+/- is Li3C+/-. The second order dispersion and the HOMO-LUMO (Egap) of LinC+/0/- clusters show odd-even oscillation. And n-even number of clusters is more stable than the adjacent n-odd number clusters except LisC+/-. The vibration frequency shows the vibration spectrum all located in the fingerprint area. It is Strange that the ground state of the structure of the frequency difference is the smallest when the lithium atoms iseVen, on the contrary when the number of lithium atom is odd number, the structure of the ground state of the frequency difference is the biggest of all.(3)We calculated the electronic structure and optical properties of Eu/N doping TiO2 system using the plane wave pseudopptetial approach accouting spin polarization. The Eu/N doping is easier than single Eu or N doped TiO2 crystals, and the Ti atom is replaced by Eu and N atom. The forbidden band width gets narrow by Eu/N doping anatase TiO2. This leads to margin of absorption spectrum redshift, ventually enhanced photocatalytic activity. The Eu doped TiO2 system doesn’t enhance its capability of light absorption. N doped TiO2 makes visible light absorption ability enhancement. The Eu/N doping TiO2 system makes the absorption ability of visible light and the visible light catalytic activity enhanced.