Preliminary Research Of Calculation For Active Composite Oxide Electrode Materials

The calculations of active composite oxide electrode materials have not yet been found on relevant reports. The crystal structures and electronic structures of rutile SnO2 as well as Ru, Ir single-doped and co-doped SnO2 were studied by first-principles calculations based on the density functional theory (DFT) with VASP software package. The in-depth knowledge of the crystal structures and conduction mechanism of SnO2-based active composite oxide electrode material were obtained by first-principles calculation. Thus provide a theoretical basis for the preparation of electrode materials with excellent electrical properties.The optimized structure parameters of pure rutile SnO2 were calcutated based on supercell, the results agree well with data given in the literature within-0.04%. The density of states and the band structure of rutile SnO2 indicate that it is direct-gap semiconductor with Eg=1.1eV. The valence band (VB) near the Fermi-level is composed by O-2p and the conduction band (CB) is composed by Sn-5s and O-2p.The optimized structure parameters of Ru-doped rutile SnO2 were calcutated based on supercell. The plot of total energy vs. volume (E-V) was fitted using third-order Birch-Murnaghan equation of state. The calculated results are good agreement with the literature. The electronic structures calculations show that with the introducing of 4d electron orbital by doping Ru atoms, the impurity energy levels formed at the lowest position of the conduction band, which makes the conduction mechanism change greatly. With the increasing amount of Ru atoms doped in SnO2, the number of relative electrons into the conduction band increased gradually. The band gap first decreases and then increases and the electrons effective mass have the same changing tendence. And the carrier concentration, the electron mobility and the conductivity increases gradually.The optimized structure parameters of Ir-doped rutile SnO2 were also calcutated based on supercell. The lattice parameters change linearly with the concentration of Ir increased. The lattice parameters and total energy of Sn1-xIrxO2 are range from SnO2 to IrO2. Compared with the Ru-doped SnO2, the extent of the Fermi level into the conduction band is larger. With the amount of Ir atoms doped SnO2 increased, the number of relative electrons into the conduction band increased. And the carrier concentration, the electron mobility and the conductivity increases gradually.The lattice parameters and total-energy of rutile Sn1-2xRuxIrxO2 (Ru and Ir atoms co-doped) are between that of Sn1-xRuxO2 and Sn1-xIrxO2. With the concentration of Ru and Ir atoms increased, the number of relative electrons into the conduction band, the carrier concentration, the electron mobility and the conductivity increaseed gradually.The influences of doping atoms on the conductive properties of SnQ2 semiconductor materials were calculated. The doping element and its concentration were chose by comparing the results of the electronic structures when Ru and Ir atoms. Under the same doping percentage, the improvements of dopant atoms on the electric conductivity of SnO2 are in a descending order as:Ir atoms single-doped Sno2, Ru and Ir atoms co-doped SnO2 and Ru atoms single-doped Sno2. The results have important directive function for the preparation of electrode materials.