Papers by Keyword: PDOS

Abstract: Electronic structures and optical anisotropy of α- and β-phase copper phthalocyanine (CuPc) molecular crystals have been systemically investigated by first-principles calculations based on Density Functional Theory (DFT). Both crystals were shown to be small gap organic semiconductors with relatively flat and dispersionless bands. The α-CuPc was a direct band gap semiconductor, whereas the β-CuPc was an indirect band gap semiconductor. The analysis of Partial Density of States (PDOS) showed that the top of valance band was mainly contributed by N 2p and C 2p states; the bottom of the conduction band was mainly contributed by N 2p, C 2p and Cu 3d states. The interband optical properties, such as the complex dielectric function, absorption coefficient and complex refractive index, showed a high degree of anisotropy that can be traced to the unique structures of these molecular crystals. The calculated dielectric function for α-CuPc in the low energy region was consistent with the experiment results proposed in the literature. These calculations provided particular interpretations on electronic structure and optical properties of α- and β-CuPc organic semiconductors that were critical to optoelectronics, which would promote the applications of these materials in semiconductor optoelectronic devices.

Abstract: Density-functional theory (DFT) theory is conducted for the structural and electronic features at the Hg/Al₂O₃ interface by the analysis of optimal structural geometry, partial density of states (PDOS) and difference charge density. The two adsorption sites of on-top and hollow locations according to the symmetry is adopted to construct the associated interfacial models between Hg atom and free surface. The calculated studies show that the oxygen atoms near Hg atom in the Al₂O₃ surface, for both on-top and hollow sites, have the gathering effect by shifting toward Hg atom. But their interacting electrons at the interface exhibit different statues in terms of the PDOS analysis that there have no evolution tendency to form the bond between associated O and Hg atoms at the on-top site; and the occurrence of Hg-5d and O-2p overlapping orbitals reveals the strong covalent bond existed at the interface. The PDOS curves show that Al atom in the surface is not liable to contribute to the formation of corresponding bonds by mixing its electrons with Hg atom. Meanwhile, the calculated results derived from difference charge density are in good agreement with the PDOS analysis. The calculated results support some advanced atomic investigation on design a new sorbent refined from fly gas, especially improving the mercury removal from the flue gas.

Abstract: The organic-inorganic hybrid compounds have attracted much attention for their interesting structures and various properties. In present work, we concentrated on the band structures of the hybrid compound (C4H9NH3)2GeI4 and tried to find out the relations between the geometry structure and the properties. The hybrid’s primitive cell was large and including too many atoms, so it was difficult to have a direct and clear analysis on the band structure. The hybrids’ DOS and PDOS were analyzed instead, as it was another effective way to analyze the band structure of the hybrid especially when the band structure was complicated. The model of (C4H9NH3)2GeI4 was set up, and the program based on the first principle had been employed to calculate its band structure. The difference of iodine’s PDOS caused by structure was also discussed.