Application Of Density Functional Theory

The density functional theory(DFT) as one of the most popular methodologies in theoretical chemistry has been widely used in different disciplines including Chemistry,Physics,Materials Science,and Biology.In the present study,DFT calculations were applied to the computational study on complexes of transition metals with extended-TTF dithiolate ligans,ethanol adsorption on the Pd(111) surface, and polydiacetylene and its derivates.The relevant results are summarized as follows:Ⅰ.DFT Study on Complexes of Transition Metals with Extended-TTF Dithiolate LigandsGeometries and properties of complexes of transition metals with extended-TTF dithiolate ligands were investigated by density functional calculations.The effects of metal replacement and ligand modification on the structures and properties of the complexes have been explored.The results indicate that the HOMO-LUMO gaps in these complexes are very small.The complexation of transition metals with the extended TTF dithiolate ligands as well as the oxidation of complex plays an important role in reducing the HOMO-LUMO gap.Ⅱ.The First Principle Study of Ethanol Adsorption on the Pd(111) SurfaceDFT calculations have been performed to explore the ethanol adsorption on Pd(111) surfaces.Relative energies,equilibrium geometries,vibrational frequencies, and electronic structures of monomer,dimer,and one-dimensional(1D) chain of ethanol molecules adsorbed at the surface were investigated and analyzed in details. Our calculations indicate that ethanol molecules prefer to adsorb at atop sites of the Pd(111) surface,and the adsorption is exothermic.Adsorbed ethanol molecules are likely to form dimer and chain through the hydrogen bond interactions.Our results also show that there are red shifts of v(O-H) frequencies for ethanol molecules adsorbed on the Pd(111) surface.Ⅲ.DFT Study on Polydiacetylene and its Derivates Optimized geometries and vibrational frequencies of polydiacetylene(PDA) and its derivates were studied by DFT calculations at the B3LYP/6-31G* level.The timedependent density functional theory(TD-DFT) was employed to calculate the vertical transition energies and oscillator strengths of such carbon chains.The results show that different side groups can significantly modify their structures and properties,but the substitution effect can be ignored when the terminal atoms of PDA were replaced by light atoms Li,Be,and B.The periodic boundary condition(PBC) calculations reveal that the strongest adsorption for the infinite chain of PDA appears at 723 nm, and the HOMO→LUMO transition is responsible for this strong electronic transition.