Using the M 4(M=Ru, Rh, Pd) clusters as models, chemisorption of CO at the top and bridge sites has been performed by Gaussian programs, at the DFT/LANL1DZ level. Metal CO bonding and the influence of CO bond after ch...Using the M 4(M=Ru, Rh, Pd) clusters as models, chemisorption of CO at the top and bridge sites has been performed by Gaussian programs, at the DFT/LANL1DZ level. Metal CO bonding and the influence of CO bond after chemisorption CO have been studied, and the effects on the products of CO hydrogenation have been inferred. The calculations have shown that all the CO bonds are wakened after adsorption. Ru catalyst weakens C-O bond the most largely, Pd weakens C-O bond the least, and Rh lies between them. So it could be concluded that the products of CO hydrogenation have a trend to the hydrocarbons over the Ru catalyst, and the products are inclined to oxygenate over Pd, while there isnt obvious trend to the hydrocarbons and oxygenate on Rh.展开更多
On the basis of density functional theory and electronegativity equalization princi-ple, a new scheme has been developed for determination of atomic charges and bond charges in large molecules. In the new scheme, the ...On the basis of density functional theory and electronegativity equalization princi-ple, a new scheme has been developed for determination of atomic charges and bond charges in large molecules. In the new scheme, the molecular electron density ρmol(r) is partitioned as where ρα(r) and ρα-β(r) are the electron densities located on the atom α and bond α-β, respectively. The parameters A, B, C and D are the valence-state electronegativity and valence-state hardness. They are obtained by calibrating through model molecule calculations and are transferable and consistently usable for calculating the charge distributions in large molecules. The new scheme is tested through determination of atomic charges and bond charges in several large molecules. It has been shown that the re-sults of atomic charges and bond charges obtained by the new scheme dovetail those obtained by ab initio method very well. In addition, the new scheme presented here has the advantage of simplicity, rapidness and easy perform as well, so that it provides an efficient and practi-cal method for calculation of the charge distribution for a macromolecular system.展开更多
文摘Using the M 4(M=Ru, Rh, Pd) clusters as models, chemisorption of CO at the top and bridge sites has been performed by Gaussian programs, at the DFT/LANL1DZ level. Metal CO bonding and the influence of CO bond after chemisorption CO have been studied, and the effects on the products of CO hydrogenation have been inferred. The calculations have shown that all the CO bonds are wakened after adsorption. Ru catalyst weakens C-O bond the most largely, Pd weakens C-O bond the least, and Rh lies between them. So it could be concluded that the products of CO hydrogenation have a trend to the hydrocarbons over the Ru catalyst, and the products are inclined to oxygenate over Pd, while there isnt obvious trend to the hydrocarbons and oxygenate on Rh.
文摘On the basis of density functional theory and electronegativity equalization princi-ple, a new scheme has been developed for determination of atomic charges and bond charges in large molecules. In the new scheme, the molecular electron density ρmol(r) is partitioned as where ρα(r) and ρα-β(r) are the electron densities located on the atom α and bond α-β, respectively. The parameters A, B, C and D are the valence-state electronegativity and valence-state hardness. They are obtained by calibrating through model molecule calculations and are transferable and consistently usable for calculating the charge distributions in large molecules. The new scheme is tested through determination of atomic charges and bond charges in several large molecules. It has been shown that the re-sults of atomic charges and bond charges obtained by the new scheme dovetail those obtained by ab initio method very well. In addition, the new scheme presented here has the advantage of simplicity, rapidness and easy perform as well, so that it provides an efficient and practi-cal method for calculation of the charge distribution for a macromolecular system.
