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江元生, Xin Wang, Shuhua Li, * and Yuansheng Jiang
Inorganic Chemistry, Vol. 43, No.20, 2004,-0001,():
-1年11月30日
The mechanism of H2O2 dismutation catalyzed by the dibenzotetraaza[14]annulene-Fe(Ⅲ) complex ([Fe(C24H22N4O4)]+) which was recently reported (Paschke, J.; Kirsch, M.; Korth, H. G.; de Groot, H.; Sustmann, R. J. Am. Chem. Soc. 2001, 123, 11099) has been investigated by density functional theory using the B3LYP hybrid functional. The quartet potential energy profile of the catalytic reaction has been explored. In the whole catalytic cycle, the ratedetermining step is found to be the O-O bond homolytic cleavage, without the assistance of solvent molecules in the second coordination shell. The calculated free energy barrier for this step is 10.8kcal/mol, which is in reasonable agreement with the experimental facts. The calculations also show that the hydroxyl and hydroperoxyl radicals may be generated in the reaction processes, but they can be efficiently quenched in strongly exothermic steps. This study provides a satisfactory explanation to the observed efficiency of the H2O2 dismutation catalyzed by this complex.
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江元生, SHUHUA LI, JING MA, YUANSHENG JIANG
J Comput Chem 23: 237-244, 2002,-0001,():
-1年11月30日
A linear scaling local correlation approach is proposed for approximately solving the coupled cluster doubles (CCD) equations of large systems in a basis of orthogonal localized molecular orbitals (LMOs). By restricting double excitations from spatially close occupied LMOs into their associated virtual LMOs, the number of significant excitation amplitudes scales only linearly with molecular size in large molecules. Significant amplitudes are obtained to a very good approximation by solving the CCD equations of various subsystems, each of which is made up of a cluster associated with the orbital indices of a subset of significant amplitudes and the local environmental domain of the cluster. The combined effect of these two approximations leads to a linear scaling algorithm for large systems. By using typical thresholds, which are designed to target an energy accuracy, our numerical calculations for a wide range of molecules using the 6-31G or 6-31G* basis set demonstrate that the present local correlation approach recovers more than 98.5% of the conventional CCD correlation energy.
coupled cluster, local correlation, linear scaling, localized molecular orbital
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【期刊论文】Is Ferromagnetic Spin Coupling Constant within Homologous Di-and Triradicals?
江元生, Shuhua Li, Jing Ma, and Yuansheng Jiang*
J. Phys. Chem. 1996, 100, 4775-4780,-0001,():
-1年11月30日
By means of the powerful Lanczos algorithm, the nonempirical valence bond (VB) model has been applied to investigate the low-lying electronic states for three typical types of homologous
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江元生, Yong Pei, Jing Ma, * and Yuansheng Jiang
Langmuir 2003, 19, 7652-7661,-0001,():
-1年11月30日
Quantumchemistry and molecular mechanics calculations are performed to study formation mechanisms and packing structures of octadecanal and octadecene monolayers on Si(111). The radical chain mechanism is investigated by density functional theory with cluster models. Transition states of key steps involving abstracting a neighboring hydrogen atom from the surface are confirmed with the six-membered ring structures. Energy barriers for abstractions of the surface H to form new reactive surface Si radicals in the substitution of Si(111) via Si-O and Si-C linkages are 18.05 and 14.97 kcal/mol, respectively. Based on the radical chain mechanism, we investigate the linear and zigzag acking structures of alkoxyl chains on Si(111) with substitution percentages of 50%, 66.7%, and 75% using a series of two-dimensional repeating cells. By comparison of packing energies of octadecanoyl chains at different substitution percentages, 66.7% is predicted to be an optimal substitution ercentage, which agrees with experimental observations. At this surface substitution, packing structures of the monolayer such as tilt angles and film thickness are well correlated with experimental data. The difference in packing structures between monolayers on Si(111) via Si-Oand Si-C linkages is rationalized by their different van der Waals radii of surface linkage groups and tilt angles of chains.
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【期刊论文】Effective Valence Bond Model Study on Conjugated Hydrocarbons Containing Four-Membered Rings
江元生, Jing Ma, Shuhua Li, and Yuansheng Jiang*
J. Phys. Chem., Vol. 100, No.37, 1996 15069,-0001,():
-1年11月30日
By employing the Lanczos method, the effective valence bond model (EVB) is exactly solved for a series of conjugated hydrocarbons with four-membered rings. Several indices calculated from the EVB ground-state energies and wave functions are applied to interrelate with bond lengths, stabilities, and reactivities of these systems. Our results agree well with related experimental observations and deductions of molecular orbital theory. The failure of the classical valence bond theory in these systems is also exposed.
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