用Xα-DV方法研究CO,NO在Ⅷ族过渡金属表面的化学吸附(Ⅰ)——CO吸附在Rh(111)面的电子结构

本文用自洽Hartree-Fock-Slater分子丛方法计算了CO在Rh(111)面上(θ≤1/3)的电子结构。计算了分子丛的总能量、基态能级随吸附高度的变化。从总能量曲线确定的最佳键长为1.85?与实验值1.95±0.1?符合得较好。相应的吸附能为0.98eV比实验值1.3eV略小。在以上最佳键长处计算了总态密度,考虑终态和弛豫效应后与UPS实验结果符合更好。通过CO分子接近表面时各分子轨道能量本征值的变化,讨论了各轨道的成键、反键特征。通过Mulliken总数分析和用CO分子波函数展开总波函数的系数分析着重讨论了CO分子被过渡金属Rh吸附前后的电荷转移。这种电荷转移导致被吸附CO分子的活化。 关键词：

INVESTIGATION OF CO AND NO CHEMISORPTION ON THE Ⅷ GROUP TRANSITION METAL SURFACE BY Xα-DV METHOD(Ⅰ)——ELECTRONIC STRUCTURE OF CHEMISOPTION OF CO ON Rh(111) SURFACE

In this paper, the electronic structure of chemisorption of CO on Rh(lll) surface (θ≤l/3) has been calculated by the method of the self-consistent Hartree-Fock-Slater molecular cluster. The variation of the energy levels and total energy with respect to the vertical distance of the CO molecule above this surface is obtained. The optimized bond distance determined from the total energy curve is 1.85 ?, which is quite close to experimental result 1.95±0.1?. The binding energy is 0.98 eV, which is smaller than the experimental adsorption energy of 1.3 eV. The total density of states with above bond distance is calculated and it is in good agreement with the UPS result considering final state and relaxation effect. The bonding and antibonding character for the CO valence level have also been studied by analysis of the variations of the molecular eigenvalues when the CO molecule approaches the surface. The charge transfer for CO chemisorption on transition metal Rh is investigated through a Milliken population analysis and the analysis of coefficients of cluster wavefunction which is expanded by using CO molecular wavefunction. This charge transfer causes the activation of absorbed CO molecules.
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