The chemical activation of the carbon monoxide (CO) molecule on the surface of iron clusters Fe_n (n = 1–20) is studied in this work. By means of density functional theory (DFT) all-electron calculations, we have found that the adsorption of CO over the bare magnetic Fe_n (n = 1–20) clusters is thermochemically favorable. The Fe_n–CO interaction increases the C–O bond length, from 1.128 ± 0.014 Å, for isolated CO, up to 1.251 Å, for Fe₉CO. Also, the calculated wavenumbers associated with the stretching modes ν_CO are decreased, or red-shifted, as another indicator of the CO bond weakening, passing from 2099 ± 4 to 1438 cm^–1. Markedly, wavenumbers of vibrational modes ν_CO agree admirably well in comparison with experimental results reported for Fe_nCO (n = 1, 18–20), getting small errors below 2.6%. The C–O bond is enlarged on the Fe_nCO (n = 1–20) composed systems, as the CO molecule increases its bonding, charge transference, and coordination with the iron cluster. Therefore, small bare iron particles Fe_n (n = 1–20) can be proposed to promote the CO dissociation, especially Fe₉CO, which has been proven to obtain the most prominent activation of the strong C–O bond by means of the charge transference from the metal core.

中文翻译：

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一氧化碳在小的铁磁性簇表面上的活化，Fe _n CO，n = 1-20。理论方法

在这项工作中研究了铁团簇Fe _n（n = 1-20）表面上的一氧化碳（CO）分子的化学活化。通过密度泛函理论（DFT）全电子计算，我们发现在裸露的Fe _n（n = 1-20）团簇上CO的吸附在化学上是有利的。中的Fe _Ñ -CO相互作用增加了CO键长，从1.128±0.014埃，对于分离CO，高达1.251埃，对于铁₉ CO，而且，使用拉伸模式ν相关联的波数来计算_CO减少，或红移，作为CO键减弱的另一个指标，范围从2099±4到1438 cm ^–1。显着地，振动模式ν的波数_CO相比同意极好以及与实验结果报道的Fe _Ñ CO（Ñ = 1，18-20），得到以下2.6％小的误差。当CO分子增加其键合，电荷转移以及与铁簇的配位时，在Fe _n CO（n = 1-20）组成的系统上C-O键增大。因此，可以建议使用小的裸铁颗粒Fe _n（n = 1-20）来促进CO的离解，尤其是Fe ₉ CO。事实证明，Fe ₉ CO可以通过强力的C-O键获得最显着的活化。金属芯的电荷转移。