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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Structural Patterns in Carbon Chemisorption on an Icosahedral 2 Iron Cluster
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Structural Patterns in Carbon Chemisorption on an Icosahedral 2 Iron Cluster

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Carbon chemisorption on iron nanoparticles at small carbon coverage has been studied by using a Fe_(13) particle as a model because it possesses a nearly icosahedral geometry, and complications with additional effects associated with the surface inhomogeneity do not arise. The electronic and geo- metrical structures of Fe_(13) C_n are computed for n - 0—20 using an all-electron density functional theory with generalized gradient approximation and a rather large basis set. It is found that the energetically preferred structures correspond to the formation of carbon dimers up to Fe_(13)C_(12) and trimers up to Fe_(13)C_(18) in octahedral configurations of the dimers and trimers with the Fe_(13) cluster being endohedral. The trend for the formation of carbon tetramers breaks at Fe_(13)C_(20) We found that the dependence of the total energy on the total spin is nearly the same for Fe_(13) and Fe_(13)C8. When the number of chemisorbed carbon atoms exceeds 6, chemisorption quenches the total magnetic moment to 36 μ_B from the value of 44 μ_B in the ground-state Fe_(13) cluster. We used natural atomic orbital populations to understand why the quenching does not depend on the number of chemisorbed atoms. Free C? species were reoptimized at the same level of theory to calculate the dissociation energies of C_n and Fe_(13)C_n It is found that the largest fragmentation energy of 12 eV belongs to the Fe_(13) C_(12) → Fe_(13) + C_(12) channel. Finally, we found that atomization energies for the carbon chemisorbed on the iron particle are larger by approximately 10 eV than atomization energies of the corresponding free carbon particles, which can be related to the catalytic strength of the Fe_(13) particle.

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