Electronic and Magnetic Properties of Small Nickel Clusters and Their Interaction with CO Molecule
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ORIGINAL PAPER
Electronic and Magnetic Properties of Small Nickel Clusters and Their Interaction with CO Molecule Abdel-Ghani Boudjahem 1 & Mouhssin Boulbazine 1 & Meryem Derdare 1 Received: 28 July 2020 / Accepted: 13 October 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A theoretical study was performed onto the small nickel clusters in order to evaluate their stability and electronic and magnetic properties using density functional theory (DFT) calculations at the BLYP/Def2-TZVP level of theory. The adsorption of CO molecule over the surface of these clusters has also been investigated. The results show that the Ni6 and Ni8 clusters are more stable than their neighbors. The magnetic moments of these clusters are in the range of 0.67 to 1.33 μB/atom. The results reveal also that the local magnetic moment of 3d orbitals in Nin clusters plays a crucial role in the magnetism of the Nin clusters. The interaction between the clusters and the CO molecule was found to be very strong, and the calculated adsorption energies range from – 30.8 to – 44.6 kcal mol−1. Moreover, the electronic properties of these clusters are greatly changed upon adsorption process. The change in energy gap (ΔEg) of the Ni clusters is considerable, reflecting that these clusters are very sensitive to the presence of the CO molecule onto their surface. Thus the Nin clusters can be employed as nanosensors for the detection of the CO molecule. Keywords DFT . Nin clusters . CO adsorption . Electronic and magnetic properties
1 Introduction Due to their excellent catalytic properties as compared with the bulk metal, the transition metal (TM) nanoclusters have attracted much attention in the last two decades [1–6]. The physical properties of the TM clusters and their reactivity were mainly studied both experimentally and theoretically [7–12]. For example, nickel clusters are largely used as nanocatalysts in several catalytic reactions, especially in the hydrogenation of aromatic compounds [10, 13, 14]. They were also employed as efficient catalysts for the CO methanation reaction for the production of synthetic natural gas (SNG) [15]. Moreover, the nickel clusters showed a great catalytic activity and better stability in these catalytic reactions. As an example, the conversion of Ni clusters in benzene hydrogenation was found to be 100%, and their catalytic activity remains almost unchanged during 20 h [14]. The experimental results reveal
* Abdel-Ghani Boudjahem [email protected] 1
Computational Catalysis Group, Laboratory of Applied Chemistry, University of Guelma, Box 401, 24000 Guelma, Algeria
also that the reactivity of these clusters is greatly influenced by their particle size and their shape [15, 16]. In the hydrogenation of benzene, the small nickel clusters with size of 5 nm have a reactivity 5 times higher than that of the Ni clusters of 25 nm [14]. For the same reaction, the results show that the reactivity of the whisker-like nickel was found to be 4 times greater than that of the spherical-like
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