Chemical Bonding of Transition‐Metal Co<sub>13</sub> Clusters with Graphene

Alonso-Lanza, Tomás; Ayuela, Andrés; Aguilera‐Granja, F.

doi:10.1002/cphc.201500692

Cited by 21 publications

(14 citation statements)

References 87 publications

(138 reference statements)

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“…50 The cobalt pseudopotential was described in detail and used to study Co 13 clusters adsorbed onto graphene in a previous study. 51 The basis sets for cobalt, hydrogen, and carbon were the double-polarized basis sets identified in previous studies.…”

Section: −1mentioning

confidence: 99%

Complex magnetic orders in small cobalt–benzene molecules

González

Alonso-Lanza

Delgado

et al. 2017

Phys. Chem. Chem. Phys.

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Organometallic clusters based on transition metal atoms are interesting because possible applications in spintronics and quantum information. In addition to the enhanced magnetism at the nanoscale, the organic ligands may provide a natural shield again unwanted magnetic interactions with the matrices required for applications. Here we show that the organic ligands may lead to non-collinear magnetic order as well as the expected quenching of the magnetic moments. We use different density functional theory (DFT) methods to study the experimentally relevant three cobalt atoms surrounded by benzene rings (Co3Bz3). We found that the benzene rings induce a ground state with non-collinear magnetization, with the magnetic moments localized on the cobalt centers and lying on the plane formed by the three cobalt atoms. We further analyze the magnetism of such a cluster using an anisotropic Heisenberg model where the involved parameters are obtained by a comparison with the DFT results. These results may also explain the recent observation of null magnetic moment of Co3Bz + 3 . Moreover, we propose an additional experimental verification based on electron paramagnetic resonance.

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Section: −1mentioning

confidence: 99%

Complex magnetic orders in small cobalt–benzene molecules

González

Alonso-Lanza

Delgado

et al. 2017

Phys. Chem. Chem. Phys.

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“…The structure and magnetism of free Co clusters has been studied in several papers using the density functional theory (DFT), 9,[23][24][25][26] and the properties of small Co clusters supported on graphene or graphene fragments have also been investigated. [27][28][29] To explore the possibility of widening the applications of cobalt clusters and nanoparticles, it is of interest to study their interaction with hydrogen. Co surfaces catalyze the Fischer-Tropsch reaction for the synthesis of liquid hydrocarbons, [30][31] and for this reason the adsorption of hydrogen on Co surfaces has been investigated.…”

Section: A Introductionmentioning

confidence: 99%

Theoretical study of the adsorption of hydrogen on cobalt clusters

García-Díez

Fernández-Fernández

Alonso

et al. 2018

Phys. Chem. Chem. Phys.

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Adsorption and dissociation of molecular hydrogen on transition metal clusters are basic processes of broad technological application in fields such as catalysis, hydrogenation reactions, hydrogen fuel cells, hydrogen storage, etc. Here we focus on two cobalt clusters, Co6 and Co13, and use the density functional formalism to investigate: (i) the mechanisms for adsorption and dissociation of hydrogen, and (ii) the competition between the two processes as the amount of hydrogen increases towards cluster saturation. The dissociative adsorption of hydrogen is the preferred adsorption channel for low coverage. Each individual H atom binds to the cluster with an ionic type of bonding, similar to that in metal hydrides. The electronic levels of the H atoms hybridize with the deepest levels of the Co cluster, leading to the stabilization of the system. In contrast H2 binds to the cluster with a weak covalent type of bond and the electronic density of the molecule becomes polarized. The electronic levels of the molecule are deeper than those of the Co cluster and do not hybridize with them, which explains the weak bonding of the molecule to the cluster. Interestingly, the high magnetic moments of the Co clusters do not change when H2 is adsorbed in molecular form, but the magnetic moments decrease by two Bohr magnetons upon dissociative adsorption of the molecule. Adsorption and dissociation of H2 on Co6 and Co13 exhibit similar features, although the adsorption energies on Co13 are stronger. Saturation of Co6 with hydrogen has been also investigated. Co6 can adsorb up to four H2 molecules in the dissociated form. Additional hydrogen is adsorbed in molecular form leading to a saturated cluster with sixteen hydrogen molecules, four dissociated and twelve molecular. This limit corresponds to a content of 8.4 wt% of hydrogen in the Co cluster, which is promising for the purpose of hydrogen storage.

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“…6 It has been widely established that graphene-based magnetic substrates are more stable and efficient than traditional transition metal based magnets. 7 Hence, 2D graphene materials have prospective applications for spintronic devices. Magnetism in graphene can be induced through intrinsic defects, 8 doping nonmetal 9,10 as well as transition metal impurities.…”

Section: Introductionmentioning

confidence: 99%