Properties of isomers of the cluster Ni8 from density functional studies

Krger, Sven; Seemller, Thomas J.; Wrndle, Alexander; R��sch, Notker

doi:10.1002/1097-461x(2000)80:4/5<567::aid-qua5>3.0.co;2-d

Cited by 14 publications

(19 citation statements)

References 26 publications

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“…17,20,43 As is often the case, LDA values of the BE are larger than calculated at the GGA level and concomitantly bond distances are shorter. 1,5,16,28 Our calculated vertical and adiabatic IP (BP) values of the bare Ni 3 cluster, 6.48 and 6.29 eV, respectively, are 0.2-0.4 eV larger than experimental results of Knickelbein et al, 44 6.09 eV, and Watanabe, 45 6.12-6.16 eV. The vertical IP value calculated by Reddy et al, 30 6.38 eV, obtained with the frozencore GGA approach agrees with the present result, whereas the result of Pastor et al, 46 IP ) 6.2 eV, is closest to experiment, but was obtained with a tight-binding method without geometry optimization, using Ni-Ni distances fixed at the bulk nearestneighbor value, 249.2 pm.…”

Section: Discussionsupporting

confidence: 73%

“…Previous calculations showed that the cluster Ni 3 forms essentially an equilateral triangle with a Ni-Ni distance between 215 and 224 pm, depending on the employed computational approach (see Section IV.D). 30 As an initial step in our study, we also optimized the structure of bare Ni 3 with 16 (a 2 ′) 5 (e′) 40 (a 1 ′′) 1 (a 2 ′′) 6 (e′′) 16 with R(Ni-Ni) ) 223.2 pm and (a 1 ′) 16 (a 2 ′) 5 (e′) 39 (a 1 ′′) 2 (a 2 ′′) 6 (e′′) 16 with R(Ni-Ni) ) 225.6 pm. The electronic configuration (a 1 ) 36 (a 2 ) 9 (b 1 ) 14 (b 2 ) 25 in C 2V corresponds to the former configuration in D 3h symmetry; 32 it features the same BE per Ni atom, 175 kJ/mol, and a similar geometry: 33 Hence the two structures can be considered as equivalent.…”

Section: Resultsmentioning

confidence: 99%

“…Various experimental techniques have been developed to prepare and characterize transition metal clusters of specific nuclearity. One can obtain reliable experimental data for ionization potentials and electron affinities of neutral and charged clusters, the photoelectron spectrum, the polarizability, optical properties, magnetic moments, ligand adsorption capacities, etc. ,,− However, there is no experimental method for determining directly the structure of a metal cluster because clusters often are produced in gas-phase beams and they are too small (3−50 atoms) for applying diffraction techniques. Instead, an indirect chemical technique has often been applied for structural analysis that relies on the adsorption of probe molecules on metal clusters, e.g.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical Investigation of the Coordination of N₂ Ligands to the Cluster Ni₃

2004

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Various structures of complexes of the cluster Ni3 with 3 to 12 N2 ligands were modeled with a gradient-corrected density functional method. The stability of different types of bonding was considered and the most stable structures of Ni3(N2) x complexes (x = 3−9, 12) were determined for neutral, cationic, and anionic systems. For the most stable structure of the neutral complex with three and six N2 ligands, we calculated average ligand binding energies of 116 and 98 kJ/mol, respectively; the binding energy per ligand decreases with increasing number of ligand molecules. For canonical ensembles of mono- and trinuclear complexes with N2 ligands at varying molar ratio k = [N2]:[Ni3], our results suggest that, in agreement with experiment, the complex Ni3(N2)6 is among the dominating species at saturation; yet, at sufficiently large molar ratios k, the trinuclear complex with seven ligands, not observed in experiment, also plays an important role in the simulated distributions. It is unclear whether this partial discrepancy in the product distribution originates from complications to simulate the experimental situation or from some aspects of the experimental procedure. Coordination of more than seven N2 ligands is predicted to lead to a partial or full destruction of the Ni3 moieties into mononuclear N2 ligated complexes. The type of bonding of the N2 ligands (end-on, side-on, hapticity) was found to affect the characteristics of the complexes, e.g. the binding energy, the charge of the Ni3 moiety, and the activation of the ligands. End-on coordination of N2 molecules to a Ni atom of the Ni3 unit entails the most stable type of bonding, whereas side-on coordination causes a stronger elongation of N−N bonds. The ionization potential and the electron affinity of a Ni3 cluster were calculated to increase after association of ligands.

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Section: Discussionsupporting

confidence: 73%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Theoretical Investigation of the Coordination of N₂ Ligands to the Cluster Ni₃

2004

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“…Computational approaches also help to clarify bonding and magnetic properties of clusters as well as the spectral features of these systems [2][3][4][5][8][9][10][11][12][13][14][15][16][17][18] A model study of isomers of Ni 8 clearly suggested that such small transition metal clusters are rather flexible and have several isomers of similar stability. 19 Experimental information is even scarcer for metal clusters that contain impurities, especially non-metal atoms, because preparation and characterization of such clusters is more complicated. In the present work, we considered how single H, C, or O impurity atoms affect the structure and other properties of Ni 4 .…”

Section: Introductionmentioning

confidence: 99%

Structure, stability, electronic and magnetic properties of Ni4 clusters containing impurity atoms

Petkov

Vayssilov

Krüger

et al. 2006

Phys. Chem. Chem. Phys.

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Using a gradient-corrected density functional method, we studied computationally how single impurity atoms affect the structure and the properties of a Ni4 cluster. H and O atoms coordinate at a Ni-Ni bond, inducing small changes to the structure of bare Ni4 which is essentially a tetrahedron. For a C impurity, we found three stable structures at a Ni4 cluster. In the most stable geometry, the carbon atom cleaves a Ni-Ni bond of Ni4, binding to all Ni atoms. Inclusion of the impurity atom leads to a partial oxidation of the metal atoms and, in the most stable structures, reduces the spin polarization of the cluster compared to bare Ni4. An H impurity interacts mainly with the Ni 4s orbitals, whereas the Ni 3d orbitals participate strongly in the bonding with O and C impurity atoms. For these impurity atoms, Ni 3d contributions dominate the character of the HOMO of the ligated cluster, in contrast to the HOMO of bare Ni4 where Ni 4s orbitals prevail. We also discuss a simple model which relates the effect of a H impurity on the magnetic state of metal clusters to the spin character (minority or majority) of the LUMO or HOMO of the bare metal cluster.

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“…Whereas bare nickel clusters are magnetic [43][44][45][46], coordination of CO ligands leads to a reduction the magnetism or even to a complete quenching if all metal atoms are coordinated by a sufficient number of ligands, e.g. [Ni 6 (CO) 12 ] 2À or [Ni 48 Pt 6 (CO) 12 ] nÀ .…”

Section: Effect On the Cluster Magnetismmentioning

confidence: 99%