The structure of nickel clusters

Parks, E. K.; Winter, Bernd; Klots, T. D.; Riley, S. J.

doi:10.1063/1.459910

Cited by 172 publications

(72 citation statements)

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“…In particular, it is expected that the dielectric constant of a bulk transition metal will not scale accurately to molecular dimensions, especially for small clusters (<10 2 atoms) for which packing structures not commensurate with that of the bulk lattice are often found [27]. The observation of metal cluster optical absorption spectra which differ appreciably from the classical prediction can be taken as one indication of a quantum size effect.…”

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confidence: 98%

Optical response of small niobium clusters

Knickelbein

Menezes

1992

Phys. Rev. Lett.

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The optical absorption spectra of small, isolated niobium clusters from seven to twenty atoms have been measured from 334 to 614 nm via photodepletion of niobium cluster-argon van der Waals complexes, Nb"Ar m , in a molecular beam. The absorption cross sections of all clusters in this size range increase with decreasing wavelength, as predicted by classical electrodynamic theory applied to small niobium spheres, however, the magnitudes of the cross sections are several times larger than predicted.PACS numbers: 36.40.+d, 33.20.Kf, 33.80.Gj, 82.80.Ms While small metal particles have been actively studied for many years, only recently have advances in metal cluster generation [1,2] permitted the investigation of the physical and chemical properties of unsupported metal clusters (M n ) of subnanometer dimensions, for n < 10 3 atoms. Yet, except for a few experimentally amenable systems [3][4][5][6][7][8][9][10][11], the measurement of size-specific optical absorption spectra of unsupported polyatomic metal clusters has proven to be an elusive goal due to several technical difficulties. Because metal clusters are typically generated in molecular beams at very low densities (< 10 10 cm" 3 ), direct absorption measurements are generally not possible. Furthermore, common methods of gas phase metal cluster generation usually produce a broad size distribution, thus severely complicating the assignment of the spectral carrier.The few gas phase absorption spectra obtained for polyatomic metal clusters have been recorded for weakly bound systems using the indirect method of photodissociation spectroscopy [3][4][5][6][7][8][9][10][11], in which photon absorption by M n is followed by rapid radiationless decay and ultimately fragmentation to M n -\+M, the extent of which is monitored mass spectrometrically as a function of wavelength. have been recorded using this technique, up to a few tens of atoms in some cases. However, because this method relies on the photodissociation of the clusters, it can only provide spectral information at wavelengths to the blue of their photodissociation thresholds, and is thus limited to relatively weakly bound clusters.For polyatomic transition-metal clusters, the experimentally determined dissociation threshold energies [12] are considerably higher than those of alkali, copper, and aluminum clusters, typically exceeding 3 eV and thus restricting the spectral range which could be investigated using photodissociation spectroscopy as described above. For small niobium clusters (Nb n ), the dissociation thresholds lie in the 5-6-eV range [13]. However, the same general approach can be exploited in the photodissociation of weakly bound rare gas van der Waals (vdW) complexes of metal clusters, M n R m , where the limitation imposed by the M n -\-M bond energy is circumvented. In this Letter we report the photodissociation action spectra resulting from argon atom loss following photoexcitation of Nb"Ar m vdW complexes for n =7-20: hv Nb" Ar w -Nb" + m Ar .The threshold for this process is expected ...

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confidence: 98%

Optical response of small niobium clusters

Knickelbein

Menezes

1992

Phys. Rev. Lett.

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“…Of the experimental studies on Ni N clusters, 29,30,31,32,33,34,35,36,37 the chemical-probe experiments 29,30,31,32,33,34,35,36 have given very valuable information on the structure of the smaller clusters. On the other hand, results for medium and large Ni clusters, 37 obtained by performing near-threshold photoionization and time-of-flight mass spectroscopy can be used in identifying particularly stable clusters and, subsequently, in providing information on growth modes.…”

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confidence: 99%

Structural and energetic properties of nickel clusters: 2⩽N⩽150

Grigoryan

Springborg

2004

Phys. Rev. B

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The four most stable structures of Ni N clusters with N from 2 to 150 have been determined using a combination of the embedded-atom method in the version of Daw, Baskes and Foiles, the variable metric/quasi-Newton method, and our own Aufbau/Abbau method. A systematic study of energetics, structure, growth, and stability of also larger clusters has been carried through without more or less severe assumptions on the initial geometries in the structure optimization, on the symmetry, or on bond lengths. It is shown that cluster growth is predominantly icosahedral with islands of fcc, tetrahedral and decahedral growth. For the first time in unbiased computations it is found that Ni 147 is the multilayer (third Mackay) icosahedron. Further, we point to an enhanced ability of fcc clusters to compete with the icosahedral and decahedral structures in the vicinity of N = 79. In addition, it is shown that conversion from the hcp/anti-Mackay kind of icosahedral growth to the fcc/Mackay one occurs within a transition layer including several cluster sizes. Moreover, we present and apply different analytical tools in studying structural and energetic properties of such a large class of clusters. These include means for identifying the overall shape, the occurrence of atomic shells, the similarity of the clusters with, e.g., fragments of the fcc crystal or of a large icosahedral cluster, and a way of analysing whether the N -atom cluster can be considered constructed from the (N − 1)-atom one by adding an extra atom. In addition, we compare in detail with results from chemical-probe experiment. Maybe the most central result is that first for clusters with N above 80 general trends can be identified.

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“…[14][15][16][17] Computer simulations of clusters have revealed a wide diversity of fundamental behavior that is highly sensitive to many factors, such as the cluster aggregate size N , the potential used to model the intermolecular interactions, and even the simulation method itself. The Lennard-Jones (LJ) potential is the most commonly used model potential for computer simulations of cluster properties, and it is especially useful for modeling rare gas clusters.…”

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confidence: 99%

Magic number behavior for heat capacities of medium-sized classical Lennard-Jones clusters

Frantz

2001

The Journal of Chemical Physics

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Monte Carlo methods were used to calculate heat capacities as functions of temperature for classical atomic clusters of aggregate sizes 25 ≤ N ≤ 60 that were bound by pairwise Lennard-Jones potentials. The parallel tempering method was used to overcome convergence difficulties due to quasiergodicity in the solid-liquid phase-change regions. All of the clusters studied had pronounced peaks in their heat capacity curves, most of which corresponded to their solid-liquid phase-change regions. The heat capacity peak height and location exhibited two general trends as functions of cluster size: for N = 25 to 36, the peak temperature slowly increased, while the peak height slowly decreased, disappearing by N = 37; for N = 30, a very small secondary peak at very low temperature emerged and quickly increased in size and temperature as N increased, becoming the dominant peak by N = 36. Superimposed on these general trends were smaller fluctuations in the peak heights that corresponded to "magic number" behavior, with local maxima found at N = 36, 39, 43, 46 and 49, and the largest peak found at N = 55. These magic numbers were a subset of the magic numbers found for other cluster properties, and can be largely understood in terms of the clusters' underlying geometries. Further insights into the melting behavior of these clusters were obtained from quench studies and by examining rms bond length fluctuations.

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The structure of nickel clusters

Cited by 172 publications

References 42 publications

Optical response of small niobium clusters

Optical response of small niobium clusters

Structural and energetic properties of nickel clusters: 2⩽N⩽150

Magic number behavior for heat capacities of medium-sized classical Lennard-Jones clusters

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