Far-IR Spectra of Small Neutral Gold Clusters in the Gas Phase

Gruene, Philipp; Butschke, Burkhard; Lyon, Jonathan T.; Rayner, D. M.; Fielicke, André

doi:10.1515/zpch-2014-0480

Cited by 53 publications

(83 citation statements)

References 61 publications

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“…The remaining 0.5% of the Au7 population is an assortment of other structures, indicative of the fluxional behavior of this system at 300 K. Nevertheless, for Au5-Au7 the impact of temperature on the isomer population is quite negligible up to 300 K, justifying the typical zero-kelvin modeling approach; however, for Au8 the impact of temperature at 300 K is already quite noticeable. In agreement with past FIR-MPD experiments at 100 K [66] and computational predictions at zero kelvin [43], our free-energy calculations predict Au8 prefers a planar 4-fold edgecapped square (D4ℎ) structure with P(100 K) = 100% (FIG. S6 of the SI).…”

Section: Free-energy Surfaces Of Au5-au13: Impact Of Temperature On Csupporting

confidence: 89%

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Two-to-three dimensional transition in neutral gold clusters: The crucial role of van der Waals interactions and temperature

Goldsmith

Florian

Liu

et al. 2019

Phys. Rev. Materials

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We predict the structures of neutral gas-phase gold clusters (Aun, n = 5-13) at finite temperatures based on free-energy calculations obtained by replica-exchange ab initio molecular dynamics. The structures of neutral Au5-Au13 clusters are assigned at 100 K based on a comparison of experimental far-infrared multiple photon dissociation spectra performed on Kr-tagged gold clusters with theoretical anharmonic IR spectra and freeenergy calculations. The critical gold cluster size where the most stable isomer changes from planar to nonplanar is Au11 (capped-trigonal prism, D3h) at 100 K. However, at 300 K (i.e., room temperature), planar and nonplanar isomers may coexist even for Au8, Au9, and Au10 clusters. Density-functional theory exchangecorrelation functionals within the generalized gradient or hybrid approximation must be corrected for longrange van der Waals interactions to accurately predict relative gold cluster isomer stabilities. Our work gives insight into the stable structures of gas-phase gold clusters by highlighting the impact of temperature, and therefore the importance of free-energy over total energy studies, and long-range van der Waals interactions on gold cluster stability.Metal clusters in the gas phase are widely used as model systems to study fundamental properties of condensed matter (see, e.g., Refs. [1][2][3][4][5][6][7]). At the nanoscale, gold is not a fully noble, nonreactive material; thus gold clusters are of particular interest due to their possible applications in gas sensing, pollution reduction, and catalysis [8][9][10][11][12][13][14][15][16][17]. Gold clusters in the gas phase exhibit many structural isomers of similar energetics and can rapidly interconvert among them [18][19][20][21][22][23][24]. Geometry and size can impact the physicochemical properties of clusters, for example, HOMO-LUMO gap, polarizability, and catalytic activity [25][26][27][28][29][30][31]. Small gold clusters often adopt stable planar geometries [32][33][34][35][36]. The critical size where gold clusters begin favoring nonplanar (three-dimensional, 3D) structures over planar (two-dimensional, 2D) structures has attracted sustained interest [37][38][39][40][41][42][43][44]. Gasphase ion-mobility experiments at room temperature suggest a transition from a 2D to 3D ground state structure at size 12 [45] and 8 [46] for negatively and positively charged clusters, respectively. Computational and experimental evidence supports these ground-state structural assignments for the 2D to 3D transition size [47,48]. For neutral gold clusters, computational studies predict their critical transition size is between Au10 and Au14 at zero kelvin [26,38,44], but experimental evidence is lacking due to the difficulty in spectroscopically characterizing neutral gas-phase clusters relative to charged clusters.Both experimental and computational studies indicate that dynamic structural rearrangements are a common feature among clusters at finite temperatures [22,[49][50][51][52][53][54][55][56][57]. It is clear that small go...

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Section: Free-energy Surfaces Of Au5-au13: Impact Of Temperature On Csupporting

confidence: 89%

“…By scanning the frequency of FELIX, mass selective FIR-MPD spectra of the Kr-tagged gold clusters are obtained from the IR induced intensity change I/I0 and plotted as experimental cross section 1/P lnI0/I with P being the IR laser power at a given wavenumber. More details on the experimental methods have been given before [66].…”

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confidence: 99%

Two-to-three dimensional transition in neutral gold clusters: The crucial role of van der Waals interactions and temperature

Goldsmith

Florian

Liu

et al. 2019

Phys. Rev. Materials

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“…The global minimum corresponds to a D 2h rhomboid‐like geometry, and the second most stable geometry to a C 2v Y‐like geometry, at only 0.041 eV above; both structures at singlet spin state. The theoretical description that the lowest energy isomer is the D 2h rhomboid one (Figure A) coincides with experimental and theoretical findings for neutral gold tetramer . Likewise, the theoretical descriptions also found that this structure is followed by some hundredths of eV by the C 2v Y‐like structure (see e.g., Ref.…”

Section: Methodssupporting

confidence: 84%

“…In this work, we offer a computational study to contribute in the answer of these questions by using neutral gold tetramer as a representative cluster. Au 4 has the advantage of being a much‐studied system from theoretical and experimental point of views . For example, it has been used as a viable and representative model of supported small clusters for dehydrogenation reactions .…”

Section: Introductionmentioning

confidence: 99%

Activation and diffusion of ammonia borane hydrogen on gold tetramers

Mejía

Ferraro

Osorio

et al. 2017

Int J of Quantum Chemistry

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One of the most serious candidates for safe storage of high hydrogen densities is ammonia borane, AB. Likewise, one of the most versatile catalysts known is gold in the form of atomic clusters. Taking these elements into account, in this work a density functional theory -based study about initial activation, detachment, and diffusion of ammonia borane hydrogen on gold tetramer, as a catalyst model, is developed. It was found that the total process is exergonic and that the hydrogen diffusion occurs with very low energy barriers. The process has a hydrogen detachment energy barrier lower than the one of the uncatalyzed AB, and that is easily overcome by the energy expelled in the previous stage of formation of the initial activated species. Additionally, all the process is assisted by the fluxionality of the gold cluster, and occurs via a unique catalytically activated initial species, which contains a three-center simultaneous interaction at the catalytically activated zone.ammonia borane, gold cluster catalyst, gold-fluxionality, theoretical study, three-center bonding | I N TR ODU C TI ONResearch about new ways for practical, safe, and economically convenient storage and release of large quantities of hydrogen in small volumes is today a very important issue. [1,2] Hydrogen has an energy content by mass almost three times superior to petroleum, [3] is the most abundant substance in the universe, is source-independent, and its combustion product, water, is environmentally friendly. Additionally, the availability of activated hydrogen is highly relevant for a large number of reactions in the chemical industry, where reduction or hydrogenation are necessary steps. [4,5] Among lightweight hydrogen storage materials, ammonia borane, AB (H 3 BNH 3 ), is a substance that contains large amounts of hydrogen (a total of 19.6 wt.%), [3] which is relatively easy to extract, either by direct or by assisted thermolysis, [6,7] by catalyzed room temperature solvolysis, [3,[8][9][10][11] or by other methods. [12][13][14][15] Additionally, AB can be easily and safely transported, [16] because, on the one hand, is a relatively stable solid at room conditions, [3,6,16] and is a substance soluble in many solvents, such as water, methanol, and tetraglyme. [3,[8][9][10][11][12] It has been found that the use of transition metals as catalysts in the AB dehydrogenation has the advantage of avoiding the expenditure of large amounts of energy, necessary for the hydrogen release. [7,[16][17][18] Even, in some cases, the catalysis has emerged as a solution to diminish the unwanted by-products of hydrogen release. [10,12,18] Transition metals of different nature, both noble and non-noble, as well as binary or tertiary combinations among them, have shown catalytic activity toward the extraction of hydrogen from AB. [3,[8][9][10][11][12]17,18] In the case of nanoparticles, the studies show that although some transition metals are better than others, the decrease in size (within certain limits and conditions [19] ) of the nanoparticles of the ...

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“…[1,2,3,4,5,6,7] It is known that relativistic effects on the electrons in gold lead to the hybridization of the 6s and 5d orbitals which generates several interesting properties such as the well documented 2dimensionality of cluster structures up to 13 atoms. [8,9,10,11,12,13,14] Gold clusters have been proposed for catalysis because of their high reactivity, partly due to the high surface to volume ratio. [15] Rhodium clusters have also been studied by several groups in recent years, [16,17,18,19,20,21] and have been found to possess large magnetic moments, this phenomenon is not observed in the bulk.…”

Section: Introductionmentioning

confidence: 99%

Study of the stability of small AuRh clusters found by a Genetic Algorithm methodology

Buendía

Vargas

Johnston

et al. 2017

Computational and Theoretical Chemistry

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Far-IR Spectra of Small Neutral Gold Clusters in the Gas Phase

Cited by 53 publications

References 61 publications

Two-to-three dimensional transition in neutral gold clusters: The crucial role of van der Waals interactions and temperature

Two-to-three dimensional transition in neutral gold clusters: The crucial role of van der Waals interactions and temperature

Activation and diffusion of ammonia borane hydrogen on gold tetramers

Study of the stability of small AuRh clusters found by a Genetic Algorithm methodology

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